"This is the first epidemiological study of metformin in the cancer population, and it offers an exciting direction for future chemoprevention research for a disease greatly in need of both treatment and prevention strategies," said Donghui Li, Ph.D., professor in M. D. Anderson's Department of Gastrointestinal Medical Oncology.

"Metformin works by increasing the cellular sensitivity to insulin and decreasing its level circulating in diabetics. Insulin also seems to have a growth-promoting effect in cancer," said Li, the study's senior author. "Metformin activates the AMP kinase, which is a cellular energy sensor. Recent publications have described that AMP kinase also plays an important role in the development of cancer by controlling cell division and growth."