Chemotherapy plus bevacizumab as an optimal first-line therapeutic treatment for patients with right-sided metastatic colon cancer: a meta-analysis of first-line clinical trials

BACKGROUND: Monoclonal antibodies of anti-epidermal growth factor receptor (EGFR) have been recommended as first-line therapy for patients with left-sided metastatic colorectal cancer (mCRC) with wild-type RAS. The effect of tumour laterality on antivascular endothelial growth factor antibody and how to optimise targeted therapies for the right-sided cases remain controversial. PATIENTS AND METHODS: A comprehensive meta-analysis enrolling 16 first-line clinical trials was performed to evaluate the efficacy of chemotherapy alone and chemotherapy plus targeted therapies for patients with mCRC with right primary tumour site, and we validated the results in metastatic setting (14 trials containing 4306 patients with unresectable mCRC). RESULTS: Here, we found that progression-free survival (PFS) (combined HR 1.30, 95% CI 1.17 to 1.44) and overall survival (OS) (combined HR 1.46, 95% CI 1.32 to 1.62) of the right-sided patients were significantly inferior to the left-sided individuals receiving chemotherapy alone in overall population, regardless of race. Similar results were also observed in metastatic setting. OS of patients with left-sided mCRC receiving chemotherapy plus bevacizumab was superior to the right-sided individuals (combined median survival ratio (MSR)=1.23, 95% CI 1.08 to 1.39 for overall population; combined MSR=1.23, 95% CI 1.05 to 1.45 for metastatic setting), especially for wild-type RAS and mixed population. Moreover, the right-sided patients benefited more from chemotherapy plus bevacizumab comparing with chemotherapy alone in both overall population and metastatic setting. Importantly, the RAS-wild right-sided patients achieved longer PFS (combined HR 0.67, 95% CI 0.52 to 0.88) and OS (combined HR 0.74, 95% CI 0.56 to 0.98) from chemotherapy plus bevacizumab comparing with chemotherapy associated with anti-EGFR agents. CONCLUSIONS: Patients with right-sided mCRC show impaired chemosensitivity, and chemotherapy plus bevacizumab can be an optimal first-line therapeutic regimen for the RAS-wild patients with right-sided mCRC.