One year of bevacizumab added to 6 months of leucovorin/fluorouracil/oxaliplatin (mFOLFOX6) does not significantly prolong disease-free survival (DFS) in stages II and III colon cancer, according to recently released results of the National Surgical Adjuvant Breast and Bowel Project (NSABP) Protocol C-08 (J Clin Oncol. 2011;29:11-16). The study did find, however, a significant transient effect during bevacizumab exposure.
Researchers randomized 2710 patients to mFOLFOX6 alone for 6 months or mFOLFOX6 for 6 months plus bevacizumab for 12 months beginning concurrently with chemotherapy. With a median follow-up of 35.6 months, DFS for patients in the bevacizumab group did not significantly increase (hazard ratio [HR], 0.89; 95% confidence interval [CI], 0.76-1.04; P = .15). In the bevacizumab group, treatment effect was similar for both stages of disease (interaction P = .68)
Researchers observed a difference in the effect of bevacizumab on DFS before and after a 15-month landmark (time-by-treatment interaction P <.0001), with a strong effect before 15 months (HR, 0.61; 95% CI, 0.48-0.78; P <.001) and no significant effect after 15 months (HR, 1.22; 95% CI, 0.98-1.52; P = .076). They postulated that this effect could reflect a biologic effect during bevacizumab exposure, which will require confirmation from other studies.