Study Results: Can Metformin Reduce Breast Cancer Incidence?

The diabetes drug, Metformin, commonly prescribed for management of adult onset of diabetes shows promising results in a clinical comparison of postmenopausal women for prevention of breast cancer development.

Study:  68,019 postmenopausal women, including 3,40l with diabetes at entry point, were observed for a mean of 11.8 years. During this time 3,237 invasive breast cancers were diagnosed and were confirmed by pathology reports.

Results Compared with that in women without diabetes, breast cancer incidence in women with diabetes differed by diabetes medication type (P = .04). Women with diabetes receiving medications other than Metformin had a slightly higher incidence of breast cancer (hazard ratio [HR], 1.16; 95% CI, 0.93 to 1.45), and women with diabetes who were given Metformin had lower breast cancer incidence (HR, 0.75; 95% CI, 0.57 to 0.99). The association was observed for cancers positive for both estrogen receptor and progesterone receptor and those that were negative for human epidermal growth factor receptor 2.

This one study presents evidence that Metformin may reduce breast cancer incidence.  Metformin has been used successfully for many years to control blood sugar. Additional studies are needed to confirm this finding in search for a drug that can be used for prevention and management of breast cancer.

Source:  American Society of Clinical Oncology, June 2012