1. Introduction
As life expectancy in the Nordic countries increases [
1], we face an increasingly aging population. In Finland, colorectal cancer (CRC) is the second most common cancer, with 3685 new cases reported in 2021 [
2]. The incidence of CRC increases with age, and as the proportion of elderly in the population has increased, so, too, has the incidence of CRC in the population [
3].
The existing excess mortality among elderly CRC patients primarily stems from death due to causes other than CRC, as found in a Dutch study consisting of 9397 patients [
4]. When survival data were corrected for expected death from other causes, no differences between age groups emerged. According to a registry study in the United States among 24,426 colon cancer patients, an older age associated with a lower proportion of colon cancer deaths and a higher proportion of deaths due to cardiovascular disease [
5].
Among elderly CRC patients undergoing surgery, the first year of recovery is particularly important given the high morbidity observed [
6]. However, after surviving the first year postoperatively, survival is comparable to that among younger age groups [
7]. Morbidity postoperatively can be minimized through the evaluation and optimization of patients, especially among older patients [
8].
Yet, only a few previous population-based studies have examined CRC stage-dependent survival among elderly patients. In the past, research into survival among older CRC patients has, to our knowledge, focused more on general survival and not on stage-specific survival. Previous studies have also primarily examined right-sided versus left-sided colon cancer [
9]. With populations growing older, further exploring survival at different stages of CRC is of interest, specifically in elderly populations. Thus, this nationwide population-based registry study aimed to explore elderly CRC patients’ short- and long-term overall survival (OS) based on tumor spread, tumor location, and patient age groups, as well as disease-specific survival (DSS).
4. Discussion
This study, consisting of 11,306 Finnish CRC patients ≥ 75 years old diagnosed between 2006 and 2015, shows that the five-year OS and DSS among elderly patients with CRC is fairly good. In particular, patients aged 75–79 and 80–84 with localized and locally advanced disease experienced a relatively good long-term OS. Furthermore, we observed a similar DSS among patients < 75 years and ≥75 years, particularly among patients with localized disease.
Our results demonstrate that the five-year OS among elderly patients is clearly worse compared with the five-year DSS. Patients with localized disease aged 75–79 had an OS exceeding 70% and those aged 80–84 had an OS of over 50%, whereas the respective DSS is remarkably better (over 90% and 80%). A similar pattern among elderly CRC patients was noted in a recent study based on the SEER database [
12]. That study demonstrated that elderly patients undergoing surgery usually have a better OS and DSS than those receiving palliative treatment alone. This trend was also observed in a recent study among 1482 patients from 2005–2020, which revealed a larger influence of age on OS compared with cancer-specific survival [
13]. These findings emphasize the influence of age on OS and the importance of taking OS into account in treatment decisions. Given that almost half of the elderly patients with localized disease passed away within five years of diagnosis (five-year OS 56.7%, 95% CI 54.3–59.1), treatment decisions must acknowledge that these patients may have a relatively short life expectancy despite surviving CRC.
Contrary to young patients, OS among elderly patients appeared worse in patients with more distal gastrointestinal tumors (
Table 4). According to our results, elderly patients with right-sided colon cancer in general exhibited a better long-term OS than those with left-sided colon cancer or rectal cancer. Our findings differ from earlier studies, suggesting that elderly patients with left-sided colon cancer have a better OS than patients with right-sided disease [
14,
15,
16]. Yet, such reports have included younger patients, which likely affected the results since younger patients usually present with more distal disease [
17]. A recent study among 91,416 patients suggested that those with right-sided colon cancer exhibited a worse OS than patients with left-sided colon cancer; yet, after propensity score matching, the results agreed with our findings, since survival (both overall and disease-specific) was better in patients with right-sided colon cancer compared with left-sided disease [
18]. Elderly CRC patients in our dataset were also more often female. Earlier studies reported a lower mortality and incidence of CRC among women than among men in younger age groups [
19,
20]. Based on these results, it seems that CRC in women emerges at a later age. In our study, the differences in OS between right-sided and left-sided colon cancer became more obvious among patients aged 80–84 and older, after which right-sided colon cancer patients exhibited better survival.
Rectal cancer patients with locally advanced disease had, according to a recent retrospective study from 2004–2018 among 328 patients, a similar DSS to that among younger age groups [
21]. These results differ from ours, since elderly patients with locally advanced disease in which the tumor invaded adjacent tissues (FCR 5) had a worse five-year DSS and OS than that observed among younger patients. Although survival is worse than that among younger patients, the five-year DSS continues to exceed 60% for all age groups. Our patients with locally advanced disease had an OS over 40% up to age 89. The poorer survival among rectal cancer patients may be explained by aggressive rectal cancer care, including extensive surgeries, which are taxing to the elderly already burdened by comorbidities [
22,
23]. The number of emergency surgeries among older CRC patients remains higher than that among younger patients, as demonstrated by a population-based study [
24]. The authors of that study suggested that because older patients more rarely undergo surgery and more often present with tumor-related bowel obstruction, they, therefore, more often require emergency surgery. This is supported by another national cohort study among 31,665 patients, in which 17% of patients > 75 years old presented with bowel obstructions at diagnosis compared with 11% of younger patients [
25]. In the same study, patients > 75 years old received adjuvant (15% vs. 29%) and palliative (48% vs. 85%) chemotherapy less often than younger patients. A large proportion (40.1%) of patients ≥ 90 in our dataset were classified as FCR 0, unknown stage. Given that the FCR has a completeness of data reaching 97.4% [
10], some of the cases with incomplete data need to be categorized as FCR 0. Hence, the high proportion of FCR 0 among patients ≥ 90 may be explained by such patients receiving palliative treatment upon cancer detection. Furthermore, some cancers may be registered only upon postmortem examination.
A Spanish retrospective study found that CRC patients > 75 years remain undertreated [
26]. Specifically, elderly patients in the study were less likely to undergo surgery and receive chemotherapy, subsequently resulting in lower DSS rates. In this light, our results appear important to highlight, since they offer a solid overview of the situation in Finland, where elderly CRC patients are predominantly treated surgically in the same way as younger patients. Compared with 30-day postoperative OS, we observed a one-year postoperative OS that is significantly worse among patients ≥ 80. The poorer postoperative OS among the older age groups likely results from death due to other causes and the influence of comorbidities. Moreover, we included emergency surgeries in our study. The mortality of the elderly in emergency settings is worse than that in younger patients, which must be taken into account [
27]. The median postoperative hospital stay for elderly patients in our dataset was similar when compared with that in younger patients. The one-year postoperative OS of 62.9–86.3% (average 76.2%) among patients ≥ 75 years old agrees with a retrospective database study of 232 patients, where the one-year postoperative survival was 73.5% among patients > 80 years [
28]. Taken together with the findings from our study concerning overall survival, which included the postoperative hospital stay, this highlights the importance of widely applying standardized treatment and the geriatric assessment of older patients. In a recent population-based Finnish study, risk factors for severe postoperative complications were analyzed, shedding light on various comorbidities to consider when assessing elderly patients preoperatively [
29]. The elderly CRC population is a quite heterogeneous group with multiple comorbidities, although this alone should not serve as the basis for not offering surgery with a curative intent [
30]. As such, the Clinical Frailty Scale (CFS) is a tool for assessing preoperative cognitive and physical independence and activity, recently validated in a Finnish multicenter study [
8]. Furthermore, patients with a lower CFS score were less likely to develop postoperative complications. Previous studies demonstrated the prognostic value of the CFS for elderly patients’ survival [
31,
32]. Thus, frailty and comorbidities are most likely more important factors to evaluate as opposed to age alone when assessing treatment options [
33,
34].
This study has several strengths and limitations. The data source for this study is exceptionally comprehensive and reliable since all healthcare organizations in Finland are obligated by law to report information about diagnosed cancer cases to the Finnish Cancer Registry (FCR). Cause of death data came from Statistics Finland, a reliable source for the cause and date of all deaths in the country. The accuracy of tumor characteristics recorded in FCR is good, with a completeness of data for CRC reaching 97.4% [
10]. The registration of a cancer case is linked to a patient’s unique social security number, making it possible to link patient information across different registries. When a cancer case is reported, the healthcare organization must report the ICD-10 code, the time of diagnosis, a pathologic–anatomical diagnosis, and cancer staging information [
35].
One limitation of this study is that with increasing age, patient groups become smaller. In addition, since our material is registry based, we lacked information on adjuvant treatment and recurrence. More specifically, we received no information on surgery for 51.7% of patients. This may in part be due to the fact that the elderly are more often directed to palliative care, at times due to a lack of information. Thus, the results on postoperative survival should be interpreted with caution. Furthermore, the classification system used by FCR differs from the UICC TNM staging, although the FCR classification is rather thorough, making it possible to categorize many cancer cases. Yet, the specificity of the FCR classification might make comparisons across clinical studies difficult, although it provides exceptional detail on the tumor characteristics and recognizes similar groupings as the TNM stages [
11]. Another strength of this study is its large nationwide cohort of CRC patients, consisting of 27,088 CRC patients, from whom 11,306 were ≥75 years old. As a result, this study sheds light on the outcomes for older CRC patients on a national level from a country with a high standard of health care offered by multiprofessional teams.