Research presented Saturday in Chicago at the American Association for Cancer Research’s annual meeting revealed that popular diabetes medication metformin may slow prostate and other cancers.

Metformin has been under the microscope as a cancer cure since 2010, according to a Los Angeles Times story. In one of the first human trials, 22 men with prostate cancer were given 500mg of metformin three times a day for an average of 41 days before having their prostate removed. None of the participants had diabetes, nor did they report grade 3 adverse side effects on a scale of 1 (mild) to 5 (fatal). Biopsy samples were taken before and after prostate removal.

“This gave us the ability to compare what the prostate cancer looked like when it was first diagnosed to what it looked like when the prostate cancer was removed,” said medical oncologist Anthony M. Joshua of Princess Margaret Hospital, University Health Network, in Toronto, Canada. “We were able to directly measure the effect of metformin on the prostate cancer.”

A University of Texas study of 302 pancreatic cancer patients showed that 30 percent of participants given metformin were still alive after two years, compared with 15.4 percent who did not take the drug. Diabetes and pancreatic cancer often go hand-in-hand, according to HealthDay reporter Amanda Gardner. The Mayo Clinic’s website says the pancreas secretes insulin and other hormones to enable your body to process sugar.

Joshua says insulin fuels the growth of prostate cancer cells and that metformin, derived from a French lilac plant, may reduce the amount of insulin circulating in the blood. The drug reduced fasting glucose, body mass index, and waist-to-hip ratio in the prostate study participants.

Previous studies were conducted on mice. Metformin slowed growth of their liver tumors at the University of Maryland School of Medicine, reduced the number and size of oral cancer lesions at the U.S. National Institute of Dental and Craniofacial Research, and suppressed melanoma at Manchester, England’s Paterson Institute for Cancer Research. These findings were published in AACR journals on Saturday.

“There are very exciting clues from laboratory studies and population studies that metformin … may improve cancer outcomes or lower cancer risk,” said Dr. Michael Pollack, professor of oncology and of medicine and McGill University in Montreal. “However, we need more laboratory and clinical studies to find the best dose to use, to understand in what disease situations it may help most, and also to determine if metformin itself or a metformin derivative would be most suitable for trials.”