This systematic review and meta-analysis aims to evaluate the additive effect of bevacizumab when combined with first-line chemotherapy in metastatic colorectal cancer (mCRC).We searched EMBASE, MEDLINE, the Cochrane Library in April 2018. When possible, data were pooled to estimate summary effects. The present analysis evaluated treatment related efficacy based on progression-free survival (PFS) and overall survival (OS). The analysis was performed to define the overall effect and the effect observed in currently used chemotherapy regimens.Seven randomised studies were included. In the analysis of the overall effect, PFS (hazard ratio [HR] 0.71, p 0.00001) and OS (HR 0.85, p = 0.0008) clearly favoured bevacizumab plus chemotherapy versus chemotherapy alone. When the analysis was focused on currently used chemotherapy excluding 5-FU bolus regimens and including only infusional 5-FU plus irinotecan or oxaliplatin, the addition of bevacizumab prolonged PFS (HR 0.79, p 0.0001) but not OS (HR 0.92, p = 0.18). However, addition of bevacizumab to fluoropyrimidine monotherapy lead to a significant prolongation of PFS (HR 0.57, p 0.00001) and OS (HR 0.83, p = 0.03).The present meta-analysis demonstrates that the effect of bevacizumab on survival is not consistent throughout the included regimens. Considering only presently used regimens, a significant effect on PFS and OS was only observed when bevacizumab was added to fluoropyrimidine monotherapy.
