Adjuvant chemotherapy use for Medicare beneficiaries with stage II colon cancer

Clinical trials have not demonstrated that adjuvant chemotherapy improves survival for patients with resected stage II colon cancer. Nevertheless, patients may receive this treatment despite its uncertain benefit. The objective of this study was to determine the extent to which adjuvant chemotherapy is used for patients with stage II colon cancer.

Using the Surveillance, Epidemiology, and End Results-Medicare linked database, we identified 3,151 patients aged 65 to 75 with resected stage II colon cancer and no adverse prognostic features. The primary outcome was chemotherapy use within 3 months of surgery ascertained from claims submitted to Medicare. Relationships between patient characteristics and adjuvant chemotherapy use were measured and their significance was assessed using multivariable logistic regression. Survival for treated and untreated patients was compared using a Cox model.

Twenty-seven percent of patients received chemotherapy during the 3 postoperative months. Younger age at diagnosis, white race, unfavorable tumor grade, and low comorbidity were each associated with a greater likelihood of receiving treatment. Sex, the number of examined lymph nodes in the tumor specimen, the urgency of the surgical admission, and median income was each unrelated to treatment. Five-year survival was 75% for untreated patients and 78% for treated patients. After adjusting for known between-group differences, the hazard ratio for survival associated with adjuvant treatment was 0.91 (95% confidence interval, 0.77 to 1.09).

A substantial percentage of Medicare beneficiaries with resected stage II colon cancer receive adjuvant chemotherapy despite its uncertain benefit.