EP265 - Oncological Impact of Adjuvant Chemotherapy in Elderly Colorectal Cancer Patients: Does it have a benefit? A Multi-Institutional Retrospective Study

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Purpose/Background: As global life expectancy has increased, there is a rising percentage of elderly patients being diagnosed with colorectal cancer. However, in the elderly patients, the adjuvant chemotherapy is often omitted due to concerns about their intolerance and side effects of that. Moreover, the oncological role of adjuvant chemotherapy in elderly patients is not clear. The aim of this study is to evaluated the long-term oncological impact of adjuvant chemotherapy for colorectal cancer in elderly patients.

Methods/Interventions: Data of patients with high-risk stage II and stage III colorectal cancer who underwent curative resection from January 2011 to December 2015 were extracted from five university hospitals. Elderly patients were defined as 75 years of age or older. Data on adjuvant chemotherapy such as whether chemotherapy was performed, type of cytotoxic agent, duration of treatment were collected. The chemotherapy group was defined as patients who had undergone the treatment for at least 3 months. The oncological outcomes, such as disease-free survival (DFS) and overall survival (OS), were compared. Subgroup analysis was performed by dividing the patients into three groups depending on their stage. [High-risk stage II (stage II with high risk factor), Low-risk stage III (T1-3 and N1), and High-risk stage III (T4 or N2)].

Results/Outcomes: A total of 2128 high-risk stage II and stage III colorectal cancer patients were identified. Totally, 479 (22.5%) patients were elderly patients and the mean age of those was 79.9±4.3 years. Among them, 183 (38.2%) patients underwent adjuvant chemotherapy. FOLFOX, FL, and oral capecitabine were performed in 87 (47.5%), 74 (40.4%), and 22 (12.0) patients, respectively. The patients in chemotherapy group were younger (78.1 vs. 81.0 years, p < 0.001) and had advanced N stage (N2: 28.4% vs. 21.3%, p=0.002) than those in no chemotherapy group. Adjuvant chemotherapy was not a good prognostic factor for DFS [hazard ratio (HR) 0.710, 95% confidence interval (CI) 0.484-1.040], but was a good prognostic factor for OS [HR 0.559, 95% CI 0.336-0.930]. In subgroup analysis, adjuvant chemotherapy was not associated with DFS and OS in High-risk stage II and Low-risk stage III groups, respectively. However, in High-risk stage III colorectal cancer, multivariate analysis revealed that adjuvant chemotherapy was significantly associated with good DFS [HR 0.549, 95% CI 0.312-0.967] and OS [HR 0.367, 95% CI 0.177-0.764], respectively. The 5-year DFS rates of the patients who underwent chemotherapy and those who did not were 75.5% vs. 68.7% (p=0.076). In subgroup analysis, the 5-year DFS rates of the patients who underwent chemotherapy and those who did not were 86.5% vs. 80.0% in High-risk stage II (p=0.462), 77.0% vs. 68.9% in Low-risk stage III (p=0.161), and 65.4% vs. 53.4% in High-risk stage III (p=0.046), respectively.

Conclusion/Discussion: This study demonstrated that adjuvant chemotherapy in elderly patients aged 75 years or older significantly improved the oncological outcomes in High-risk stage III colorectal cancer, but not in High-risk stage II and Low-risk stage III colorectal cancers. Therefore, indication for adjuvant chemotherapy should be established in elderly colorectal cancer patients different for those in general younger patients.