Primary Tumor Location as a Predictive Factor for First-line Bevacizumab Effectiveness in Metastatic Colorectal Cancer Patients

Background: Published papers reported contradictory results about the correlation between bevacizumab effectiveness and primary tumor location of metastatic colorectal cancer (mCRC). Methods: 740 mCRC patients treated with chemotherapy (CT group) and 244 patients treated with bevacizumab plus chemotherapy as first-line setting (CT + B group) were included. Propensity score analyses were used for patients' stratification and matching. Kaplan-Meier curves with log-rank tests were used to detect different overall survival (OS). Results: Patients in CT + B group had similar OS comparing with CT group only when the primary tumor located at right-side colon (20.2 for CT + B versus 19.7 months for CT group, p = 0.269). For left-side colon and rectal cancer patients, significantly longer OS were observed in CT + B than CT group. Conclusion: Our data suggested only patients with left-side colon or rectal cancer could get survival benefit from the addition of bevacizumab to first-line chemotherapy.