**Long-Term Outcomes of Induction Chemotherapy Followed by Chemo-Radiotherapy as Intensive Neoadjuvant Protocol in Patients with Esophageal Cancer**

**Nicola Simoni 1,\*,**†**, Michele Pavarana 2,**†**, Renato Micera 1, Jacopo Weindelmayer 3, Valentina Mengardo 3, Gabriella Rossi 1, Daniela Cenzi 4, Anna Tomezzoli 5, Paola Del Bianco 6, Simone Giacopuzzi 3, Giovanni De Manzoni 3,**‡ **and Renzo Mazzarotto 1,**‡


Received: 20 October 2020; Accepted: 30 November 2020; Published: 3 December 2020

**Simple Summary:** Neoadjuvant chemo-radiotherapy (nCRT) represents a standard approach for both Squamous Cell Carcinoma (SCC) and Adenocarcinoma (ADC) of the esophagus, leading to a 10–15% improvement in survival rate as compared with surgery alone in clinical trials. In this observational study, we report the efficacy and safety of an intensive nCRT protocol in the daily clinical practice, including 122 patients treated with induction chemotherapy, followed by concomitant chemo-radiotherapy, and surgery. Our findings showed good long-term survival and high pathological complete response (pCR) rates, with acceptable side-effects. Notably, the oncological outcome was the same in ADC and SCC responder patients. Although the nCRT protocol here reported represents a distinctive single-center experience, our results contribute to better define the role of an intensive neoadjuvant approach as a reliable therapy for the treatment of locally advanced esophageal cancer, and enrich the current literature on this challenging context.

**Abstract:** Background: A phase II intensive neoadjuvant chemo-radiotherapy (nCRT) protocol for esophageal cancer (EC) was previously tested at our Center with promising results. We here present an observational study to evaluate the efficacy of the protocol also in "real life" patients. Methods: We retrospectively reviewed 122 ECs (45.1% squamous cell (SCC) and 54.9% adenocarcinoma (ADC)) treated with induction docetaxel, cisplatin, and 5-fluorouracil (TCF), followed by concomitant TCF and radiotherapy (50–50.4 Gy/25–28 fractions), between 2008 and 2017. Primary endpoints were overall survival (OS), event-free survival (EFS) and pathological complete response (pCR). Results: With a median follow-up of 62.1 months (95% CI 50–67.6 months), 5-year OS and EFS rates were

54.8% (95% CI 44.7–63.9) and 42.7% (95% CI 33.1–51.9), respectively. A pCR was observed in 71.1% of SCC and 37.1% of ADC patients (*p* = 0.001). At multivariate analysis, ypN+ was a significant prognostic factor for OS (Hazard Ratios (HR) 4.39 [95% CI 2.36–8.18]; *p* < 0.0001), while pCR was a strong predictor of EFS (HR 0.38 [95% CI 0.22–0.67]; *p* < 0.0001). Conclusions: The nCRT protocol achieved considerable long-term survival and pCR rates also in "real life" patients. Further research is necessary to evaluate this protocol in a watch-and-wait approach.

**Keywords:** induction chemotherapy; chemo-radiotherapy; neoadjuvant treatment; esophageal cancer

#### **1. Introduction**

Esophageal Cancer (EC) represents a major health problem worldwide, ranking seventh among leading causes of cancer-related death [1]. Multimodal treatment, including chemotherapy, radiotherapy, and surgery, is currently accepted as standard of care for locally advanced stage disease [2,3]. Several randomized trials demonstrated a survival benefit with neoadjuvant chemo-radiotherapy (nCRT) followed by surgery, compared to surgery alone, both in patients with Squamous Cell Carcinoma (SCC) and Adenocarcinoma (ADC) of the esophagus and gastroesophageal junction (EGJ) [4–9]. Notably, responders to nCRT have a better prognosis than non-responders [10], and an intensification of the preoperative approach is often advocated to improve oncological outcomes [11].

In our previous experience, an intensive nCRT protocol was tested in a phase II trial, with encouraging results [12]. The nCRT protocol schedule consisted of an induction phase of weekly administered docetaxel, cisplatin, and 5-fluorouracil (TCF) for 3 weeks, followed by concomitant TCF administered weekly for 5 weeks along with radiotherapy (50–50.4 Gy in 25–28 fractions). Remarkably, a pathological complete response (pCR) was obtained in 47% of patients with a 5-year overall survival (OS) rate of 43% (77% for pCR group). These results could be explained by the use of a more intensive chemotherapy schedule and an increased radiotherapy dose compared to other preoperative approaches reported in the literature [6]. Based on these results, this protocol was considered the standard nCRT for both advanced esophageal SCCs and ADCs treated in our center.

However, since trial participants do not represent the population as a whole, applying this protocol in the daily practice could have led to poorer results. [13]. Based on this consideration, we performed a novel analysis of the efficacy and safety of this nCRT protocol in the daily clinical practice.

#### **2. Results**

#### *2.1. Baseline Characteristics*

A total of 122 consecutive patients were included in the analysis: 55 (45.1%) with SCC and 67 (54.9%) with ADC. Baseline characteristics are outlined in Table 1.


**Table 1.** Clinical and tumor characteristics of 122 patients.


**Table 1.** *Cont.*

IQR: interquartile range; SCC: squamous cell carcinoma; ADC: adenocarcinoma; BMI: body mass index; EGJ: gastroesophageal junction; \* clinical T stage not evaluable because of incomplete endoscopic ultrasound (EUS); § clinical stage TxN1; ◦ only patients who underwent surgery.

#### *2.2. Treatment Completion*

One hundred and nineteen (97.5%) patients underwent concurrent chemo-radiotherapy after the first induction phase, while three (2.5%) were excluded: two due to disease progression during induction chemotherapy, and one due to acute intestinal occlusion requiring surgery. One hundred and sixteen (97.5%) patients received the full prescribed radiation dose, while 3 (2.5%) did not complete the treatment schedule due to toxicity. In five (4.2%) patients the prescription dose was reduced to 45 Gy due to patient's frailty or to large field nodal volume. The median relative dose intensity (RDI) for the chemotherapy schedule was 0.86 (0.74–0.95). During the induction phase, no reduction in the administered chemotherapy doses was needed, and the average relative dose intensity (RDI) was 0.96 (0.88–1). Instead, during the concomitant phase, the average RDI was reduced to 0.77 (0.61–0.90), with a similar reduction for all drugs (average RDI 0.75 [0.57–0.88], 0.79 [0.60–0.91] and 0.75 [0.65–0.98] for docetaxel, cisplatin, and 5-fluorouracil, respectively). Table S1 (Supplementary Material) describes relative dose intensity (RDI), dose density, as well as nCRT protocol treatment details.

One hundred and seven (87.7%) patients underwent surgery. Radical resection (R0) was achieved in 105 patients (98.1% of resected patients). Table 2 reports details on surgery and pathological assessment.




**Table 2.** *Cont.*

PD: progression disease; nCRT: neoadjuvant chemoradiotherapy; IQR: interquartile range; LN: lymph node; TRG: tumor regression grade. § Patients evaluated for surgery after chemo-radiotherapy; \* watch-and-wait strategy following evidence of a complete response to nCRT protocol (bite-on-bite biopsies proven); ◦ 4 (4.1%) patients due to presumable nCRT toxicity and 1 (0.8%) patient for causes not tumor related; § information on TRG was missing in 19 patients (the sum of patients for this column does not match the total due to missing data); <sup>+</sup> McKeown procedure: Tri-incisional subtotal esophagectomy with cervical esophago-gastric anastomosis; # Ivor-Lewis procedure: partial esophagectomy with right intrathoracic esophago-gastrostomy; ˆ total gastrectomy and distal esophagectomy with intramediastinal anastomosis.

#### *2.3. Treatment Outcomes*

The estimated median follow-up time was 62.1 months (95% CI 49.0–67.6 months). Median OS and EFS of the entire cohort were 78.5 months (95% CI 42.3-NE [not estimable]) and 39.5 months (95% CI 27.3–82.6), respectively (Figure 1A,B), and increased in resected patients to 97.4 months (Hazard Ratios (HR) 0.24 95% CI 0.12–0.47, *p* < 0.0001) and 46.2 months (HR 0.28 95% CI 0.15–0.52, *p* < 0.0001), respectively. The OS rates at 1, 2, 3, and 5 years were 89.3% (95% CI 82.4–93.7), 77.8% (95% CI 69.4–84.2), 64.2% (95% CI 54.7–72.2), and 54.8% (95% CI 44.7–63.9), and the comparable EFS rates were 77.0% (95% CI 68.5–83.5), 60.7% (95% CI 51.4–68.7), 51.1% (95% CI 41.8–59.6), and 42.7% (95% CI 33.1–51.9), respectively. Median OS and EFS did not significantly differ between SCC versus ADC patients (Figure 1C,D).

**Figure 1.** Overall Survival (OS) and Event-Free Survival (EFS) estimated by Kaplan–Meier method. (**A**) OS and (**B**) EFS of the entire cohort; (**C**) OS and (**D**) EFS as a function of histotype (squamous cell carcinoma vs. adenocarcinoma).

#### *2.4. Pathological Complete Response*

Among resected patients, pCR was achieved in 51.4% (55/107) of patients, including 71.1% (32/45) of SCC and 37.1% (23/62) of ADC patients (*p* < 0.001). Median OS and EFS were particularly high in pCR cases, being 117 months (HR 0.30 95% CI 0.16–0.56, *p* < 0.0001) and 117 months (HR 0.35 95% CI 0.20–0.61, *p* < 0.0001), respectively (Figure 2A,B), with a similar trend for SCC and ADC patients (Figure 2C,D). The 3- and 5-year OS rates were 82.8% (95% CI 69.5–90.7) and 70.5% (95% CI 56.4–80.8), and the comparable EFS rates were 78.2% (95% CI 63.9–87.4) and 63.5% (95% CI 48.6–75.1), respectively, in pCR patients, as compared with 53.8% (95% CI 38.9–66.6) and 37.6% (95% CI 24.5–50.7), and 40.4% (95% CI 25.9–54.6) and 29.1% (95% CI 16.6–42.8) in non-pCR patients, respectively (*p* < 0.001). Tumor relapse occurred in 48 resected patients (44.9%), with a loco-regional pattern in 7 (6.5%) (Table S2, Supplementary Material).

In the univariate analysis, gender, pCR, pTstage, pNstage and Tumor Regression Grade (TRG) were significantly associated with OS and EFS (Table 3). In the multivariate analysis, pNstage remained a significant predictor for OS (the HR of pN1 cases with respect to pN0 cases was 4.39 (95% CI 2.36–8.18; *p* < 0.0001)), while pCR remained significant for EFS (the HR of pCR cases with respect to non-pCR cases was 0.38 (95% CI 0.22–0.67; *p* < 0.0001) (Table 3)).

**Figure 2.** (**A**) Overall Survival (OS) and (**B**) Event-Free Survival (EFS) estimated by Kaplan–Meier method as a function of pathological complete response (pCR vs. non-pCR) in resected patients. (**C**) OS and (**D**) EFS as a function of pCR and histotype (squamous cell carcinoma vs. adenocarcinoma). pCR: pathological complete response; SCC: squamous cell carcinoma; ADC: adenocarcinoma.

**Table 3.** Univariate and Multivariate Hazard Ratios (HR) and 95% CIs of factors associated with OS and EFS in resected patients.



**Table 3.** *Cont.*

OS: overall survival; EFS: event-free survival; HR: hazard ratio; CI: confidence interval; SCC: squamous cell carcinoma; ADC: adenocarcinoma; pCR: pathological complete response; TRG: tumor regression grade.

#### *2.5. Protocol Toxicity and Postoperative Complications*

Of the 119 (97.5%) patients who completed the nCRT protocol, 92 (77.3%) experienced at least one adverse event. Details of toxic effects are shown in Table 4. Thirty-two (26.9%) patients had grade ≥3 acute hematological toxicity, while 23 (19.3%) had acute grade ≥3 non hematological events. Overall, a potentially treatment-related death occurred in 4 (3.4%) patients.


**Table 4.** Neoadjuvant chemoradiotherapy protocol-related toxicity.

\* appearance or worsening; § neutropenic fever and sepsis; ◦ taxane-related skin reaction; <sup>ˆ</sup> heart failure; <sup>n</sup> requiring an intravascular stent implantation.

None of the patients who underwent surgery died within 30 days after resection or in-hospital. Fifty-nine (55.1%) patients had at least one post-operative complication (Table 5), most of which were mild [14]. Considering severe complications alone (Clavien Dindo ≥3b according to the Esophagectomy Complications Consensus Group [15]), 8 (7.3%) cases required reoperation or ICU. Of these, surgical serious events occurred in 5 (4.6%) patients while medical severe complications were reported in 3 (2.8%).


**Table 5.** Postoperative complications.

LOS: Length of Hospital Stay.

#### **3. Discussion**

Over the last 15 years, neoadjuvant chemo-radiotherapy and peri-operative chemotherapy have become the standard approaches for locally advanced EC, leading to a 10–15% improvement in long-term survival rates as compared with surgery alone in clinical trials [7–9,16]. However, which is the optimal strategy is still under debate. This observational study reports the efficacy and safety of an intensive nCRT protocol in the daily clinical practice for locally advanced EC. To the best of our knowledge, this study includes one of the largest cohorts of patients treated with induction chemotherapy, followed by chemo-radiotherapy, as the preoperative approach in EC. This nCRT protocol has previously been tested at our institution in a phase II trial, with good long-term survival (median OS 55 months) and pCR (47% of patients) [12]. The results of the present study, with an estimated median follow-up of 62.1 months, confirm the high OS and EFS rate (median 78.5 and 39.5 months, respectively) also in "real life" patients. This finding is relevant, and emphasizes the

efficacy, in terms of survival benefit, for neoadjuvant chemo-radiotherapy when added to surgery in patients with EC.

Noteworthy, pCR was achieved in 51.4% of resected patients, one of the highest percentages reported so far [17]. Indeed, a pCR is considered one of the best available predictors of outcome for EC patients who undergo chemo-radiation therapy followed by esophagectomy [18,19]. A recent MDACC cohort study showed that pCR was associated with an improved survival (median OS 71.28 months for pCR versus 35.87 for non-pCR cases, *p* = 0.002) [10]. Of the 911 treated patients, 218 (23.9%) achieved a pCR, with a rate of 32.2% for SCC and of 23.1% for ADC (*p* = 0.06). In our study, pCR patients achieved a 5-year OS rate of 70.5% (versus 37.6% in non-pCR patients), with a similar survival trend for SCC and ADC responder patients (Figure 2C,D). This result supports the role of pCR as a trustworthy surrogate predictor marker of survival advantage.

In the ChemoRadiotherapy for Oesophageal cancer followed by Surgery Study (CROSS) trial, pCR rate was 29%, with a significantly larger number of SCC patients (49% versus 23% for ADC, *p* = 0.008) [7]. In our study, 32 of 45 (71.1%) SCC patients had a pCR in the surgical specimen. This percentage is remarkable and confirms the greater sensitivity of SCC to full-dose chemo-radiotherapy as previously reported by other authors [20]. Another issue is whether surgery on demand is advisable in selected clinical complete responder patients. In a subgroup analysis of our study, we found that the percentage of pCR was significantly higher for SCC vs. ADC tumors (17/21, 81% vs. 4/16, 25%, *p* = 0.002) in females, while no significant difference was observed in males (15/24, 63% for SCC vs. 19/46, 41% for ADC, *p* = 0.15). Moreover, in patients with a pCR, median OS and EFS were particularly high in females (not achievable versus 82.6 months in males, *p* = 0.01, and not achievable versus 33.6 months in males, *p* = 0.002, respectively). Based on these results, the female population with SCC seems to be the ideal candidate for a watch-and-wait approach. The ongoing randomized SANO trial, comparing salvage surgery with immediate surgery in clinical complete responders after nCRT, will provide results over the next few years [21,22].

Controversy exists over the optimal neoadjuvant approach for gastroesophageal junction (EGJ) adenocarcinomas [23]. Neoadjuvant chemo-radiation is associated with an increased local control of the tumor compared with perioperative chemotherapy alone, but this does not translate into an increased survival [24]. Furthermore, the pCR rates in ADCs treated with chemo-radiotherapy are significantly worse than SCCs, being less than 20–25% [6,7,20]. An increase in pCR rate, correlated with the use of higher doses of radiotherapy, compared to 41.4 Gy used in the CROSS trial [7], has been described in the literature. In detail, the use of doses between 45 and 50.4 Gy, in combination with carboplatin-paclitaxel, produced a pCR in 29–36% of treated patients, with acceptable toxicity [25–27]. In our series the pCR rate for ADCs was noticeably high, being 37.1%, and in this subset of patients both median OS and EFS were 117 months. This may be due to the use of an intensive schedule with docetaxel, cisplatin plus 5-fluorouracil (5-FU) during the induction phase and concomitant with radiotherapy (RT), as well as to the 50–50.4 Gy dose administered in this protocol that could have helped maximize local response. This finding further supports the potential effectiveness and generalizability of the use of nCRT in ADC of the esophagus, as a reliable or even better alternative to perioperative chemotherapy in selected patients, although the design of the study does not permit to draw definitive conclusions, due to the lack of a control group [28]. However, many ADCs are extremely resistant to chemo-radiotherapy: these ADC patients may not benefit from this treatment but are exposed to its negative consequences such as toxicity and delayed surgical therapy. To this regard, a multicenter, randomized phase II study on BIRC3-expression driven therapy (nCRT versus upfront surgery), in patients with resectable ADC of the esophagus and EGJ, is currently ongoing (BoRgES trial, NCT04269083) at the authors' institution.

According to the literature [29], this study confirms that nodal downstaging (ypN0) is a strong predictor for OS. We can assume that nodal response might be as important as downstaging on the primary tumor, and that a poor nodal response cannot be compensated even by radical surgery, thus representing a reliable biological marker for poorer survival. Instead, pCR remains the predominant prognostic factor for EFS, presumably indicating that complete response to nCRT corresponds to a

particularly favorable tumor biology or treatment efficacy or both. This latter finding is particularly intriguing for the squamous histology. As mentioned above, if the pCR rate is extremely high in this subgroup, and the consequent EFS markedly prolonged, close observation with salvage surgery might be an embraceable option to improve patients' quality of life (QoL) [30].

One potential criticism regarding the use of this intensive nCRT protocol is toxicity, leading to death in about 3% of treated patients. Thus, its use should be recommended only in specialized centers. However, the vast majority of patients were able to complete the planned preoperative treatment, and, notably, the subsequent surgery was not jeopardized by the nCRT protocol. The R0 surgical rate is also remarkable, amounting to 98.1% of resected patients (86.1% for the entire cohort). Hence, considering that tumor shrinkage after nCRT can significantly increase the R0 resection rate that 73.8% of patients achieved a ypN0 and 51.4% a pCR, and that nCRT adverse events did not represent a contraindication for surgery, we can assert that the protocol survival benefit was not counteracted by an excessive toxicity.

Our study presents some limitations. Indeed, it is an observational study, with a 10-year enrollment period, during which some variations in diagnostic accuracy, management of patients and post-operative surveillance occurred. Moreover, the indication to the nCRT protocol was defined on the basis of our previous experience and as a distinctive practice of our multidisciplinary team, thus our results could be biased by the patient selection process. Finally, this analysis included different histologies (SCC and ADC), which could have added heterogeneity to the outcomes measured.

#### **4. Materials and Methods**

#### *4.1. Study Design*

This study is an Institutional Review Board (IRB)-approved (Number DBCES001) observational single-center analysis of prospectively collected data, designed to assess the real-life effectiveness and safety of our nCRT protocol in patients with SCC and ADC of the esophagus and gastroesophageal junction. We considered all consecutive patients treated at our Institution from January 2008 to December 2017. The following perioperative data were collected: baseline demographics, diagnostic work-up, neoadjuvant protocol details, intra-operative findings, and post-operative data. According to the main international guidelines [2], patients with Siewert III type tumors were treated as gastric cancers, while patients with SC cervical tumors were assigned to definitive chemo-radiotherapy and therefore excluded from the analysis.

#### *4.2. Staging*

The pre-treatment staging consisted of clinical examination, blood chemistries including tumor markers, contrast-enhanced total body CT scan, fluorodeoxyglucose positron-emission tomography ( 18FDG-PET/CT), esophagogastroduodenoscopy with biopsies, and endoscopic ultrasound (EUS). In SCC patients, tracheobronchoscopy, esophageal magnetic resonance (MR), and cervical ultrasound were also performed. Patients were staged according to the Union for International Cancer Control [UICC] TNM cancer staging [31] and the therapeutic approach was defined by the institutional multidisciplinary tumor board.

#### *4.3. Chemo-Radiotherapy Schedule*

Treatment schedule consisted of a first phase of induction chemotherapy for 3 weeks (days 1–22), followed by a second phase of concurrent chemotherapy and radiotherapy for 5 weeks (days 29–63), as previously described [12]. Briefly, the chemotherapy treatment plan was as follows: docetaxel 35 mg/m2 and cisplatin 25 mg/m<sup>2</sup> on days 1, 8, 15, 29, 36, 43, 50 and 57 plus 5 fluorouracil (5-FU) 180 mg/m2 as protracted venous infusion (c.i.) on days 1 to 21 and 150 mg/m2 c.i. on days 29 to 63. The detailed treatment schedule is represented in Table S3 (Supplementary Material).

Radiation therapy (RT) was delivered concurrently with chemotherapy starting on day 29. The prescribed dose was 50–50.4 Gy delivered in 25–28 fractions. The gross tumor volume (GTV) included the primary lesion and any regionally involved lymph nodes. The GTV was contoured using data from CT scan, EUS, and PET/CT fusion scans. The clinical target volume (CTV) was generated by expanding the GTV tumor by 3 cm cranially and caudally and 1 cm radially, while positive lymph nodes were uniformly expanded by 1 cm. The CTV was usually completed with the addition of the elective nodal irradiation (ENI) volume [32]. A CTV-to-PTV margin of 8–10 mm was applied. Until 2013, RT was delivered using three-dimensional conformal radiotherapy (3D-CRT). From 2014, 3D-CRT was replaced by intensity-modulated radiotherapy (IMRT) and volumetric modulated arc radiotherapy (VMAT). Image-guided radiation therapy (IGRT) was routinely used.

#### *4.4. Restaging, Surgery and Pathological Analysis*

Patients were restaged with pretreatment work-up procedures between the fourth and fifth week after treatment completion. Response evaluation was performed using response evaluation criteria in solid tumors (RECIST and PERCIST Criteria) [33,34]. Surgery with radical intent was performed 6 to 8 weeks after nCRT completion. A Two- or 3-field lymph node dissection was performed based on tumor site and clinical nodal status at diagnosis. Abdominal D2 and standard mediastinal lymphadenectomy was the standard approach for ADC. Extension to the recurrent nerve chain nodes or a complete 3-field lymphadenectomy was performed for SCC based on node involvement. Peritoneal lavage cytology was evaluated in all ADC patients. Positive cytology was considered to be metastatic. Surgical complications were registered according to Clavien Dindo Classification [15]. A positive resection margin (R1) was defined as vital tumor cells within 1 mm of the proximal and distal resection margins, while a circumferential margin was considered involved if neoplastic cells were found at the cut margin. Pathological complete response (pCR) was defined as no vital tumor cells in the resection specimen (ypT0N0M0), and Tumor Regression Grade (TRG) was scored according to a modified Mandard score system [35].

#### *4.5. Follow-Up*

Follow-up examination was performed every 6 months after surgery for resected cases and every 3 months after nCRT protocol completion for non-resected patients. The follow-up schedule included: total body contrast-enhanced CT scan, esophagogastroscopy, tumor markers, neck endoscopic ultrasound in SCC and a clinical assessment. Toxicity data were collected during follow-up according to common terminology criteria for adverse events (CTCAE) version 4.0 [36].

#### *4.6. Statistical Analysis*

Quantitative variables were described as median and interquartile range (IQR) or mean and standard deviation (SD), categorical variables were summarized as counts and percentages. The median follow-up time was based on the reverse Kaplan-Meier estimator. Primary endpoints considered were OS, event-free survival (EFS) and pCR. Secondary endpoint was toxicity.

OS was the time from the start of induction chemotherapy to death, and EFS was calculated from the start of induction chemotherapy to the date of a documented disease progression, relapse, or death. Patients who did not develop an event during the study period were censored at the date of last observation. The survival probabilities were estimated using the Kaplan-Meier method and reported with their 95% confidence interval (CI). Comparisons among strata were performed using the log-rank test. Hazard ratios (HR) and 95% CI for each group were estimated using univariate Cox proportional hazards models. No deviation from the proportional hazards assumption were found by the numerical methods of Lin et al. [37]. The independent role of each covariate in predicting survival was verified in a multivariable model considering all characteristics significantly associated with the outcome in the univariate analyses. Associations were assessed using the χ2 or Fisher exact test as appropriate. All statistical tests were two-sided and a *p* value <0.05 was considered statistically significant. Statistical analyses were performed using the RStudio (RStudio: Integrated Development for R. RStudio Inc., Boston, MA, USA).

#### **5. Conclusions**

In conclusion, this intensive neoadjuvant schedule with induction chemotherapy followed by chemo-radiotherapy, based on docetaxel, cisplatin, 5-fluorouracil, and 50–50.4 Gy radiotherapy, achieves considerable results in terms of survival and pCR rate also in "real life" patients, largely counterbalancing the risk of not negligible adverse events. Noteworthy, the protocol does not jeopardize the achievement of radical resection and does not increase the rate of postoperative complications. Further studies are necessary to evaluate the use of this protocol also in a watch-and-wait approach.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2072-6694/12/12/3614/s1. Table S1. Neoadjuvant chemo-radiotherapy protocol details. Table S2. Incidence and pattern of failure distribution among resected patients (first site of recurrence). Table S3. Neoadjuvant chemo-radiotherapy protocol schedule.

**Author Contributions:** Conceptualization, N.S.; methodology, N.S. and M.P.; software, P.D.B.; validation, S.G., G.D.M. and R.M. (Renzo Mazzarotto); formal analysis, N.S., J.W. and P.D.B.; data curation, M.P., R.M. (Renato Micera), V.M., and G.R.; writing—original draft preparation, N.S., R.M. (Renato Micera) and J.W.; writing—review and editing, V.M., D.C., A.T., P.D.B., and S.G.; supervision, G.D.M. and R.M. (Renzo Mazzarotto). All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest

#### **References**


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### *Article* **Significance of Lauren Classification in Patients Undergoing Neoadjuvant/Perioperative Chemotherapy for Locally Advanced Gastric or Gastroesophageal Junction Cancers—Analysis from a Large Single Center Cohort in Germany**

**Rebekka Schirren 1, Alexander Novotny 1, Christian Oesterlin 1, Julia Slotta-Huspenina 2, Helmut Friess <sup>1</sup> and Daniel Reim 1,\***


**Simple Summary:** Chemotherapy ahead of surgery is standard of care for locally advanced stomach cancer or cancer at the junction between esophagus and stomach in Europe. However, response to chemotherapy may depend on microscopic features of the tumor. Three types were defined before: intestinal, diffuse and mixed types. The authors aimed to investigate if these characteristics influence survival after end of treatment (chemotherapy+surgery) in a large cohort treated in a University hospital. It was found that intestinal type patients demonstrate longer survival after chemotherapy+surgery than those with diffuse types. In the mixed type group no clear conclusion regarding the effect of chemotherapy ahead of surgery may be taken. Conclusively, patients with diffuse type tumors do not benefit from chemotherapy ahead of surgery.

**Abstract:** Background: the purpose of this analysis was to analyze the outcomes of multimodal treatment that are related to Lauren histotypes in gastro-esophageal cancer (GEC). Methods: patients with GEC between 1986 and 2013 were analyzed. Uni- and multivariate regression analysis were performed to identify predictors for overall survival. Lauren histotype stratified overall survival (OS)-rates were analyzed by the Kaplan–Meier method. Further, propensity score matching (PSM) was performed to balance for confounders. Results: 1290 patients were analyzed. After PSM, the median survival was 32 months for patients undergoing primary surgery (PS) and 43 months for patients undergoing neoadjuvant chemotherapy (nCTx) ahead of surgery. For intestinal types, median survival time was 34 months (PS) vs. 52 months (nCTx+surgery) *p* = 0.07, 36 months (PS) vs. (31) months (nCTx+surgery) in diffuse types (*p* = 0.44) and 31 months (PS) vs. 62 months (nCTx+surgery) for mixed types (*p* = 0.28). Five-/Ten-year survival rates for intestinal, diffuse, and mixed types were 44/29%, 36/17%, and 43/33%, respectively. After PSM, Kaplan–Meier showed a survival benefit for patients undergoing nCTx+surgery in intestinal and mixed types. Conclusion: the Lauren histotype might be predictive for survival outcome in GEC-patients after neoadjuvant/perioperative chemotherapy.

**Keywords:** gastric/gastroesophageal cancer; perioperative chemotherapy; Lauren histotype

#### **1. Introduction**

Gastric cancer belongs to the most common malignant diseases worldwide with the highest incidence in Eastern Asia [1]. Despite decreasing incidence in the West, it

**Citation:** Schirren, R.; Novotny, A.; Oesterlin, C.; Slotta-Huspenina, J.; Friess, H.; Reim, D. Significance of Lauren Classification in Patients Undergoing Neoadjuvant/Perioperative Chemotherapy for Locally Advanced Gastric or Gastroesophageal Junction Cancers—Analysis from a Large Single Center Cohort in Germany. *Cancers* **2021**, *13*, 290. https:// doi.org/10.3390/cancers13020290

Received: 1 December 2020 Accepted: 31 December 2020 Published: 14 January 2021

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remains a therapeutic challenge. In the Western hemisphere gastric malignancy is often diagnosed at an advanced stage and, in contrast to Eastern Asia, it is preferably located in the proximal third of the stomach or the gastro-esophageal junction (GEJ) [2]. Hence, multimodal treatment concepts have been introduced after demonstrating outcome benefits in randomized controlled trials [3–5]. Nevertheless, not all patients are benefitting from neoadjuvant or perioperative chemotherapy, depending on localization, regimen, and also on the histological subtype. In the past, a signet ring cell, like gastric cancer, was identified to be non-responsive to neoadjuvant chemotherapy [6,7]. However, the data published so far have been difficult to interpret, as there were numerous definitions on the histology of signet ring cell or signet ring cell, like gastric cancer [8]. A pragmatic and feasible sub-classification was only recently published [9]. However, none of the prospective trials investigating the value of neoadjuvant chemotherapy applied this classification system before. Therefore, it is of special interest if already established histopathological classifications may stratify and identify patients to benefit from neoadjuvant/perioperative chemotherapy. This may be accomplished by the widely accepted Lauren classification, because all of the relevant histopathological subtypes (signet ring cell type, poorly-cohesive signet ring cell type, poorly cohesive non-signet-ring cell type, mucinous, papillary, and tubular) are summarized here [10]. Therefore, it was hypothesized that the Lauren histotype dependent histopathologic response may influence survival outcomes after neoadjuvant/perioperative chemotherapy and the aim of this analysis was to evaluate the oncologic outcomes of perioperative/neoadjuvant chemotherapy in a large German single center cohort, depending on the Lauren histotype.

#### **2. Results**

For this retrospective analysis, the institutional database for gastric cancer patients was screened and identified 2782 patients having been treated by either surgery or chemotherapy followed by surgery. After removing all cases not fulfilling the defined inclusion criteria (n = 1573), 1209 patients were included in this analysis. 730 patients underwent primary surgery and 479 underwent neoadjuvant/perioperative chemotherapy ahead of surgery. Overall, 663 were diagnosed with Lauren intestinal (398 surgery, 265 nCTx), 359 Lauren diffuse (216 surgery, 143 nCTx), and 187 Lauren mixed type (116 surgery, 71 nCTx). In the entire patient cohort, 247 patients received PLF (20.4%), 41 patients PLF+Taxol (3.4%), 53 (4.4%) OLF, 47 (3.9%) MAGIC, 17 (1.4%) FLOT, and 63 patients received modified regimens (5.2%). The analysis of the baseline characteristics showed significant differences between the primary surgery and neoadjuvant/perioperative chemotherapy group regarding gender distribution (more female patients for intestinal and diffuse. but not mixed Laurentype), older age for patients undergoing primary surgery (all Lauren subtypes), higher proportion of distal cancer locations in primary surgery patients (all groups, especially intestinal type), less advanced cT-stages in the surgery only group (cT2 vs. cT3/4 over all Lauren subtypes), earlier clinical stages, higher proportion of patients requiring extension to the distal esophagus in the chemotherapy group (all Lauren subtypes), higher D2 rates and higher median number of dissected lymph-nodes (LN) in patients undergoing direct surgery (especially in intestinal and mixed Lauren histotype, not so in diffuse type), more pT4a cancers in the primary resection group for all of the Lauren subtypes, earlier UICC stages in those patients undergoing neoadjuvant/perioperative chemotherapy. The proportion of Lauren subtypes, histiopathologic grading, R0-status, and complication rates were balanced between the groups. The histopathologic response rates (Becker Ia/Ib) were 22% in Lauren intestinal type, 9% in Lauren diffuse type, and 21% in Lauren mixed type tumors. Tables 1–3 depict the complete baseline characteristics.


**Table 1.** Baseline characteristics for patients with intestinal Lauren subtype before and after propensity score matching (PSM).


**Table 1.** *Cont.*

Legend: cT1 = Mucosa/Submucosa; cT2 = Muscularis propria; cT3 = Serosa; cT4 = Adjacent organs; cN0 = no lymph nodemetastasis detected during staging, cN+ = locoregional lymph node metastasis evident during staging; CD = Clavien Dindo Classification; Staging according to UICC 8th edition; *p*-values printed in bold are considered statistically significant.

**Table 2.** Baseline characteristics for patients with diffuse Lauren subtype before and after PSM.



**Table 2.** *Cont.*

Legend: cT1 = Mucosa/Submucosa; cT2 = Muscularis propria; cT3 = Serosa; cT4 = Adjacent organs; cN0 = no lymph nodemetastasis detected during staging, cN+ = locoregional lymph node metastasis evident during staging; CD = Clavien Dindo Classification; Staging according to UICC 8th edition; *p*-values printed in bold are considered statistically significant.


**Table 3.** Baseline characteristics for patients with mixed Lauren subtype before and after PSM.


**Table 3.** *Cont.*

Legend: cT1 = Mucosa/Submucosa; cT2 = Muscularis propria; cT3 = Serosa; cT4 = Adjacent organs; cN0 = no lymph nodemetastasis detected during staging, cN+ = locoregional lymph node metastasis evident during staging; CD = Clavien Dindo Classification; Staging according to UICC 8th edition; *p*-values printed in bold are considered statistically significant.

> The median follow-up was 30 months (range 1–242 months), comprising of 61 months (range 1–242 months) for survivors and 19 months (range 1–183) months for deceased patients. During the follow-up period 658 patients (54.4%) died, the five-year survival rate was 42%, the ten-year survival rate was 32%. Median survival was 38 months for patients undergoing primary surgery and 46 months for patients undergoing chemotherapy ahead of surgery (*p* = 0.06). Five-year survival rates (FYSR)/ten-year survival rates (TYSR) after primary surgery and after neoadjuvant/perioperative chemotherapy followed by surgery were identical (44/33%). The UICC stage dependent analysis revealed that this effect was only reproducible in UICC stage III (19 vs. 24 months median survival, *p* = 0.03), but not in the other UICC stages (UICC I: median survival not met, *p* = 0.58; UICC II: median survival 72 (surgery) vs. 57 (nCTx+surgery) months, *p* = 0.7). In patients with Lauren intestinal subtype, the median survival time was 51 months (45 months for primary surgery vs. 57 months for neoadjuvant/perioperative chemotherapy + surgery, *p* = 0.025), in the diffuse type group 33 months (35 months for primary surgery vs. 28 months for neoadjuvant/perioperative chemotherapy + surgery, *p* = 0.16) and 40 months (26 months for primary surgery vs. 62 months for neoadjuvant/perioperative chemotherapy + surgery, *p* = 0.05) in the Lauren mixed type group. FYSR and TYSR for patients with Lauren intestinal, diffuse, and mixed subtype were 48/35%, 39/31%, and 42/32%, respectively.

> The following variables were included in the cox regression analysis: age, gender, localization, neoadjuvant/perioperative chemotherapy, UICC-stage, Lauren subtype, number of dissected LN, R-stage, grading, and postoperative complications, because these are the most relevant factors in predicting survival. The pT- and pN-stages were not included, as these factors are summarized in the UICC-stage. All of the factors were entered in the multivariate model without selection. Univariate regression analysis revealed age, tumor location (all locations), all UICC-stages, Lauren intestinal and diffuse subtypes, R-status, grading, and the occurrence of postoperative complications to be significantly associated with post-therapeutic survival (Table 4). The multivariate analysis demonstrated that age, localization (proximal, middle, distal), application of neoadjuvant/chemotherapy, all UICC-stages, all Lauren subtypes, R-stage, and occurrence of postoperative complications were significantly and independently related to postoperative survival. Because of the imbalanced baseline characteristics, propensity score matching (PSM) was performed, and further analysis was performed on the PS-matched cohorts.


**Table 4.** Univariate and Multivariate regression analysis for overall survival (OS).

Legend: HR = Hazard Ratio, CI95% lower: 95% Confidence Interval lower boundary, CI95% upper: 95% Confidence Interval upper boundary, *p* = *p*-value, ! male vs. female; \$ categorical variable, first value is reference (=1.00): Localization, UICC-stage, Lauren subtype, Clavien Dindo grade; *p*-values printed in bold are considered statistically significant.

#### *Results after PSM*

Those variables demonstrating clinically meaningful baseline differences within the respective Lauren subgroups were matched through PSM (age, gender, location, clinical stage, UICC stage) in order to balance possible confounders (Supplementary Figure S1). The matching algorithm matched 170 patients each (surgery/nCTx+surgery) in the Lauren intestinal, 105 patients each in the Lauren diffuse, and 56 patients each in the Lauren mixed subtype groups. Analysis of the baseline characteristics demonstrated that the following variables were then well balanced in all of the groups: Gender, age distribution, tumor localization, clinical stages, D2 dissection rate, number of dissected LN, postop complications, pT-stages (in the Lauren intestinal and mixed, not in the diffuse subtype), UICC (intestinal and mixed subtypes, not diffuse), and grading and R0 status. Tables 1–3 show the results.

Median follow-up was 26 months (range 1–242 months), comprising of 55 months (range 1–242 months for survivors and 16 months (range 1–144) months for deceased patients. During the follow-up period, 367 patients (55.4%) died, the five-year survival rate was 41%, and the ten-year survival rate was 25%. The median survival was 32 months for patients undergoing primary surgery and 43 months for patients undergoing chemotherapy ahead of surgery (*p* = 0.16). FYSR/TYSR after primary surgery and after neoadjuvant/perioperative chemotherapy, followed by surgery were 42/31% and 44/32%. The UICC stage dependent analysis revealed no significant survival differences for UICC stages I and II (UICC I: median survival not met, *p* = 0.33; UICC II: median survival 91 (surgery) vs. 80 (nCTx+surgery) months, *p* = 0.72). In UICC III, there was a statistically significant survival difference in favor of those patients undergoing neoadjuvant/perioperative

chemotherapy (median survival 18 (surgery) vs. 26 (nCTx+surgery) months (*p* = 0.02), Figures S2–S4. In patients with Lauren intestinal subtype, the median survival time was 46 months (34 months for primary surgery vs. 52 months for neoadjuvant/perioperative chemotherapy + surgery, *p* = 0.07), in patients with diffuse subtype group 35 months (36 months for primary surgery vs. 31 months for neoadjuvant/perioperative chemotherapy + surgery, *p* = 0.44) and 57 months (31 months for primary surgery vs. 62 months for neoadjuvant/perioperative chemotherapy + surgery, *p* = 0.28) in patients with the Lauren mixed subtype. FYSR/TYSR for Lauren intestinal, diffuse, and mixed subtypes were 44/29%, 36/17%, and 43/33%, respectively. Kaplan–Meier analysis revealed that survival benefit for those patients undergoing neoadjuvant/perioperative chemotherapy was detectable for Lauren intestinal (*p* = 0.07) and mixed types (0.28) without statistical significance (Figures 1 and 2). The overall survival was (statistically not significantly) worse for Lauren diffuse type gastric cancer patients when undergoing neoadjuvant/perioperative chemotherapy (*p* = 0.44), (Figure 3). A survival benefit was detectable for Lauren intestinal type patients revealing histopathologic response (HPR) (median survival unmet vs. 43 months in nonresponders and 34 months in patients undergoing primary surgery, *p* = 0.01) (Figure 4). There was no significant survival difference between patients undergoing primary surgery and non-responders to nCTx (*p* = 0.65) (Figure 4). This was not reproducible in Lauren diffuse type patients: The median survival was 21 months in responders vs. 33 months in non-responders (*p* = 0.52) and 36 months in patients undergoing primary surgery (*p* = 0.49). There was no survival difference in patients undergoing primary surgery and non-responders to nCTx (*p* = 0.5) (Figure 5). In the Lauren mixed type patients, there was a trend towards improved survival for responders without statistical significance: the median survival was 103 months in responders vs. 57 months in non-responders (*p* = 0.12) and 31 months in patients undergoing primary surgery (*p* = 0.13). There was no survival difference in patients undergoing primary surgery and non-responders to nCTx (*p* = 0.5) (Figure 6).

**Figure 1.** Survival curves for Lauren intestinal subtype after PSM stratified by surgery only vs. chemotherapy plus surgery.

**Figure 2.** Survival curves for Lauren mixed subtype after PSM stratified by surgery only vs. chemotherapy plus surgery.

**Figure 3.** Survival curves for Lauren diffuse subtype after PSM stratified by surgery only vs. chemotherapy plus surgery.

**Figure 4.** Survival curves for intestinal subtype after PSM differentiated by responders, non-responders, and surgery only.

**Figure 5.** Survival curves for diffuse subtype after PSM differentiated by responders, non- responders and surgery only.

**Figure 6.** Survival curves for mixed subtype after PSM differentiated by responders, non-responders and surgery only.

Recurrence rates and disease free survival were analyzed for the PS-matched groups. In the intestinal type subgroup, the recurrence rates were 79/170 (46.5%) in the surgery only group as compared to 89/170 (52.4%) in the chemotherapy + surgery group (*p* = 0.33). Disease free median survival was 30 months (1–176) in the primary surgery group and 29.5 months (1–242) in the chemotherapy + surgery group (HR 1.12; CI95% 0.83–1.12; *p* = 0.45). In the diffuse type subgroup, the recurrence rates were 62/105 (59%) in the surgery only group compared to 67/105 (63.8%) in the chemotherapy + surgery group (*p* = 0.57). Disease free median survival was 24 months (1–176) in the primary surgery group and 17 months (1–204) in the chemotherapy+surgery group (HR 1.28; CI95% 0.91– 1.81; *p* = 0.16). In the mixed type subgroup, the recurrence rates were 35/56 (62.5%) in the surgery only group when compared to 25/56 (44.6%) in the chemotherapy + surgery group (*p* = 0.09). The disease free median survival was 15.5 months (1–171) in the primary surgery group and 38 months (3–202) in the chemotherapy+surgery group (HR 0.52; CI95% 0.31–0.87; *p* = 0.01).

#### **3. Discussion**

This analysis of a large single center cohort, including 1209 patients, demonstrates an association between the benefit of neoadjuvant chemotherapy and the Lauren subtype. Based on the presented data, only those patients demonstrating the intestinal subtype benefit from the application of neoadjuvant chemotherapy for locally advanced gastric cancer. However, this only holds true for those patients developing histopathologic regression. In contrast, there was no benefit for those patients with diffuse subtype. In the diffuse type group, those patients undergoing neoadjuvant chemotherapy even demonstrated a deterioration of survival when compared to patients who had primary surgery. Patients with Lauren mixed type features revealed a potential benefit, especially those responding to chemotherapy; however, this was not statistically significant. Neoadjuvant/perioperative chemotherapy has become standard of care in Europe and it has become manifest in most of the guidelines for locally advanced gastric and gastroesophageal junction cancers [3,11–13]. However, in recent years, it has become increasingly clear that chemotherapy may not be effective for all patients in the same manner. The overall survival rates still range between 20– 40% after five years [7,11,14,15]. This analysis surprisingly demonstrates that patients having

undergone surgery only revealed survival rates around 40%, and this was improved to over 70% when intestinal subtype tumors demonstrated good histopathologic response. In many studies, the histological subtype was described as an independent factor of survival [15–18], but it also determines the effectiveness of the chemotherapy administered. However, the histological subtypes are so far not sufficiently respected in regard of therapeutic decisions, for which the clinical tumor stage is still the only tool to be applied when multimodal therapies are recommended. This is underlined by the present analysis, in which patients were subjected to neoadjuvant/multimodal chemotherapy without respect to the Lauren subtype. Taking into account that only 49 of 331 patients (15%) demonstrated real benefit from preoperative chemotherapy, it has to be stated that 85% of the patients were treated ineffectively and may even have been harmed by (ineffective) cytotoxic drugs (Figure S5). The Spanish AGAMENON research group already published a correlation between the response to chemotherapy and the Lauren subtype in 2017. They also pointed out that there were no subgroup analyses in the large therapy trials for locally advanced stomach cancer, although there were indications of a link [7]. Further, the AGAMENON study incorporated almost only patients undergoing treatment for metastatic disease, which is not comparable to the present analysis. Another important analysis was the multicentric retrospective FREGAT study, which analyzed a similar cohort [19]. However, the French analysis was related to the impact of signet ring cell differentiation on oncologic outcomes and not exactly to Lauren diffuse types. In the present analysis it was found that there was not a single Lauren diffuse type cancer without signet ring cells. None the less, Lauren diffuse types should not be equalized to signet ring cell differentiation. An international European group proposed a new definition for signet ring cell containing gastric cancer, as this is still a matter of debate between surgeons, oncologists, and pathologists [9]. However, this new consensus is neither ratified nor prospectively analyzed nor evaluated in patients undergoing neoadjuvant/multimodal chemotherapy. Biological and prognostic differences for gastric cancer are difficult to evaluate in studies due to the fact that there are different histological classifications for gastric carcinoma histological phenotypes and there is no uniform classification. This is considerably relevant when new chemotherapeutic regimens (FLOT) are propagated as effective in signet ring cell gastric cancer. The prospective FREGAT study (PRODIGE-19-FFCD1103-ADCI002) is currently the only trial that is going to elucidate whether direct surgery is a potential option for signet ring cell type gastric cancer [20]. Another factor that does not allow for direct comparisons is the issue that there is no broad consensus on which tumor regression classification to use (Becker, Mandard, Cologne, etc.). Certainly, this analysis should be replicated by different centers, applying different tumor regression systems in order to determine whether the Lauren diffuse subtype is a non-responding entity. Therefore, the aim of future studies should be to unify the different histological classifications for gastric cancer in order to further investigate the influence of histology on survival and prognosis.

The limitations of this analysis are certainly the monocentric character of the study, the long observation period during which both surgical and perioperative regimens have changed, different chemotherapy regimens having been used, and the fact that FLOT, as the current standard of care, is still underrepresented in this analysis. Although potential biases inherent to the Lauren type subgroups were possibly corrected by PSM, this method cannot compensate for unconscious and biological biases or those factors not having been determined. More than that, it is critical that the PSM resulted in a relatively small number of patients per group. Therefore, no exact statements can be made about unmatched patients. Another limitation is that the PS-matching did not balance adequately for the UICC stages in the Lauren diffuse type subgroup, so the balance is skewed towards more advanced cases in the nCTx+surgery group, which might limit further conclusions regarding survival prognosis. Further, the generalizability of the present results is certainly restricted, as the practice of neoadjuvant/multimodal chemotherapy is only evident in the Western (mostly European) world and the findings are not transferable to Asian patients, due to ethnicity and, more importantly, due to the fact that preoperative chemotherapy is not a standard of care in countries, such as Korea, Japan, and China.

Molecular markers, including microsatellite instability (MSI-H) and the Cancer Genome Atlas (TCGA) molecular subtypes [21], which could have influenced the results of our study were not assessed and is a limitation of our study. A recently published meta-analysis demonstrated that MSI-H could predict outcomes to neoadjuvant chemotherapy [22]. However, this same meta-analysis revealed that MSI-H comprised a very small proportion (2.4%) of non-intestinal type gastric cancers. In the present analysis the number of patients not responding to chemotherapy in the diffuse type group was markedly higher (>80% for non-intestinal type cancer), which does not explain the influence of MSI-status only. Beyond molecular factors, the amount of chemotherapy administered may have also been a confounding factor. Although most of the patients received neoadjuvant chemotherapy only (94.6%), relatively few patients (5.4%) received the perioperative FLOT/MAGIC regimens (i.e., pre-operative + post-operative). We are unable to determine the influence of post-operative chemotherapy on the outcomes in our study due to incomplete data available about the administration of post-operative chemotherapy. Nevertheless, despite these limitations, the results of our study raise questions regarding the benefit of neoadjuvant/perioperative chemotherapy in diffuse-type gastric cancer. Complete surgical resection remains the only curative option for gastric cancer patients, even if overall survival is markedly shorter for patients with diffuse-type histology as compared to intestinal or mixed type histologies. To the authors' knowledge, except for possibly MSI status, which represents a small proportion of patients, there is no existing biomarker in clinical practice that can adequately predict clinical and histopathologic response to neoadjuvant chemotherapy, and future research on identifying other molecular markers are needed.

The clinical implications of this analysis would be to carefully evaluate the application of neoadjuvant/perioperative chemotherapy in diffuse type patients. It remains speculative as to whether a multimodal treatment concept would be harmful for those patients, but it was demonstrated here that it is not beneficial either. Certainly, R0-surgery remains the only option of curation in these patients, even if the overall survival is markedly shorter than in intestinal or mixed type patients.

#### **4. Materials and Methods**

#### *4.1. Patients*

Data from patients who underwent curative surgery for gastroesophageal cancer at the Surgical Department of TUM School of Medicine from 1987 to 2017 were extracted from a prospectively documented database. The data were obtained from the medical records and then transferred to the institutional databases as soon as the patients were discharged from inpatient hospital care. The inclusion criteria for this analysis were: histologically proven gastroesophageal cancer (Siewert type II/III, all non-cardia cancers) staged cT2-cT4cNany undergoing neoadjuvant/perioperative chemotherapy after multidisciplinary team review, the Lauren histotype confirmed by expert pathologist (intestinal, diffuse or mixed type). The exclusion criteria were: Siewert type I, metastatic disease, hospital mortality within 30 days, loss of follow-up within a 60 months period, macroscopic residual cancer after surgery (R2), and indeterminate Lauren histotypes. Neoadjuvant/perioperative treatment consisted of either preoperative two cycles cisplatin or oxaliplatin/leucovorin/5-FU (PLF/OLF) only or perioperative three cycles of ECX/ECF (MAGIC) or perioperative four cycles FLOT [12,23]. All of the surgical procedures were performed according to the Japanese guidelines for GC treatment, including standardized D2-lymphnode dissection [24]. In the case of GE junction cancer (Siewert type II and III), the surgical procedure was extended to the distal esophagus. All of the patients received intraoperative frozen sections for the oral resection margin in order to confirm R0 resection. If the resection margin was positive, the surgical procedure was extended to the distal esophagus and esophagectomy was carried out whenever necessary. Circumferential and aboral resection margins were not determined intraoperatively on a routine basis. All of the resected specimens

were examined by one or two specialized pathologists, being classified according to the TNM-classification and staged according to UICC-recommendations (8th edition) [25]. The histopathologic response was graded according to the Becker classification. Patients with 0–10% remnant viable tumor cells within the tumor area were graded as histopathologic responders (Becker Ia/Ib), whereas all other patients (Becker II (10–50% remnant viable tumor cells) and Becker III (>50% remnant viable tumor cells)) were graded as histopathologic non-responders [26]. Except for patients receiving FLOT or MAGIC regimens (n = 64, 5.4%, adjuvant chemotherapy was not considered on a routine basis. Following oncologic surgery, all of the patients were followed up every six to twelve months in an outpatient department (Roman Herzog Comprehensive Cancer Center) over the next five years by EGD and CT scans according to the institutional protocol.

Only deceased or surviving patients with a complete follow-up of at least 60 months were included in this analysis. Survival was computed from the day of surgery. The dataset consisted of patients' gender, age, location (upper, middle, lower third), clinical stages (cT2N0, cT1/cT2cN+, cT3/cT4cN0, cT3/cT4N+), number of dissected lymph nodes, postoperative complications (none, Clavien–Dindo Grade I/II and III/IV), pT- (pT1/pT2/pT3/pT4), pN-(pN0/pN1/pN2/pN3), and UICC-stages (UICC-I/-II/-III), grading (G1/2, G3/4), R-status (R0/R1), Lauren subtype (intestinal, diffuse, mixed), and follow-up period with survival status. Institutional Review Board (IRB)-approval for this study was obtained according to local guidelines (IRB Registration: 364/20 S).

#### *4.2. Statistical Analysis*

Descriptive statistics on demographic and clinical tumor characteristics were calculated as the mean ± standard deviation (continuous variables) and frequencies (categorical variables). The survival time was calculated from the day of surgery to death or last follow up date (at least 60 months after surgery for survivors). The Kaplan–Meier method was used in order to estimate the survival probabilities stratified by the application of neoadjuvant/perioperative chemotherapy. The log-rank test was used to compare the estimated survival. Survival prognosticators were analyzed by uni- and multivariate cox regression analyses. The variables that entered into the model were age, tumor location (all locations), all UICC-stages, Lauren intestinal and diffuse subtypes, R-status, grading, and occurrence of postoperative complications. After univariate analysis, all of the variables were entered in the multivariate model. Statistical analyses were performed while using SPSS version 25 (IBM Inc., Ehningen, Germany). PSM was performed with R and the MatchIt Plugin (Version 3.01, Vienna, Austria, URL http://www.R-project.org/). *p*-values of less than 0.05 were considered to be statistically significant. This retrospective analysis was approved by the local IRB (No.364/20s; Ethikkommission der Fakultät für Medizin, TUM School of Medicine).

#### **5. Conclusions**

In conclusion, the present findings demonstrate that the Lauren subtype might be a relevant prognostic factor in relation to overall survival after neoadjuvant/perioperative chemotherapy for locally advanced gastric or gastroesophageal cancer. Data from this analysis suggest that patients with a diffuse subtype may not benefit from neoadjuvant chemotherapy, but further exploration of other factors (e.g., molecular markers, MSI status, EBV-status, etc.), validation in prospective studies, and evaluation of other novel treatments (e.g., immune checkpoint inhibitors) are urgently required.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/2072-669 4/13/2/290/s1, Figure S1: Love plot for propensity-score matching of confounding variables within the respective Lauren type subgroups, Figure S2. Kaplan Meier curve for OS in UICC stage I of PSM-cohort, Figure S3. Kaplan Meier curve for OS in UICC stage II of PSM-cohort, Figure S4. Kaplan Meier curve for OS in UICC stage III of PSM-cohort, Figure S5. From 331 patients only 49 (15%) revealed histopathologic response and thus survival benefit.

**Author Contributions:** Conceptualization: A.N. and D.R.; Methodology: D.R.; Software: D.R.; Validation, R.S., D.R., A.N., J.S.-H., C.O. and H.F.; formal analysis: D.R. and R:S.; investigation: C.O., R.S. and D.R.; Data curation: C.O., R.S. and D.R., writing—original draft preparation: R.S. and D.R., writing—review and editing: R.S., A.N., C.O., J.S.-H., H.F., D.R.; supervision: A.N. and H.F.; project administration D.R.; All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding

**Institutional Review Board Statement:** Institutional Review Board (IRB)-approval for this study was obtained according to local guidelines (IRB Registration: 364/20 S).

**Informed Consent Statement:** Informed consent was not required due to the retrospective nature of this study according to §27 Bayerisches Krankenhausgesetz.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to European data protection regulation.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


### *Review* **Progress in Multimodal Treatment for Advanced Esophageal Squamous Cell Carcinoma: Results of Multi-Institutional Trials Conducted in Japan**

**Kazuo Koyanagi \*, Kohei Kanamori, Yamato Ninomiya, Kentaro Yatabe, Tadashi Higuchi, Miho Yamamoto, Kohei Tajima and Soji Ozawa**

> Department of Gastroenterological Surgery, Tokai University School of Medicine, Isehara 259-1193, Japan; heyhey.cohey@gmail.com (K.K.); yamato.ninomiya@gmail.com (Y.N.); k-yatabe@tokai-u.jp (K.Y.); tadashi.h@tsc.u-tokai.ac.jp (T.H.); miho-n@is.icc.u-tokai.ac.jp (M.Y.); tadidas0203@gmail.com (K.T.); sozawa@tokai.ac.jp (S.O.)

**\*** Correspondence: kkoyanagi@tsc.u-tokai.ac.jp; Tel.: +81-463-93-1121

**Simple Summary:** In Japan, the therapeutic strategies for esophageal squamous cell carcinoma (ESCC) are based on the results of multi-institutional trials conducted by the Japan Esophageal Oncology Group (JEOG), a subgroup of the Japan Clinical Oncology Group (JCOG). Since there are several differences in the factors influencing the treatment approach for esophageal cancer between Eastern and Western countries, the therapeutic strategies adopted in Asian countries, especially Japan, are often different from those in Western countries. Because a transthoracic esophagectomy with three-field lymph node dissection has been performed as a standard surgical procedure for advanced thoracic ESCC in Japan, multimodal treatment for ESCC has been developed to improve the surgical outcomes after this relatively invasive surgical procedure. In this review, we describe the history and current status of therapeutic strategies for ESCC in Japan with a focus on the results of clinical trials conducted by the JEOG.

**Abstract:** In Japan, the therapeutic strategies adopted for esophageal carcinoma are based on the results of multi-institutional trials conducted by the Japan Esophageal Oncology Group (JEOG), a subgroup of the Japan Clinical Oncology Group (JCOG). Owing to the differences in the proportion of patients with squamous cell carcinoma among all patients with esophageal carcinoma, chemotherapeutic drugs available, and surgical procedures employed, the therapeutic strategies adopted in Asian countries, especially Japan, are often different from those in Western countries. The emphasis in respect of postoperative adjuvant therapy for patients with advanced esophageal squamous cell carcinoma (ESCC) shifted from postoperative radiotherapy in the 1980s to postoperative chemotherapy in the 1990s. In the 2000s, the optimal timing of administration of perioperative adjuvant chemotherapy returned from the postoperative adjuvant setting to the preoperative neoadjuvant setting. Recently, the JEOG commenced a three-arm randomized controlled trial of neoadjuvant therapies (cisplatin + 5-fluorouracil (CF) vs. CF + docetaxel (DCF) vs. CF + radiation therapy (41.4 Gy) (CRT)) for localized advanced ESCC, and patient recruitment has been completed. Salvage and conversion surgeries for ESCC have been developed in Japan, and the JEOG has conducted phase I/II trials to confirm the feasibility and safety of such aggressive surgeries. At present, the JEOG is conducting several trials for patients with resectable and unresectable ESCC, according to the tumor stage. Herein, we present a review of the JEOG trials conducted for advanced ESCC.

**Keywords:** esophageal squamous cell carcinoma; multimodal treatment; neoadjuvant chemotherapy; neoadjuvant chemoradiotherapy; definitive chemoradiotherapy

**Citation:** Koyanagi, K.; Kanamori, K.; Ninomiya, Y.; Yatabe, K.; Higuchi, T.; Yamamoto, M.; Tajima, K.; Ozawa, S. Progress in Multimodal Treatment for Advanced Esophageal Squamous Cell Carcinoma: Results of Multi-Institutional Trials Conducted in Japan. *Cancers* **2021**, *13*, 51. https://dx.doi.org/10.3390/ cancers13010051

Received: 26 October 2020 Accepted: 24 December 2020 Published: 27 December 2020

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**Copyright:** © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/ licenses/by/4.0/).

#### **1. Introduction**

Multimodal treatment approaches have led to improved oncological outcomes of patients with esophageal squamous cell carcinoma (ESCC) worldwide [1]. Since there are several differences in the factors influencing the treatment approach for esophageal cancer, such as differences in the proportion of patients with squamous cell carcinoma among all patients with esophageal carcinoma, chemotherapeutic drugs available, and surgical procedures employed, between Eastern and Western countries, the therapeutic strategies adopted in Asian countries, especially Japan, are often different from those in Western countries [2]. In Japan, a transthoracic esophagectomy with cervical, mediastinal, and abdominal (three-field) lymph node dissection has been established and still performed as a standard surgical procedure for advanced thoracic ESCC [3]. Therefore, multimodal treatment for esophageal squamous cell carcinoma has been developed to improve the surgical outcomes after this relatively invasive surgical procedure. On the other hand, in many Western countries, the Ivor Louis esophagectomy is the standard perioperative treatment. In addition to the surgical procedures, the strategy of multimodal treatment for advanced ESCC, such as tumors invading deeper than the muscle layer and/or with regional lymph node metastasis, has evolved differently in Japan and in Western countries.

Considering these characteristics of surgical procedures in Japan, the Japan Esophageal Oncology Group (JEOG), a subgroup of the Japan Clinical Oncology Group (JCOG) has developed the optimal therapeutic strategies for advanced ESCC that were determined by multi-institutional trials [4]. We describe the history and current status of therapeutic strategies for esophageal squamous cell carcinoma in Japan and also the differences to those of Western countries, with a focus on the results of clinical trials conducted by the JEOG.

#### **2. Postoperative and Preoperative Therapies Used for ESCC in Japan**

#### *2.1. History of Postoperative Therapy*

#### 2.1.1. Preoperative and Postoperative Radiotherapy

Preoperative radiation therapy was the predominantly employed postoperative treatment for ESCC in the 1970s. It was generally believed that this approach would improve the resectability of the primary tumor and prevent local tumor recurrence [5]. On the other hand, the superiority of postoperative radiotherapy was highlighted by some research groups, who reported lower postoperative morbidity and improved survival rates, based on a retrospective comparison with a control group [6]. Therefore, the JEOG conducted a randomized controlled trial (RCT) to determine which mode of radiotherapy, preoperative or postoperative radiotherapy, would provide better survival. This study (JCOG 8201, 1981–1983) compared preoperative radiotherapy (30 Gy) plus postoperative radiotherapy (24 Gy) with postoperative radiotherapy (50 Gy) only (Table 1). The results revealed significantly better survival rates in the surgery plus postoperative radiotherapy alone group as compared to that in the surgery plus preoperative radiotherapy plus postoperative radiotherapy group [7]. The results prompted a switch of the timing of administration of postoperative therapy for ESCC from preoperative to postoperative, and there was a general movement away from preoperative radiotherapy to postoperative radiotherapy.


*Cancers* **2021**, *13*, 51

**Table 1.**

Overview of clinical trials of adjuvant therapy for ESCC in Japan.

#### 2.1.2. Postoperative Radiotherapy versus Postoperative Chemotherapy

In Japan, cisplatin has been considered a useful drug for the treatment of esophageal cancer since the early 1980s. The JEOG conducted a RCT to determine whether postoperative radiation therapy or postoperative chemotherapy might provide the better survival rate. This study (JCOG8503, 1984–1987) compared postoperative radiotherapy (50 Gy) with postoperative chemotherapy (cisplatin 70 mg/m2 + vindesine 3 mg/m2 × 2 courses). At the time of this trial, 5-FU was not yet widely available, and the combination of cisplatin plus vindesine, which was the standard treatment for non-small-cell lung cancer at that time, was used in the study. Although the study did not reveal any significant difference in the 5-year overall survival (OS) between the two treatment arms, the results at least suggested that postoperative chemotherapy was not inferior to postoperative radiotherapy, which was the standard of care in the world at the time [8]. Therefore, chemotherapy with cisplatin became generally accepted as the postoperative treatment regimen for ESCC in Japan.

#### 2.1.3. Postoperative Chemotherapy versus Surgery Alone

There have been marked advances in the surgical techniques used for esophageal cancer surgery, especially in regard to lymphadenectomy, including specific resection of the superior mediastinal cervical lymph nodes, which has become a standard procedure in Japan since the late 1980s. Therefore, the JEOG conducted a RCT to investigate whether postoperative chemotherapy could improve the survival in patients undergoing esophagectomy with three-field lymphadenectomy. This study (JCOG 8806, 1988–1991) compared surgery alone with surgery plus postoperative chemotherapy (cisplatin 70 mg/m<sup>2</sup> + vindesine 3 mg/m2 × 2 courses) and revealed no significant difference in the 5-year OS rate between the two groups, so that esophagectomy with three-field lymphadenectomy alone was adopted as the standard of care for ESCC at that time [9].

Thereafter, two phase II trials indicated that CF was superior to combined cisplatin plus vindesine as postoperative therapy for advanced esophageal cancer. Therefore, the JEOG initiated a RCT to determine whether postoperative chemotherapy with CF was additively effective in improving survival as compared to surgery with two- or three-field lymphadenectomy alone for ESCC, pathologic stage II/III, except T4. This trial (JCOG 9204, 1992–1997) compared surgery alone with surgery plus postoperative chemotherapy (80 mg/m<sup>2</sup> cisplatin on day 1 + 800 mg/m2 5-FU on days 1–5 × 2 courses). The primary endpoint of the study was the 5-year disease-free survival (DFS) rate, and the DFS rate in the postoperative chemotherapy group (120 patients) was better than that in the surgeryalone group (122 patients) (55% vs. 45%, *p* = 0.04); the 5-year OS rates were 61% and 52% (*p* = 0.13), respectively. The improved outcomes with postoperative chemotherapy were more pronounced in the subgroup with lymph node metastases [10]. Based on these findings, surgery followed by postoperative CF chemotherapy was considered as the standard of care for advanced ESCC patients in the late 1990s.

#### 2.1.4. Postoperative Chemotherapy versus Preoperative Chemotherapy

While postoperative chemotherapy had been the standard of care for esophageal cancer in Japan, in the West, preoperative chemotherapy had remained the mainstay of treatment due to the high invasiveness of and morbidity associated with surgery [11]. Therefore, it remained controversial as to whether preoperative chemotherapy might have a superior effect on the survival of esophageal cancer patients as compared to surgery alone or surgery plus postoperative chemotherapy. Therefore, the JEOG conducted a RCT to determine the optimal timing of chemotherapy (preoperative vs. postoperative) in patients with locally advanced ESCC. In this study (JCOG9907, 2000–2006), patients with clinical stage II/III ESCC, excluding T4 cases, were randomly assigned to groups that received either preoperative or postoperative chemotherapy (cisplatin 80 mg/m<sup>2</sup> on day 1 and 5-FU 800 mg/m<sup>2</sup> continuous infusion over days 1–5, up to 2 courses with a 3-week interval). The primary endpoint of progression-free survival did not reach the discontinuation boundary, but the OS was better in the preoperative chemotherapy group (164 patients) than in the postoperative chemotherapy group (166 patients) (*p* = 0.01). An updated analysis showed that the 5-year OS rate was 43% in the postoperative chemotherapy group and 55% in the preoperative chemotherapy group (hazard ratio (HR), 0.73, 95% confidence interval (CI), 0.54–0.99, *p* = 0.04) [12]. In addition, preoperative chemotherapy was not associated with an increased risk of postoperative complications or hospital mortality [13].

There were three possible reasons for the favorable results of preoperative chemotherapy in this trial. First, downstaging was achieved with preoperative chemotherapy in some patients. The proportion of patients with clinical stage II was similar in the two groups, but the proportion of patients with pathological stage II or less was higher in the preoperative than in the postoperative chemotherapy group. Second, the frequency of complete resection (R0) was slightly higher in the preoperative chemotherapy group than in the postoperative chemotherapy group. Third, the completion rate of the protocol treatment was much higher in the preoperative chemotherapy group than in the postoperative chemotherapy group; protocol-based treatment with two courses of chemotherapy and R0 resection was completed in 85.4% of patients in the preoperative chemotherapy group, but in only 75.0% of patients of the postoperative chemotherapy group [14]. These results led to preoperative chemotherapy with CF becoming established as the standard of care for patients with stage II/III ESCC in Japan (Figure 1). Thus, the optimal timing of chemotherapy again changed from postoperative chemotherapy to preoperative chemotherapy.

**Figure 1.** Treatment strategies for stage II/III ESCC, adapted and modified from guidelines of the Japan Esophageal Society. ESCC, esophageal squamous cell carcinoma; CRT, chemoradiotherapy.

#### 2.1.5. Postoperative Chemotherapy for ESCC in Western Countries

Reports of postoperative chemotherapy for ESCC were very few. The French Association for Surgical Research performed a randomized controlled trial comparing surgery alone with postoperative chemotherapy using CF for patients with ESSC [15] (Table 2). Before randomization, they separated 120 patients into two groups, curative complete resection and palliative resection leaving residual macroscopic or microscopic tumor tissue. As a result, OS was similar in the two groups, with almost identical medians of 13 months in the postoperative group and 14 months in the surgery-alone group. The survival curves with or without chemotherapy were similar in the curative resection group and also in the palliative resection group. Based on these data, it was concluded that CF followed by surgery is not useful for patients with ESCC.

#### 2.1.6. Preoperative Chemotherapy for ESCC in Western Countries

Ancona and colleagues compared surgery alone with preoperative chemotherapy using CF plus surgery for stage II/III ESCC [16]. The surgical procedure adopted in this study was transthoracic esophagectomy combined with two-field lymphadenectomy. The 5-year OS (primary endpoint) was 22% in the surgery-alone group and 34% in the preoperative chemotherapy group (*p* = 0.55). They concluded that improved long-term survival was obtained in patients with clinically resectable ESCC who underwent preoperative

chemotherapy and obtained a pathologic complete response. They also emphasized the necessity of major efforts to identify patients who are likely to respond to preoperative chemotherapy.

Two pivotal RCTs in terms of preoperative chemotherapy are known worldwide, the Radiation Therapy Oncology Group (RTOG) and the Medical Research Council (MRC) trials, although both squamous cell carcinoma and adenocarcinoma were included. The RTOG trial compared surgery alone with preoperative chemotherapy using CF plus surgery followed by two courses of postoperative chemotherapy in operable esophageal cancer cases [17]. More than 50% of patients (53% in the surgery-alone group and 54% in the preoperative chemotherapy group) consisted of adenocarcinoma, and both transthoracic and transhiatal esophagectomy were performed as the surgical procedures without limiting the extent of lymphadenectomy. The median survival was 16.1 months in the surgery-alone group and 14.9 months in the preoperative chemotherapy group (*p* = 0.53). There were no differences in survival between patients with squamous cell carcinoma and those with adenocarcinoma. They concluded that preoperative chemotherapy with a combination of CF did not improve OS among patients with squamous cell carcinoma or adenocarcinoma. They reported, in a long-term update, that the median survival times were 1.3 years for patients receiving preoperative chemotherapy versus 1.3 years for those undergoing surgery alone [18]. They described similar outcomes to those described by other researchers, with objective response to preoperative chemotherapy being associated with better survival. Investigators in the Medical Research Council Oesophageal Cancer Working Party compared surgery alone with preoperative chemotherapy using CF plus surgery for resectable esophageal cancer [19]. Two-thirds of patients (67% in the surgery-alone group and 66% in the preoperative chemotherapy group) consisted of adenocarcinoma, and the surgical procedure was chosen by the operating surgeon. The median survival was 13.3 months in the surgery-alone group and 16.8 months in the preoperative chemotherapy group (*p* = 0.004), and the 2-year survival rates were 34% and 43%, respectively. Hazard ratios for treatment effect in patients with squamous cell carcinoma and those with adenocarcinoma were the same, showing that the effects of treatment were extremely similar for both histologic types. They concluded that preoperative chemotherapy improved survival in patients with resectable esophageal cancer. In long-term update results of this trial, they reported that the 5-year survival was 17.1% in the surgery-alone group and 23.0% in the preoperative chemotherapy group, with consistent treatment effect achieved in both histologic types [20]. They emphasized that preoperative chemotherapy is an essential standard of care for patients with resectable esophageal cancer. Because two pivotal studies demonstrated completely different conclusions, the benefit of preoperative chemotherapy, even when limited to patients with ESCC was controversial, and there seems to be no current worldwide consensus as to the optimal preoperative chemotherapy.

#### 2.1.7. Preoperative Chemoradiotherapy for ESCC in Western Countries

A Dutch group (Chemoradiotherapy for Oesophageal Cancer Followed by Surgery Study (CROSS) Group) compared surgery alone with preoperative chemoradiotherapy followed by surgery for potentially curable squamous cell carcinoma (23%) or adenocarcinoma (75%) of the esophagus or the esophagogastric junction. A transthoracic esophagectomy with two-field lymphadenectomy was performed. A transhiatal resection was preferred for the tumors involving the esophagogastric junction. The median survival was 48.6 months in the preoperative chemoradiotherapy group and 24.0 months in the surgery-alone group (*p* = 0.003), and 81.6 months and 21.1 months, respectively, for patients with squamous cell carcinoma. The 5-year OS was 47% and 33%, respectively. They concluded that preoperative chemoradiotherapy improved survival among patients with potentially curable esophageal or esophagogastric junction cancer, regardless of histologic subtype [21]. The result of this study supported preoperative chemoradiotherapy as a standard of care for locally advanced esophageal cancer in Western countries in which adenocarcinoma is predominant histologic type.

The most recent meta-analysis by Sjoquist et al. [22] included 12 RCTs comparing preoperative chemoradiotherapy vs. surgery alone, with a total of 1854 patients. A significant survival benefit was evident for preoperative chemoradiotherapy with an HR of 0.78 (0.70–0.88; *p* < 0.0001). In a subgroup analysis, the HR for squamous cell carcinoma was 0.80 (0.68–0.93; *p* = 0.004) and for adenocarcinoma it was 0.75 (0.59–0.95; *p* = 0.02). This updated meta-analysis provided stronger evidence for a survival benefit than the former meta-analysis conducted by the same group [23]. This analysis also compared preoperative chemotherapy to preoperative chemoradiotherapy and demonstrated a non-statistically significant survival benefit for preoperative chemoradiotherapy (HR 0.88, 0.76–1.01; *p* = 0.07). Therefore, controversy still exists as to whether preoperative chemotherapy or preoperative chemoradiotherapy is more beneficial [24]. A RCT comparing preoperative chemotherapy using CF (91 patients including 25 SCC patients) with preoperative chemoradiotherapy (90 patients including 25 SCC patients) was conducted in Sweden and Norway. They revealed that the addition of radiotherapy to preoperative chemotherapy resulted in higher pathological complete response (pCR) rate and higher R0 resection rate, without significantly affecting survival [25].

#### *2.2. Future Candidates for Preoperative Therapy for ESCC*

#### 2.2.1. Adequate Preoperative Therapy

The results of a subgroup analysis in the JCOG9907 study showed that preoperative chemotherapy was more effective in clinical stage II or T1–2 esophageal cancer patients than in stage III or T3 patients, i.e., in patients with relatively early-stage disease. Furthermore, the low single-site recurrence rates of 31% and 25% in cases of tumor recurrence in the two groups could be attributable to our elaborate surgical technique. The results of this study suggested that preoperative chemotherapy with cisplatin plus 5-FU would be a good treatment strategy when aggressive surgery provides adequate local tumor control, but when the local tumor control is inadequate, more aggressive adjuvant therapy, such as more intensive preoperative chemotherapy or preoperative chemoradiotherapy, may be the preferable treatment strategy to obtain adequate local tumor control as well as systemic disease control. Docetaxel is one of the most promising agents for esophageal cancer, and an exploratory study of preoperative chemotherapy with DCF for locally advanced ESCC showed a favorable response rate (61.5%), with no treatment-related deaths. The therapeutic promise of docetaxel was demonstrated in a randomized phase II trial [26]. However, the clinical question of whether preoperative chemotherapy or preoperative chemoradiotherapy is superior still remained unresolved.

Under this circumstance, the JEOG initiated a three-arm randomized controlled trial (JCOG1109) in 2012, to confirm the superiority of DCF and chemoradiotherapy with CF (CF-RT) over CF as preoperative therapy for locally advanced ESCC in terms of the OS [27]. Patients in group A were treated with two courses of preoperative CF (cisplatin 80 mg/m<sup>2</sup> on day 1, 5-FU 800 mg/m2 on days 1–5) repeated every three weeks; group B received three courses of preoperative DCF (70 mg/m<sup>2</sup> docetaxel on day 1, 70 mg/m<sup>2</sup> cisplatin on day 1, 750 mg/m<sup>2</sup> 5-FU on days 1–5) repeated every three weeks; group C received two courses of preoperative chemoradiation (41.4 Gy/23 fractions) with two courses of CF (75 mg/m<sup>2</sup> cisplatin on day 1 plus 5-FU 1000 mg/m<sup>2</sup> on days 1–4) repeated every four weeks. Both transthoracic open esophagectomy and minimally invasive esophagectomy were acceptable in all three groups, and surgery should be performed within 56 days after completion of the preoperative treatment. Patient enrollment was completed in 2018 and follow-up of the enrolled patients is ongoing.



*Cancers* **2021**, *13*, 51

#### 2.2.2. Preoperative Therapy with Immune Checkpoint Inhibitors

Nivolumab and pembrolizumab are immune checkpoint inhibitors, newly developed drugs with antitumor activity. Until recently, no molecular-targeted drugs were approved for the treatment of advanced esophageal cancer, but in 2019, the FDA approved pembrolizumab as a second- or subsequent-line treatment for PD-L1-positive cases [28]. Strong PD-L1 expression is generally observed in esophageal cancers, with reported expression levels in the tumor cells of 15–83% and in immune cells of 13–31% [28–31]. Furthermore, in 2019, an international phase III trial (ATTRACTION-3) showed that nivolumab significantly prolonged the OS in patients with unresectable advanced or recurrent esophageal cancer who were refractory or intolerant to fluoropyrimidine and platinum as compared to the existing taxanes in an international phase III trial [32]. Thus, in Japan, nivolumab was approved in 2020 for use as second-line chemotherapy for patients with unresectable advanced or recurrent esophageal cancer. Based on these results, the JEOG has initiated a phase I trial (JCOG1804E) to evaluate the efficacy of preoperative chemotherapy with the addition of nivolumab to CF and DCF [33].

#### **3. Surgery for ESCC in Japan**

#### *3.1. Techniques of Esohagectomy in Japan*

#### 3.1.1. Approach to Esophagectomy

Open thoracic and abdominal surgery remained the only surgical strategies adopted for esophageal cancer, before Cuschieri first reported thoracoscopic esophagectomy in 1992 [34]. Since then, thoracoscopic/laparoscopic surgery has been developed rapidly and is now considered as a less-invasive approach than open surgery. To date, several thoracoscopic or laparoscopic approaches for resection of thoracic esophageal cancer have come to be defined as minimally invasive esophagectomy (MIE), based on the tumor location, clinical stage, and patient demographics [35,36]. Although, total thoracoscopic esophagectomy and laparoscopic esophagectomy are representative of (total) MIE in a narrow sense, video-assisted thoracoscopic surgery (VATS) [37], esophagectomy with mini thoracotomy (up to an approximately 5-cm incision) in a wider sense, and laparoscopic approaches are also considered as falling within the scope of MIE [38]. In Japan, Akaishi et al. were the first to report the use of thoracoscopic total esophagectomy with en bloc mediastinal lymphadenectomy in 1996 [39]. After these exploratory studies, the number of MIEs performed has increased and there have been advances towards the standardization of surgical techniques.

We reviewed studies that compared the surgical outcomes of open transthoracic esophagectomy (OE) and MIE and found that MIE was not inferior to OE in terms of the accuracy of lymph node dissection and surgical invasiveness, and might also be associated with a reduced risk of respiratory complications [40].

Robot-assisted MIE (RAMIE) was first described in 2004 by Kernstine et al. [41]. In 2006, they published an account of their first experience with the use of RAMIE in combination with conventional laparoscopic surgery and showed that this new surgical procedure is technically feasible and associated with lower blood loss [42].

The da Vinci Robotic Systems (Intuitive, Sunnyvale, CA, USA) provides a threedimensional magnified view of the surgical field [43]. Because of the theoretical advantages of robot-assisted surgery, including articulation of the instruments, tremor filtering, features allowing minimization of large movements for the surgeon, and better ergonomics, it has the potential to accelerate the MIE learning curve. The increased degree of freedom provided by the articulation of the surgical instruments might overcome the movement restrictions caused by the rib cage and improve the accuracy of lymph node dissection around the recurrent laryngeal nerves [44], which could be expected to lead to better outcomes and avoidance of recurrent laryngeal paralysis. Although RAMIE is spreading rapidly in Japan based on these theoretical advantages, there are still several issues to be investigated—the expensive cost of da Vinci Robotic Systems and the clinical usefulness compared with thoracoscopic surgery.

#### 3.1.2. Three-Field Lymph Nodes Dissection

The importance of lymphadenectomy in esophageal cancer surgery has been well established around the world. Ever since Torek reported the first case of successful esophagectomy in 1913 [45], the safety and efficacy of esophagectomy for esophageal cancer have been reported by numerous researchers, and the range of lymph node (LN) dissection has been extended. Three-field LN dissection (3FD) was initiated by two Japanese Surgeons. Kajitani was the first to perform systematic dissection of the LNs around the recurrent laryngeal nerves and developed upper mediastinal LN dissection [46]. Sannohe then reported cervical LN dissection and the incidence of metastases in patients who underwent 3FD [47]. Following these reports, the safety and survival rates of 3FD were also shown by a number of reports in Japan [48–51]. Initially, surgical procedures were performed without considering recurrent laryngeal nerves, and recurrent laryngeal nerve paralysis occurred in many patients. However, with the improvement in surgical technique around recurrent laryngeal nerves, the frequency of recurrent laryngeal nerve paralysis had gradually decreased. In the 1990's, 3FD was accepted worldwide and its safety was established [52–54]. Kato et al. reported that patients with esophageal cancer who underwent 3FD showed better OS rates than those who received 2FD [55]. Igaki et al. showed that neck dissection is also important in patients with lower thoracic ESCC. They reported that 3FD for patients with LN metastases in the upper and/or central mediastinum can improve the survival rate as compared to 2FD, even in patients with lower thoracic ESCC [3]. Moreover, Altorki et al. reported 80 patients who underwent esophagectomy with 3FD, in 30% of whom the disease was upstaged following 3FD [52]. Based on these previous reports, esophagectomy with 3FD is currently adopted as the standard procedure for thoracic esophageal cancer in Japan.

We speculate the following reasons for the prolonged postoperative survival associated with 3FD. First, extended LN dissections may increase the curative potential of esophagectomy. Esophageal cancer can cause LN metastasis extending from the cervical to the abdominal fields, and an extended range of LN dissection could be expected to lead to better elimination of tumor cells. Second, extended LN dissection improves the accuracy of staging and leads to better postoperative survival in patients with each disease stage. Even if an upper mediastinal LN dissection could be performed with both 3FD and 2FD, the number of dissected LNs in the upper mediastinum would be higher in 3FD, because of the added cervical approach in 3FD. Therefore, 3FD may be beneficial for obtaining better postoperative survival.

Recently, several systematic reviews and meta-analyses have been reported. Shang et al. analyzed the long-term survival of the patients and showed that 3FD was superior to 2FD in patients with LN metastasis in the cervical or upper mediastinal LNs [56]. Ma et al. also conducted a meta-analysis and reported that 3FD was associated with improved survival rates following esophagectomy [57].

#### *3.2. Salvage and Conversion Surgery*

#### 3.2.1. Terminology

Salvage surgery is generally considered as a surgical procedure for radical resection of a lesion that has failed to resolve, or that has resurfaced after radiation and/or chemotherapy, with the intent of cure. Conversion surgery, on the other hand, is considered to be a procedure that involves a change in treatment, such as from chemotherapy and/or radiation to surgical resection. The concept of induction chemotherapy, especially for patients with borderline resectable esophageal cancer, which involves deciding whether to perform conversion surgery or chemoradiotherapy after chemotherapy, has also been becoming popular recently, and clinical trials are under way in Japan. As described below, chemoradiation therapy for unresectable advanced esophageal cancer is also widely used. Salvage surgery and conversion surgery are playing increasingly important roles in the multimodal treatment of advanced esophageal cancer (Figure 2).

**Figure 2.** Treatment strategies for stage IVa ESCC, adapted and modified from guidelines of the Japan Esophageal Society. ESCC, esophageal squamous cell carcinoma; CRT, chemoradiotherapy; CT, chemotherapy; CR complete response.

#### 3.2.2. Clinical Trials for Resectable ESCC

In 1999, a phase III trial conducted in the US in patients with T1-3N0-1M0 ESCC showed that CRT with CF concurrently with 50.4 Gy radiation yielded a significantly improved 5-year OS of 26%, as compared to 0% for radiation alone [58]. This made CRT a standard noninvasive treatment for patients who did not wish to undergo surgery. Therefore, the JEOG conducted a phase II study (JCOG9906, 2000–2002) to evaluate the efficacy and safety of CRT in patients with Stage II/III ESCC (Table 3). CRT was performed in 96 patients and the outcomes in the CRT arm were comparable to those in the preoperative chemotherapy plus surgery arm, and the toxicity was manageable. However, late toxicities, comprising Grade 3/4 esophagitis (13%), pericardial (16%) and pleural (9%) effusion, and radiation pneumonitis (4%), were observed, causing four deaths, and it was concluded that further improvement was required for reduction in the incidence of late toxicities [59].

In Japan, based on the results of trials, definitive CRT (dCRT) with 60 Gy of radiation in combination with CF therapy is adopted for patients with Stage II/III ESCC who do not wish to undergo surgery. However, the high incidence of late toxicities and of complications after salvage surgery have made dCRT for Stage II/III ESCC an option that could be considered. For this reason, the JEOG conducted a single-arm confirmatory study (JCOG 0909, 2010–2014) to evaluate the reduction in the incidence of late toxicities with a reduced radiation dose to 50.4 Gy, the improvement in the outcomes with the inclusion of salvage therapy, and the safety of salvage therapy. The 3-year OS rate was 74.2% (90% CI: 65.9–80.8), which was higher than the expected rate of 55%. Salvage surgery resulted in Grade 3/4 postoperative mobility in five patients (20%) and postoperative death in one patient (4%), but R0 surgery was possible in 76% of cases [60]. Salvage surgery was considered as an effective treatment option for limited indications, and CRT, consisting of radiotherapy at 50.4 Gy plus CF, became the standard of care for esophageal cancer patients in Japan who preferred nonsurgical treatment.

#### 3.2.3. Clinical Trials for Unresectable ESCC

The JEOG conducted a phase II/III trial (JCOG0303, 2004–2009) of CRT for esophageal cancer patients with T4b disease or unresectable lymph nodes with standard-dose CF (Arm A) versus low-dose CF (Arm B). Because there were no differences in the toxicities between the two arms, Arm B was judged as not worthy of further evaluation in the phase III setting and the study was terminated [61]. Daily RT plus low-dose CF chemotherapy did not qualify for further evaluation as a new treatment option for patients with locally advanced unresectable esophageal cancer.


122

therapy with docetaxel, cisplatin, and

5-fulorouracil;

 CS, conversion surgery; † UICC at the time; \* median, month.

In 2013, a multicenter phase II trial (COSMOS trial) was performed to assess the safety and efficacy of induction DCF chemotherapy and subsequent conversion surgery for initially unresectable locally advanced ESCC. Conversion surgery was performed in 41.7% of patients after induction chemotherapy or subsequent CRT, and R0 resection was achieved in 95% of these patients, with no serious postoperative complications. Induction DCF chemotherapy followed by conversion surgery as a multidisciplinary treatment strategy showed promise in terms of both the tolerability and efficacy in patients with locally advanced unresectable ESCC [62]. Based on these results, the JEOG designed a phase III trial (JCOG1510) to determine the outcomes of conversion surgery after induction chemotherapy [63]. The purpose of this study was to confirm the superiority, in terms of the OS, of induction chemotherapy with DCF followed by conversion surgery or dCRT over dCRT alone OS in patients with locally advanced unresectable ESCC, and patient enrollment is ongoing.

#### **4. Discussion**

In this review, we have shown the history and results of RCTs for advanced ESCC in Japan and also presented ongoing RCT conducted by JEOG. Thanks to the JEOG's continued efforts, we have been able to achieve better outcomes for advanced ESCC. Rationale for multimodal treatment for advanced ESCC in Japan is different from other Western countries—multimodal treatment for ESCC has been shown to improve the outcomes after surgical treatment. Non-surgical treatment has not been considered as standard treatment, therefore, RCT that compared the superiority or non-inferiority of non-surgical treatment over the esophagectomy has not been conducted. There are two possible reasons for this. One is that the prognosis of the patients was dramatically improved after introduction of three-field lymph node dissection. The other is that few drugs have been approved by national insurance and used for ESCC in Japan. In addition to cisplatin and 5-FU, until 2019, only docetaxel and paclitaxel could be used. In 2020, nivolumab was approved and is now available for unresectable and/or recurrent ESCC. Given these backgrounds, we believe that new perspectives should be considered for multimodal treatment of advanced ESCC. Quality of life (QOL) is considered as an important issue. Although three-field lymph node dissection could contribute the better prognosis, this kind of invasive procedure might reduce the patient's QOL. We also need to investigate new drugs that can be used for ESCC.

Identification of responders and non-responders for chemotherapy and radiotherapy is an urgent need based on the evidence that histological complete response is predictive of long overall survival. If it were possible to predict responders and non-responders, unnecessary toxicity, and time caused by unnecessary preoperative chemotherapy or chemoradiotherapy, could be avoided. Therefore, future RCT should focus on the identification of prognostic and predictive biomarkers as well as the integration of molecular targets. Clinical trials incorporating molecularly targeted therapeutics into multimodal treatment for esophageal cancer are being initiated. Although promising results have not been demonstrated yet, development of molecularly targeted drugs could contribute the progress of multimodal treatment for advanced ESCC.

Immune checkpoint inhibitors are already available in ESCC and are another promising candidate for multimodal treatment because strong PD-L1 expression is generally observed in esophageal cancers, with reported expression levels in the tumor cells of 15–83% and in immune cells of 13–31% [28–31]. Furthermore, in 2019, an international phase III trial (ATTRACTION-3) showed that nivolumab significantly prolonged the OS in patients with unresectable advanced or recurrent esophageal cancer who were refractory or intolerant to fluoropyrimidine and platinum as compared to the existing taxanes in an international phase III trial [32]. Immune checkpoint inhibitors have a different mechanism of action in cancer tissues to that of traditional anticancer drugs. Thus, nivolumab as well as well as pembrolizumab are expected to be studied as very promising candidates for multimodal treatment for advanced ESCC.

#### **5. Conclusions**

We have summarized the history and current status of multidisciplinary treatment for ESCC in Japan, mainly based on the results of clinical trials conducted by the JEOG. We are expecting the results of a three-arm randomized controlled trial of preoperative chemotherapy (JCOG1109) and a phase I trial (JCOG1804E) to evaluate the efficacy of adding nivolumab to preoperative CF and DCF.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are openly available.

**Conflicts of Interest:** The authors declare no conflict of interest.

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