Effect Of Adding Bevacizumab To Chemotherapy On Pathologic Response To Preoperative Systemic Therapy Of Potentially Resectable Colorectal Cancer Liver Metastases (Clm): A Systematic Review And Meta-Analysis

151 Background: Perioperative CT and resection of CLM are potentially curative therapies in the management of metastatic colorectal cancer (mCRC). Retrospective studies suggest that preoperative bevacizumab increases pathologic response, which is a surrogate endpoint for overall survival (OS). We conducted the first systematic review and meta-analysis addressing the effect of bevacizumab on pathologic response to preoperative therapy of CLM. Methods: We systematically searched PubMed, Cochrane Library, Embase and LILACS from January/2004 to August/2019 for studies that have compared the pathologic response to CT plus bevacizumab versus CT alone as preoperative therapy of potentially resectable CLM. The primary endpoint was pathologic complete response (pCR). Secondary endpoint was major response (MaR) (0-50% residual cancer cells or tumor regression grade (TRG) 1-3 in liver specimen). The likelihood of preoperative therapy being associated with pCR or MaR has been expressed by odds ratio (OR) and 95% confidence intervals (CI) using a random-effects model. Results: Of the 1,319 studies yielded by the search, 9 studies were retained, totaling 1,202 patients (516 CT plus bevacizumab versus 686 CT alone). The addition of bevacizumab to CT increased the pCR rate, but it did not reach statistical significance (OR: 1.24, 95% CI 0.81 – 1.92, p = 0.32). However, MaR was significantly superior in the bevacizumab group (OR: 2.20, 95% CI 1.47 – 3.29, p < 0.001). A higher percentage of patients have been submitted to oxaliplatin-based regimens in bevacizumab group compared to CT alone group (84% versus 68%, p < 0.001), while irinotecan-based regimens have been more common in the CT alone group (11% versus 28%, p < 0.001). Conclusions: The addition of bevacizumab to preoperative CT was associated with higher rates of pathologic response in liver resection of CLM. Anti-angiogenics might potentially improve the recurrence-free survival and OS in the management of potentially resectable CLM and should be evaluated as preoperative therapy in randomized clinical trials.