Diabetes drug metformin may double as cancer-fighting medicine Metformin is a workhorse drug for people with diabetes. It helps patients control their blood sugar and makes them more sensitive to insulin. But soon, metformin may take on a new role fighting cancer. Results of a preliminary study presented Saturday at the American Assn. for Cancer Research's annual meeting in Chicago suggest metformin slowed the growth of prostate cancer tumors. The study involved 22 men with prostate cancer. All of them were scheduled to have their prostates removed, and some of them took metformin for about seven weeks beforehand. After the prostates were excised, researchers from Toronto compared them and found that tumors grew more slowly in men who took the diabetes drug than in men who didn't. Those findings were augmented by a flurry of studies published Saturday in various AACR journals. Taken together, they offer hopeful signs that the diabetes drug may help prevent or treat an array of cancers. In a study that examined 302 patients with pancreatic cancer, 117 were taking metformin. Researchers from the University of Texas M.D. Anderson Cancer Center found that the one-year survival rate for patients on metformin was 64%, compared with only 46% for patients who weren't on the drug. After two years, the survival rate was 30% for those taking metformin and 15% for those who weren't. The findings were published in Clinical Cancer Research. Liver cancer tumors grew less in mice that were given metformin than in mice that didn't get the drug. University of Maryland School of Medicine researchers found that metformin's ability to prevent the formation of fat in the liver helped keep the cancer at bay. The study was published in Cancer Prevention Research. In another mouse study, researchers from the National Institute of Dental and Craniofacial Research induced the animals to grow pre-cancerous lesions in their mouths. Mice who took metformin wound up with fewer oral cancers, and the tumors that did grow were smaller. These results also appear in Cancer Prevention Research. Metformin is derived from the French lilac plant, Galega officinalis. According to this report in the journal Practical Diabetes, it is "reputed to be the most widely prescribed agent in the treatment of diabetes." Researchers have been on to metformin's potential as a cancer treatment since at least 2010, according to this Los Angeles Times story. Return to the Booster Shots blog.