Sequential use of bevacizumab and cetuximab in patients with K-RAS wild type advanced colorectal cancer.

e14681 Background: Monoclonal antibodies targeting either VEGF or EGFR have improved the treatment outcomes in patients with advanced colorectal cancer (CRC). Although cetuximab or panitumumab are widely used as the first choice of MoAb in patients with K-RAS wild type tumors, the superiority of those over bevacizumab is still controversial. The primary aim of the study was to evaluate the efficacy of the sequential administration of bevacizumab and cetuximab in patients with K-RAS wild type CRC. Methods: Patients with advanced CRC who were K-RAS wild type and completed at least 2 cycles of MoAb added to doublet chemotherapy back bone were included. The chemotherapy regimens were either FOLFIRI or FOLFOX. Bevacizumab was given at the dose of 5 mg/kg q2w or cetuximab 500 mg/m2 q2w following a loading dose of 800mg/m2. Treatment was continued until disease progression or further 2 cycles after disease stabilization. The patients in bevacizumab group were given cetuximab sequentially following the cessation of bevacizumab. Results: Seventy-three patients (33 bevacizumab and 40 cetuximab groups) were recruited between 2009 and 2013. The chemotherapy backbone was mainly FOLFIRI in both groups. The patient characteristics were similar in both groups. The median age was 56 years, and visceral disease was present in all patients. Median number of cycles of MoAbs were 8 (2-16) in both groups. Objective response rates were 30% in bevacizumab and 44% in cetuximab groups (p = 0.170). Five patients were lost to follow-up (3 in bevacizumab and 2 in cetuximab groups). Median PFS was similar (7.1 vs 7.0 mos., respectively). Though not significant, median overall survival was longer in bevacizumab group compared to cetuximab group (33,4 vs 24,5 months, respectively). The 3-year overall survival rate was significantly higher in the bevacizumab group compared to cetuximab group (45,5% vs 17,2%; p = 0.018, respectively). Both MoAbs were well tolerated with manageable toxicity profile. Conclusions: In conclusion, the sequential use of bevacizumab and cetuximab seems better than cetuximab in patients with K-RAS wild type advanced colorectal cancer. However, the results of the current study need to be further tested in a phase III trial.