Defective Mismatch Repair and Benefit from Bevacizumab for Colon Cancer: Findings from NSABP C-08

National Surgical Adjuvant Breast and Bowel Project protocol C-08 tested the worth of adding 1 year of bevacizumab to oxaliplatin-based standard adjuvant chemotherapy regimen in the treatment of stage II/III colon cancer. Although the overall result was negative, the possibility that a molecularly defined subset could benefit from bevacizumab cannot be ruled out. We performed post hoc Cox regression analyses to test for marker-by-treatment interactions for standard pathological features and survival analyses using the KaplanMeier method. All statistical tests were two-sided and considered statistically significant at the .05 level. Patients diagnosed with mismatch repair defective (dMMR) tumors derived statistically significant survival benefit from the addition of bevacizumab (hazard ratio [HR] 0.52; 95% confidence interval [CI] 0.29 to 0.94; P .02) in contrast with no benefit in patients diagnosed with mismatch repair proficient tumors (HR 1.03; 95% CI 0.84 to 1.27; p .78; P-interaction .04). Although a post hoc finding, this data suggests that a molecularly defined subset of colon cancer patients may derive clinical benefit from antiangiogenesis agents and underscores the need for independent validation in other clinical trials.