Age and Adjuvant Chemotherapy Use After Surgery for Stage III Colon Cancer

Background: Randomized trials have established that 5-fluorouracil-based adjuvant chemotherapy following resection of stage III colon cancer reduces subsequent mortality by as much as 30%. However, the extent to which adjuvant therapy is used outside the clinical trial setting, particularly among the elderly, is unknown. Methods: A retrospective cohort study utilizing the Surveillance, Epidemiology, and End Results/Medicare-linked database identified 6262 patients aged 65 years and older with resected stage III colon cancer. The primary outcome was chemotherapy use within 3 months of surgery, as ascertained from Medicare claims. We examined the extent to which age at diagnosis was associated with adjuvant chemotherapy usage, and we adjusted for potential confounding based on differences in other patient characteristics with the use of multiple logistic regression. All P values were two-sided. Results: Age at diagnosis was the strongest determinant of chemotherapy: 78% of patients aged 65–69 years, 74% of those aged 70–74 years, 58% of those aged 75–79 years, 34% of those aged 80–84 years, and 11% of those aged 85–89 years received postoperative chemotherapy. The age trend remained pronounced after adjustment for potential confounding based on variation in patients' demographic and clinical characteristics and after exclusion of patients with any evident comorbidity (all P values