Comparison of cetuximab to bevacizumab as the first-line bio-chemotherapy for patients with metastatic colorectal cancer: superior progression-free survival is restricted to patients with measurable tumors and objective tumor response--a retrospective study.

PURPOSE: We aimed to compare the treatment efficacy of cetuximab versus bevacizumab in combination with either irinotecan-based or oxaliplatin-based regimens (targeted triplet) as the first-line treatment for patients with metastatic colorectal cancer.

METHODS: Between April 2005 and March 2012, patients (n = 158) diagnosed with metastatic colorectal cancer after at least four courses of first-line bevacizumab-based (n = 95) or cetuximab-based triplet (n = 63) were retrospectively analyzed. The KRAS genotypes were sequenced for all patients. The Kaplan-Meier method was used for survival analysis, and Cox proportional hazards models were used for univariate and multivariate analyses.

RESULTS: Cetuximab-based triplet was associated with a higher objective response rate (66.0 vs. 47.2 %, p = 0.037) and a higher conversion rate to resectability (39.7 vs. 20.0 %, p = 0.007) compared to bevacizumab-based triplet. Compared with bevacizumab-based triplet, cetuximab-based triplet significantly increased progression-free survival in patients with measurable metastatic colorectal cancer who achieved objective tumor response (responders) (median 13.1 vs. 10.5 months, p = 0.023), but no significant increase was observed for overall survival. After adjustment for group differences in baseline characteristics and combined chemotherapy agents, cetuximab-based triplet remained an independent determinant of progression-free survival in responders as compared with bevacizumab-based triplet. KRAS mutation was not a prognostic factor in patients with metastatic colorectal cancer.

CONCLUSIONS: As compared with bevacizumab-based triplet, cetuximab-based triplet as the first-line treatment of metastatic colorectal cancer was associated with better progression-free survival in patients with measurable tumors who achieved objective tumor response to bio-chemotherapy.