*4.4. Immune Checkpoint Inhibitors Combined with Anti-VEGFR Agents*

Recently, Finn et al. tested the combination of atezolizumab, a monoclonal antibody targeting PD-L1, plus bevacizumab, an anti-VEGF monoclonal antibody, as a front-line treatment of advanced HCC. The trial (IMbrave-150) showed a clear superiority of the dual therapy over sorafenib [15]. The intention-to-treat population included 336 patients in the atezolizumab plus bevacizumab group and 165 patients in the sorafenib group. At the time of the primary interim analysis, the HR for death with atezolizumab plus bevacizumab as compared with sorafenib was 0.58 (95%CI, 0.42–0.79; *p* < 0.001). The reported 12-month OS was 67.2% (95%CI, 61.3–73.1) with atezolizumab plus bevacizumab versus 54.6% (95%CI, 45.2–64.0) with sorafenib. Median PFS was 6.8 months (95%CI, 5.7 to 8.3) and 4.3 months (95%CI, 4.0–5.6) in the respective groups (HR for disease progression or death: 0.59; 95%CI, 0.47–0.76; *p* < 0.001) [15]. Hypertension, proteinuria, and fatigue were the top three treatment-related AEs in the combination arm. Upper gastrointestinal bleeding, a known AE of bevacizumab and a main concern in patients with cirrhosis, occurred in 7% of patients in this group, which is well within the range of previous studies evaluating the use of bevacizumab in HCC [49,50]. Esophageal varices hemorrhage occurred in 2.4% of cases, but only 1.8% were grade ≥3 and less than 1% of cases needed treatment discontinuation. Of note, in this study, causality was reported only in <1% of patients [15]. In this respect, it is important to emphasize that patients intended to receive the combination of atezolizumab plus bevacizumab had undergone endoscopic variceal screening, as per the study protocol. Given the increased bleeding risk associated with bevacizumab, patients with gastro-esophageal varices at risk of bleeding received adequate prophylactic treatment, as must be done in standard care of cirrhotic patients with esophageal varices [51,52]. Increases in aminotransferases and pruritus were other common AEs attributable to atezolizumab but, again, only a few patients (0.6% of cases) needed to stop treatment and developed immune-mediated liver damage. The proportion of patients who discontinued any treatment component because of AEs was 15.5% in the atezolizumab plus bevacizumab group (7% discontinued both components) and 10.3% in the sorafenib group [15]. Overall, AEs leading to dose modification or interruption occurred in 49.5% of patients who received atezolizumab plus bevacizumab and in 60.9% of those who received sorafenib. Therefore, this study provided the first and strong—evidence of the benefit provided by combining an ICI and a VEGFR inhibitor for patients with advanced HCC, and its superiority over sorafenib has undoubtedly already changed the standard of care for these patients, where it has substituted sorafenib as first-line treatment in most cases. Nevertheless, as only patients with Child–Pugh class A were included in this study, which is standard practice in HCC trials, so no consistent data are available regarding efficacy and safety of this combination in patients with a greater impairment in liver function. To date, only one study has reported the outcomes for four Child–Pugh class B patients treated with atezolizumab plus bevacizumab in a Japanese cohort of patients [53]. Among these patients, all patients could be treated without the development of severe AEs until tumor progression and efficacy was comparable to that of Child–Pugh class A patients. These results are undoubtedly important, but further research in larger cohorts of patients is needed before a recommendation can be made for the use of this immunotherapy in patients with Child–Pugh class B liver function. However, we could argue that well selected patients

with Child–Pugh class B7 liver function may be treated safely with atezolizumab plus bevacizumab but close monitoring of biochemistry and close clinical monitoring should be performed and patients should be informed that the benefit of this treatment in the Child–Pugh class B population still has to be determined.

The role of sorafenib and that of lenvatinib and, more in general, the treatment algorithms for the systemic treatment of HCC, will soon need to be reviewed in order to be optimized. Whether TKIs are going to be part of the second-line treatment alternatives, alone or in combination with other agents, is still unknown and extensive research is ongoing to try to adequately frame treatment sequences.

#### *4.5. Immune Checkpoint Inhibitors Combined with Locoregional Treatments for HCC*

To date, no systemic treatment tested in combination with locoregional treatments for HCC has demonstrated benefit in terms of OS. Conversely, ICIs might revolutionize the therapeutic panorama of early and intermediate stage HCC, thus achieving a role not only in the setting of palliative treatment, but also in the curative one. The rationale for their use in combination with radiofrequency ablation (RFA) and TACE relies on the fact that ablative and intra-arterial techniques indirectly induce a peripheral immune response that can enhance the effect of ICIs [54,55] (Figure 2). Namely, the RFA- and TACE-induced necrosis of tumor cells favors the release of tumor antigens and the activation of immune-mediated death of tumor cells, which, in turn, stimulate a peripheral systemic immune response that can potentially be amplified by immune checkpoint blockade [56–61]. Arayu et al. showed that alpha-fetoprotein-specific CD4+ T-cell responses to three immune-dominant epitopes in HCC patients were significantly expanded during and after embolization (*p* < 0.002). Specifically, the development of alpha-fetoprotein-specific CD4+ T-cells after treatment was significantly associated with the induction of >50% necrosis of tumor and an improved clinical outcome (*p* < 0.007) [57]. Similarly, Mizokushiet al, evaluating T-cell responses in patients with HCC undergoing RFA, observed immune responses to antigens for which no T-cell response was detected before RFA [60]. Interestingly, the number of tumor-specific T-cells after RFA correlated with the prevention of HCC recurrence in patients treated with curative intent [60]. Moreover, RFA ablation not only provides activating signals for T-cell responses against HCC, but also augments the pool of circulating natural killer (NK) lymphocytes and enhances preferential expression of NK cells' activating receptors and NK cells' cytotoxicity, and all these effects are seen as soon as one week after treatment [61].

Although very limited data exist in patients with very early or early HCC (BCLC 0 or BCLC A stage) and intermediate HCC (BCLC B stage) treated with ICIs in the adjuvant and neo-adjuvant setting, preliminary data are promising. With regards to the neo-adjuvant setting, a recent pilot randomized, Phase II trial showed that dual treatment with nivolumab plus ipilimumab prior to surgery leads to a complete pathological response rate in 33.3% of cases [62]. An increase in T-cell infiltration and upregulation of cytotoxic and effector memory cell markers in tissue after treatment was also seen, as compared with before treatment [62]. Two other small studies investigated tumor-specific immune responses after combined TACE and RFA treatment, or after each individual treatment, confirming that ablative therapies induce tumor-specific T-cell responses in individual patients upon ablative therapies [59,63].

Combined ICIs plus TACE or RFA are not the only treatments under investigation, as some reports regarding the combination of trans-arterial Y90-radioembolization (TARE) and immune checkpoint blockade have been presented at recent oncological meetings with promising results. In particular, Tai et al. reported the results of a Phase II, open-label, single-center, non-randomized trial regarding the effects of a combined therapy with TARE and nivolumab for advanced HCC in an Asian cohort. Their results showed that this combination had a synergistic effect, with an ORR of 30.5% and with good safety and tolerability profiles [64].

**Figure 2.** Locoregional treatments applied to hepatocellular carcinoma (HCC) induce immunological effects in the tumor microenvironment, which can be amplified by immune checkpoint inhibitors. After radiofrequency ablation (RFA) or trans-arterial chemo-embolization (TACE) or radio-embolization (TARE), necrosis of tumor cells induces increased tumorantigen release, thus facilitating the recruitment and activation of cytotoxic T-cells and dendritic cells. These effects can be exploited by administering immune checkpoint inhibitors (ICIs) to transform an immunosuppressive microenvironment in an immune-supportive one, in which systemic therapies might be more effective.

> Based on these findings, several trials are ongoing to test the efficacy of combined ICIs and locoregional treatments in HCC. This strategy might significantly decrease recurrence rates after treatment with ablative techniques, thus ameliorating long-term prognosis of patients with very early/early HCC. Similarly, ICIs may potentially enhance responses after trans-arterial treatments; this implicates that patients with intermediate stage HCC may be effectively down-staged and might therefore become qualified for curative treatments. Hence, if ongoing studies in this field obtain good results in terms of safety and efficacy, ICIs would not only play a role in the setting of advanced HCC, but would also become a fundamental component of the management of the earlier stages of this tumor.
