Estimating the Adjuvant Chemotherapy Effect in Elderly Stage II and III Colon Cancer Patients in an Observational Study

PURPOSE: Adjuvant chemotherapy has been known as a standard treatment for patients with resected colon cancer. However, in elderly colon cancer patients, the characteristics of patients are heterogeneous with regard to life expectancy and comorbidities. Thus, with regard to the effectiveness of adjuvant chemotherapy for colon cancer, it is difficult to extrapolate data of clinical trials from the younger into the older general population. METHODS: Data for 382 elderly colon cancer patients were analyzed: 217 in Stage II and 165 in Stage III. The efficacy of adjuvant chemotherapy was evaluated in elderly colon cancer patients after a match by the propensity score method. RESULTS: For matched patients with Stage II colon cancer, there was no significant efficacy of adjuvant chemotherapy in the risk of death during all follow-up periods (P-value, 0.06-0.37). Though there was a tendency that the adjuvant chemotherapy reduces the death rate during the follow-up periods, it was not statistically significant. In the case of Stage III, the adjuvant chemotherapy was significantly effective in matched patients for 5-year (hazard ratio [HR], 0.69; 95% confidence interval [CI], 0.30-0.90) and overall survival (HR, 0.56; 95% CI, 0.34-0.94). CONCLUSIONS: Adjuvant chemotherapy for elderly patients with Stage II colon cancer is not effective, whereas elderly patients with Stage III with adjuvant chemotherapy appear to have a better survival rate in the general population.ope