The effects of metformin on ovarian cancer: an updated systematic review and meta-analysis

Objective: The potential therapeutic effects of metformin on several cancers have been reported. However, there is no consensus on whether metformin has anti-tumor impact on ovarian cancer. We performed this systematic review and meta-analysis to assess the effect of metformin on ovarian cancer. Methods: We conducted searches of PubMed, EMBASE and the Cochrane Central Register of Controlled Trials to identify studies evaluating risk or survival data of ovarian cancer in diabetic patients taking metformin versus those not. All articles were reviewed independently by two authors with a standardized approach, to extract study design, patient characteristics, metformin exposure, and clinical outcomes. The meta-analysis estimating ovarian cancer risk was done using a random-effect model. Results: Among 9 included studies, 4 studies determined the effect of metformin on survival in diabetic ovarian cancer patients, while the rest 5 studies assessed whether metformin could protect diabetes patients from ovarian cancer occurrence. The findings of studies reporting survival outcomes indicated that metformin may prolong overall, disease-specific, and progression-free survival in ovarian cancer patients. The results of studies reporting the effect of metformin on preventing ovarian cancer were meta-analyzed, which demonstrated that metformin significantly decreased incidence of ovarian cancer among diabetic patients with the pooled odds ratio of 0.54 (95% confidence interval: 0.32-0.93). Conclusions: Our findings showed that metformin can reduce ovarian cancer risk and may prolong ovarian patents’ survival among diabetic patients.