Influence of metformin therapy on breast cancer incidence and prognosis

Abstract

Diabetes mellitus type 2 and malignant diseases are among the most frequent causes of morbidity and mortality worldwide. Number of studies showed that breast carcinoma and other cancers are more frequent and have worse prognosis in patients with diabetes. The mechanisms of effect of type 2 diabetes to frequency and prognosis of breast carcinoma are complex and besides a direct effect of insulin resistance, hyperinsulinemia and hyperglycemia, they include the effect of accompanying obesity and anti-diabetic therapy. One of the anti-diabetic drugs that reduces frequency and improves prognosis of breast carcinoma is metformin. Anticancer effects of metformin are indirect (insulin dependent) and direct (insulin independent). Insulin-dependent and insulin-independent antitumor effect of metformin opens the door for implementation of this drug in therapy and prevention of breast cancer and other malignant diseases even in patients without type 2 diabetes. This paper presents literature data on mechanisms of type 2 diabetes impact to the risk of development and prognosis of breast cancer and the anticancer potential of metformin.