Cheap diabetes drug metformin may fight cancer, studies show

(CBS News) Does hope for cancer treatment lie in new drugs? Not necessarily, as new research shows that a commonly prescribed diabetes drug, metformin, may help fight cancer.

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The drug helps diabetes patients keep their blood sugar in check and makes them more sensitive to insulin. But several new studies examined the effect of metformin on cancerous tumors, based on previous findings that metformin increases the activity of an enzyme involved in tumor suppression.

The latest findings were presented this month in the American Association for Cancer Research (AACR) meeting in Chicago.

Researchers studied the effect of metformin on patients affected with a variety of cancers, including melanoma, pancreatic, lung, and prostate cancer. The studies found metformin inhibits the growth of most tumor cells.

Pancreatic patients prescribed metformin had a 32 percent reduced risk for death compared to those not prescribed the drug, according to a study led by Dr. Dongui Li, professor at the University of Texas MD Anderson Cancer Center. Li and colleagues observed 302 patients with diabetes and pancreatic cancer- 117 of the patients were prescribed metformin.

Another study of melanoma patients, led by researchers at the Institute for Cancer Research in London, found that metformin alone contributed to the growth of cancerous tumors in mice - but when combined with other inhibitors, axitinib and bevacizumab, tumor growth was suppressed by up to 64 percent.

"Our results were surprising because combining metformin and vascular endothelial growth factor-A (VEGF-A) inhibitors was much more effective at blocking tumor growth than would be expected given the effect of either drug on its own," Dr. Richard Marais, professor of molecular oncology at The Paterson Institute for Cancer Research in Manchester, England, said in a written statement.

Another surprise about the drug? It's cheap and readily available. Since the U.S. patent on metformin expired in 2002, the drug has been available in inexpensive generic versions.

"We don't very often see [that] the generic drug that's available at your drugstore anyways might have some use for cancer," Dr. Michael Pollak, director of cancer prevention at McGill University in Montreal, told CNN. "It contrasts so much with what you hear in cancer research: doctors developing new targeted therapy that costs $800 a month, and it works a little bit - but only for certain kinds of patients with certain kinds of tumors."

The National Cancer Institute has more on cancer treatment.