Adjuvant chemotherapy for stage III colon cancer: does timing matter?

Abstract

Clinical trials commonly mandate that adjuvant chemotherapy for colon cancer should commence within 8 weeks (56 days) of surgery. We investigated the consequences of the timing of adjuvant chemotherapy for stage III colon cancer. This is a retrospective review of all patients with newly diagnosed stage III colon cancer who received adjuvant chemotherapy in 2 provincial centers in 1999 and 2000. The impact of time to adjuvant chemotherapy on overall survival and relapse-free survival was analyzed by the use of univariate and multivariate Cox modeling, adjusting for prognostic factors. Three hundred forty-five subjects were included. Median time to adjuvant chemotherapy was 50 days (range, 20-242 days); in 111 (32.2%) patients, it was beyond 56 days. On univariate analysis, time >56 days was nonsignificantly associated with a hazard ratio of death of 1.31 (P = .12). Similar results were seen for relapse-free survival. Planned exploratory analysis suggests that the commencement of adjuvant chemotherapy up to 10 weeks postsurgery still confers a benefit. Delaying adjuvant chemotherapy in stage III colon cancer beyond 8 to 10 weeks postsurgery appears to be associated with diminished benefit.