Metformin and endometrial cancer risk: A Meta-analysis

Objective: To assess the association between metformin and endometrial cancer risk by conducting a meta-analysis. Methods: A comprehensive search of electronic databases, conference abstracts, and clinical trial registers was performed to identify available evidence. Studies that evaluated the association between metformin use and endometrial cancer risk were considered. We pooled relative risk (RR) estimates with 95% confidence intervals (CIs) by using either a fixed-effects or a random-effects model. Results: Nine studies (1 randomized controlled trial, 5 cohort studies, and 3 case-control studies) involving more than 1.20 million participants and 7,762 cases of endometrial cancer met eligibility criteria. There was no evidence of an association between metformin use and endometrial cancer risk (RR, 0.96; 95% CI, 0.80 to 1.16). Similarly, the pooled data showed that metformin use was not significantly associated with endometrial cancer risk in patients with diabetes (RR, 0.93; 95% CI, 0.78 to 1.11). In subgroup analyses, the results were stable across different study designs and comparisons, and remained unchanged after adjusting for age and BMI or obesity. Conclusions: The current meta-analysis suggests that metformin has no chemopreventive effect against endometrial cancer.