Preventive and Therapeutic effects of Metformin in Cancer: A Meta-Analysis of RCT and Cohort Studies

Background: There is discrepancy of results among various individual and me-ta-analytical studies about the effect of metformin on cancer risk and patients’ survival. Therefore, we have conducted a comprehensive, updated meta-analysis to evaluate the preventive and therapeutic effects of metformin for cancer patients, as well as the inci-dence of adverse reactions, among metformin users. Methods: A total of 18 studies (10 cohort studies and 8 randomized controlled trials) in-volving 1,300,820 participants from Europe, North America, and Asia were included in this meta-analysis. Results: No significant association was found between metformin use and overall survival (Hazard ratio = 1.02; 95% CI, 0.80 – 1.30) and progressive-free survival (Hazard ratio = 1.00; 95% CI, 0.76 – 1.31). In addition, the summary risk estimates for adverse reactions of metformin were not statistically significant between intervention and control groups (Risk Ratio = 1.11; 95% CI, 0.94 – 1.31). However, metformin use was associated with a reduction in cancer risk (Hazard ratio = 0.90, 95% CI, 0.86 – 0.94). Conclusion: Metformin does not significantly prolong the overall survival and progressive-free survival of cancer patients, but it may effectively reduce the risk of cancer occurrence.