Adjuvant chemotherapy patterns and clinicopathological factors associated with survival in patients aged 70 years and older with resected stage II–III colon cancer: a single-center real-world study
Aims: Older adults are underrepresented in adjuvant colon cancer trials, leaving uncertainty regarding oxaliplatin benefit and optimal treatment duration. This study evaluated the associations of adjuvant chemotherapy patterns, treatment duration, and clinicopathological factors with overall survival (OS) and disease-free survival (DFS) in patients aged ≥70 years with resected stage II-III colon cancer.Methods: This single-center retrospective study included patients aged ≥70 years with resected stage II-III colon cancer. Survival outcomes were analyzed using Kaplan-Meier methods and Cox regression analyses.Results: Forty-six patients were included; the mean age was 74.39±4.48 years, and 56.5% were male. Overall, 56.5% received oxaliplatin-containing chemotherapy, and 71.7% completed six months of treatment. Disease progression occurred in 41.3% of patients, and 28.3% died. Estimated mean OS and DFS were 100.9 months and 84.2 months, respectively. Although six-month chemotherapy was associated with OS and showed a borderline association with DFS in reduced exploratory Cox models, these associations were attenuated and were no longer statistically significant in the 6-month landmark sensitivity analysis. Oxaliplatin-containing chemotherapy was not significantly associated with OS or DFS in the overall cohort. Conclusion: In this retrospective single-center cohort of patients aged ≥70 years with resected stage II–III colon cancer, sixmonth adjuvant chemotherapy was associated with longer survival in conventional analyses but was no longer statistically significant in the 6-month landmark sensitivity analyses. Therefore, this finding should be interpreted cautiously because of potential immortal time bias, survivor selection, treatment-selection bias, and residual confounding. Oxaliplatin-containing chemotherapy was not significantly associated with OS or DFS in the overall cohort. These findings should be considered hypothesis-generating and should not be interpreted as causal evidence regarding optimal treatment duration or oxaliplatin benefit in older adults.