The study, published in the journal Diabetes Care, reveals that metformin, the most commonly used drug for type 2 diabetes, may have anti-cancer effects. Dr. Christoph R. Meier and his colleagues (University Hospital Basel in Switzerland) identified women who have used the diabetes drug metformin for more than five years and noticed that they may have 56 % lower risk of breast cancer than diabetic women on other treatments.

     The findings are based on the medical records of UK women more than 1400 in number between the ages of 30 and 79 who were being treated for type 2 diabetes. The researchers identified 305 women who had been diagnosed with breast cancer, and matched each with three or four cancer-free women the same age. They then looked at the women's diabetes medication history to look for links to breast cancer risk.

     Researchers at Harvard University are currently developing a large clinical trial to test whether using metformin after standard treatment for early breast cancer helps prevent cancer recurrence.

     Metformin lowers insulin levels by blocking the liver's production of glucose and increasing the body's glucose absorption from the blood. This insulin reduction could be the clue to the drug's link to a lower breast cancer risk, observes the research team.