A diabetes drug already on the market shelves may be the next phenomenal breast cancer treatment.

Metformin is the drug that is easily available at all pharmacy stores, under the brand names - Glucophage and Fortamet. It has been found that diabetic patients taking metformin are less likely to get cancer and have better outcomes if they do get cancer, as compared to those who do not take this drug.

Metformin can kill breast cancer stem cells that are responsible for the the spreading and occurrence of the dreaded disease, says Harvard researcher Kevin Struhl. In an experiment on mice carrying human breast cancer cells it was seen that standard chemotherapy was more effective when combined with metformin doses. Mice which were treated with this combination showed a cancer-free state for four months as compared with those treated with either drug alone.

"Although our studies were pretty much done on breast cancer cells, a lot of the principles are not specific just to breast cancer," Struhl said. "A lot of data shows lower cancer risk -- not just breast cancer -- in people taking metformin for diabetes."

Metformin is also one of the safest drugs. The good news is that it is a very well known compound and has a property that is selectively toxic to cancer stem cells.