Effectiveness of adjuvant fluorouracil in clinical practice: a population-based cohort study of elderly patients with stage III colon cancer.

Although randomized controlled trials (RCTs) consistently show that adjuvant fluorouracil (5-FU) extends the survival of patients with stage III colon cancer, it is not yet known whether this benefit exists in populations underrepresented on clinical trials, particularly the elderly with medical comorbidity treated in the community. In this study, we ask the following: (1) What is the hazard of death associated with adjuvant 5-FU in the general population of elderly stage III colon cancer patients? (2) Does the hazard vary with patient age? In this prospective, nonrandomized, population-based cohort study of 3,357 elderly Medicare beneficiaries who had undergone resection of stage III colon cancer according to the Surveillance, Epidemiology, and End-Results registries, we use propensity score matching to compare the all-cause mortality of patients who received 5-FU to matched untreated patients. 5-FU reduces the hazard of death by 27% (hazard ratio, 0.73; 95% confidence interval [CI], 0.65 to 0.82) across the 6 years of our data in a Cox model. At 5 years, 52.7% (95% CI, 49.6% to 55.6%) of the treated and 40.7% (95% CI, 38.1% to 43.4%) of the matched untreated are still alive. We find that these effects do not diminish with advancing patient age. The survival benefit of adjuvant 5-FU that has been demonstrated in participants of RCTs is also evident in a population sample of elderly Medicare beneficiaries with stage III colon cancer treated in the community. Furthermore, this survival benefit does not appear to diminish with patient age. These findings support the continued use of adjuvant 5-FU in the general population of elderly patients with stage III colon cancer and suggest that oncologists in the community are practicing at a high level of effectiveness.