Effect of age on survival benefit of adjuvant chemotherapy in elderly patients with stage III colon cancer

OBJECTIVES: To estimate the modifying effect of age on the survival benefit associated with adjuvant chemotherapy receipt in elderly patients with a diagnosis of Stage III colon cancer. DESIGN: Observational, retrospective cohort study using two samples: an overall sample of 7,182 patients to provide externally valid analyses and a propensity score-matched sample of 3,016 patients to provide more internally valid analyses by reducing the presence of treatment endogeneity. An interval-censored survival model with a complementary log-log link was used. Hazard ratios and 95% confidence intervals were obtained for all regressions. SETTINGS: Data from the National Cancer Institute's Surveillance, Epidemiology and End Results database and the linked Medicare enrollment and claims database were used. PARTICIPANTS: Selected patients were aged 66 and older and had a diagnosis of Stage III colon cancer. Patients were followed from surgery to time of death or censorship. MEASUREMENTS: The outcome was colon cancer-specific death during the follow-up period. Receipt of adjuvant chemotherapy was measured according to the presence of a claim for 5-fluorouracil or leucovorin within 6 months after surgery. RESULTS: All elderly patients had a significant survival benefit associated with adjuvant chemotherapy receipt, although the survival benefit of adjuvant chemotherapy was not uniform across all age groups. CONCLUSION: These findings have important clinical and policy implications for the risk-benefit calculation induced by treatment in older patients with Stage III colon cancer. The results suggest that there is a benefit from chemotherapy, but the benefit is lower with older age.