Survival Associated with 5-Fluorouracil–Based Adjuvant Chemotherapy among Elderly Patients with Node-Positive Colon Cancer

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Abstract
Randomized clinical trials have demonstrated the efficacy of adjuvant 5-fluorouracil (5-FU)-based chemotherapy after surgical resection of node-positive colon cancer. Although this treatment became the standard in 1990 following a National Institutes of Health Consensus Conference, among those at least 65 years of age it is less likely to be offered to older or nonwhite patients. To determine the association between 5-fu–based chemotherapy and survival in older patients. Retrospective cohort study. Combined database of the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program and Medicare. 4768 patients 65 years of age or older who received a diagnosis of node-positive colon cancer from 1992 to 1996, were covered by Medicare Parts A and B, and resided in the population covered by the SEER program. Propensity scores to control for known predictors of receiving treatment, Cox proportional-hazards models to assess the association of 5-FU therapy with survival, and sensitivity analyses to estimate the possible effects of unknown confounders. Fifty-two percent of patients received 5-FU therapy. For this sample, the hazard ratio for death associated with 5-FU therapy was 0.66 (95% CI, 0.60 to 0.73). Confounding could have accounted for this association only if an unmeasured confounder were extremely unequally distributed between the treated and untreated groups or increased mortality by at least 50%. 5-Fluorouracil adjuvant therapy is significantly associated with reduced mortality in older patients, similar to the association found in randomized, controlled trials among younger patients. More frequent use of 5-FU therapy in older patients would probably reduce death from colon cancer.