Oxaliplatin As Adjuvant Therapy for Colon Cancer: Updated Results of NSABP C-07 Trial, Including Survival and Subset Analyses

Abstract

The National Surgical Adjuvant Breast and Bowel Project (NSABP) C-07 trial demonstrated that the addition of oxaliplatin to fluorouracil plus leucovorin (FULV) improved disease-free survival (DFS) in patients with stage II or III colon cancer. This analysis is the first publication of overall survival (OS) for the NSABP C-07 study. We updated DFS and examined both end points in clinically relevant patient subsets. Other studies have identified patients age 70 or older and those with stage II disease as patient subsets in which oxaliplatin may not be effective. We investigated toxicity as a driver of divergent outcomes in these subsets. In all, 2,409 eligible patients with follow-up were randomly assigned to either FULV (FU 500 mg/m(2) by intravenous [IV] bolus weekly for 6 weeks; leucovorin 500 mg/m(2) IV weekly for 6 weeks of each 8-week cycle for three cycles) or FLOX (FULV plus oxaliplatin 85 mg/m(2) IV on days 1, 15, and 29 of each cycle). With 8 years median follow-up, OS was similar between treatment groups (hazard ratio [HR], 0.88; 95% CI, 0.75 to 1.02; P = .08). FLOX remained superior for DFS (HR, 0.82; 95% CI, 0.72 to 0.93; P = .002). The effect of oxaliplatin on OS did not differ by stage of disease (interaction P = .38 for OS; interaction P = 0.37 for DFS) but did vary by age for OS (younger than age 70 v 70+ interaction P = .039). There was a similar trend for DFS (interaction P = .073). Oxaliplatin significantly improved OS in patients younger than age 70 (HR, 0.80; 95% CI, 0.68 to 0.95; P = .013), but no positive effect was evident in older patients. Overall, the addition of oxaliplatin to FULV has not been proven to extend OS in this trial, but the DFS effect remained strong. Unplanned subset analyses suggest a significant OS effect of oxaliplatin in patients younger than age 70.