Abstract
Evidence has suggested that diabetes may contribute to the initiation and progression of specific types of cancer. Metformin, a biguanide, has become the preferred first-line therapy for the treatment of type 2 diabetes. Metformin is inexpensive, has a proven safety profile and is able to be safely combined with additional antidiabetic agents. In addition to the well-established antidiabetic effects of metformin, there has also been notable interest in its antitumor properties. The present review discusses the emerging role of metformin as an example of an existing drug, used worldwide in the treatment of diabetes, which has been demonstrated to exert significant in vitro and in vivo anticancer activities and has thus been investigated in clinical trials. In gynecologic oncology, metformin has been suggested to exhibit significant treatment efficacy against endometrial cancer. Three studies have demonstrated the potential therapeutic effects of metformin on the survival outcome of patients with ovarian cancer and in ovarian cancer prevention. However, this evidence was based on observational studies. Metformin has been shown to exert no statistically significant beneficial effect on cervical cancer incidence or mortality. By cancer site, the current limited insights highlight the need for clinical investigations and better-designed studies, along with evaluation of the effects of metformin on cancer at other sites.