Bevacizumab-containing regimens after cetuximab failure in Kras wild-type metastatic colorectal carcinoma

Bevacizumab and cetuximab both improve treatment efficacy when administered with chemotherapy for metastatic colorectal carcinoma (mCRC). Cetuximab has enhanced efficacy in Kras wild-type tumors. However, inferior outcomes have been demonstrated concerning the concurrent use of bevacizumab and cetuximab with chemotherapy. There is an urgent need to define the optimal sequence of use of these two agents. With regard to the pre-clinical data that increased VEGF expression is associated with acquired resistance to anti-EGFR antibody, we performed a retrospective analysis on the outcomes of patients who received bevacizumab-containing regimens after cetuximab failure in Kras wild-type mCRC. From January 2006 to December 2011, patients who received bevacizumab-containing regimens for mCRC in our institution were reviewed. Patients were eligible for further analysis if the following criteria were met: i) Kras wild-type mCRC; ii) chemotherapy and cetuximab received as immediate prior treatment; iii) chemotherapy and bevacizumab received as the index line of treatment; and iv) imaging conducted for response evaluation. Outcome measures included median progression-free survival (mPFS) and objective response rate (ORR). Targeted adverse events were recorded in accordance with two prospective observational cohort studies; the BRiTE and BEAT studies. Fifty patients who received bevacizumab-containing regimens were reviewed and 18 of them met the criteria for further analysis. After a median follow-up of 12.1 months, the mPFS for the total group of patients was 26.3 weeks (95% CI, 19.5-33.0 weeks) with an ORR of 38.9%. Two patients (11.1%) had hypertension that required additional anti-hypertensive drugs and one patient did not survive due to a bowel perforation. No arterial thromboembolic events (ATEs), post-operative wound-healing complications (POWHCs) or grade III/IV bleeding were observed. In patients with Kras wild-type mCRC, bevacizumab-containing regimens following cetuximab failure have modest activity and manageable toxicity.