First-line cetuximab improves the efficacy of subsequent bevacizumab for RAS wild-type left-sided metastatic colorectal cancer: an observational retrospective study

The optimal targeted therapy sequence in patients of RAS wild-type left-sided metastatic colorectal cancer (mCRC) remains controversial, and few studies focus on the impact of first-line targeted agents on second-line ones. We enrolled 101 left-sided mCRC patients with RAS wild-type status, of which 50 cases received bevacizumab plus chemotherapy in both first-line and second-line therapies (Group A) and 51 cases received first-line cetuximab plus chemotherapy followed by second-line bevacizumab-containing regimens (Group B). The progression free survival (PFS) and overall survival (OS) from start of first-line (PFS 1nd and OS 1nd) and second-line (PFS 2nd and OS 2nd) therapy were compared between the two groups. PFS 1nd was comparable (10.0 vs 10.4 months; p=0.402), while PFS 2nd (4.6 vs 7.9 months; p=0.002), OS 1nd (26.8 vs 40.0 months; p=0.011), and OS 2nd (15.2 vs 22.3 months; p=0.006) were all poorer in group A compared with group B. Our study in combination with previous clinical data suggest that first-line application of cetuximab may provide a favorable condition for promoting the effect of subsequent bevacizumab, thus representing the optimal targeted therapy sequence in patients of RAS wild-type left-sided mCRC.