The present status of metformin in fertility-preserving treatment in atypical endometrial hyperplasia and endometrioid endometrial cancer

Progestin therapy is the main fertility-sparing treatment for women with endometrial cancer (EC) and atypical endometrial hyperplasia (AEH). However, still 15-25% of these women failed to achieve complete response (CR) and then lost their fertility after definitive surgery. Metformin has been demonstrated to play an anti-cancer role in multiple cancers including EC. Several studies also suggested metformin had potential benefit in improving the therapeutic outcome of fertility-preserving treatment alongside with progestin. This review has discussed existed evidence regarding the effect of metformin combined with progestin for women with AEH and EC who desire childbearing. Nevertheless, the therapeutic effect of metformin varied in different studies due to the high heterogeneity in the patient’s characteristics, the inconsistency in dose and treatment duration of metformin, the combined use of hysteroscopy, the insufficient sample size and underpowered study-design. Therefore, care should be taken when interpreting the current results on this issue. Till now, there is still no strong evidence supporting the use of metformin in fertility-preserving treatment in AEH and EEC patients. Further research is needed to provide high-quality data to validate the role of metformin as adjunctive therapy alongside with progestin to preserve fertility for AEH and EEC patients.