A common diabetes drug may prevent cancer

There's growing evidence that metformin, a drug commonly prescribed for diabetes, may also help prevent some cancers. Researchers reported this week that it hold promise as a way to keep smokers from developing lung cancer.

Metformin has been shown to switch on an enzyme that blocks mTOR -- a protein that helps tobacco-induced lung tumors grow.

They said metformin prevented lung tumor growth in mice exposed to a cancer-causing agent found in tobacco smoke, and because it is already widely used in people, it may be worth further study.

"Although smoking cessation is the most important step for current smokers, over half of lung cancer cases are diagnosed in former smokers, raising the importance of identifying those at highest risk and identifying effective preventive treatments," said Dr. Philip Dennis of the National Cancer Institute, part of the National Institutes of Health. The findings were so strong the team now wants to test it in smokers to see if it can keep then from developing tumors.

Other studies have shown that metformin can cut diabetics' risk of pancreatic and breast cancers, and it has also been investigated for a role in preventing prostate cancer.

The problem with all these studies is that metformin is now a generic drug, so there is no incentive for pharmaceutical companies to launch an expensive clinical trial to demonstrate the drug's utility when they would not be the exclusive beneficiary of their findings.


"Among the various treatment options for Type 2 diabetes, if all other things are equal, early evidence that metformin might have benefit on the oncology side may play a role in decision making," said Dr. Michael Pollak, a medical oncologist at McGill University in Montreal, who surveyed recent metformin research in an article in the journal Cancer Prevention Research.