Oncological Impact and Benefit of Adjuvant Chemotherapy for Older Patients With Colon Cancer: A Multi-Institutional Retrospective Study

Aim: With the proportion of older patients diagnosed with colon cancer increasing with global life expectancy, the oncological benefits of adjuvant chemotherapy and optimal treatment selection in older patients remain controversial. We evaluated the risk-stratified long-term oncological impact of adjuvant chemotherapy in older patients with colon cancer. Methods: This multi-institutional retrospective study, conducted at five university hospitals, involved 394 older patients (age ≥ 75 years), selected from among 1585 patients who underwent curative resection for high-risk stage II and stage III colon cancer. Using an intention-to-treat analysis, disease-free survival and overall survival were compared between patients who received adjuvant chemotherapy and those who did not. Risk stratification-based subgroup analyses for high-risk stage II, low-risk stage III (T1-3N1), and high-risk stage III (T4 or N2) were performed. Results: Among 394 older patients, 184 (46.7%) received adjuvant chemotherapy. Multivariate analysis identified adjuvant chemotherapy as an independent favorable prognostic factor for overall survival (hazard ratio [95% confidence interval] 0.353 [0.197–0.630], p < 0.001). In subgroup analysis, adjuvant chemotherapy significantly improved both overall survival and disease-free survival only in the high-risk stage III group (5-year overall survival rate, 78.6% vs. 49.1%, p = 0.006, and 5-year disease-free survival rate, 69.3% vs. 48.2%, p = 0.024, respectively). Conclusion: Adjuvant chemotherapy provides significant survival benefits in older patients with high-risk stage III, but not high-risk stage II or low-risk stage III, colon cancer. Risk stratification, rather than age, should guide treatment decisions.