Use of the diabetes drug metformin is associated with a decreased risk of a prostate cancer (PCa) diagnosis, new findings suggest.

In a study of 12,226 men diagnosed with PCa and 122,260 population controls, Mark A. Preston, MD, of Massachusetts General Hospital in Boston, and colleagues found that men who used metformin had a significant 16% decreased risk of a PCa diagnosis in adjusted analyses compared with non-users. Among men who had undergone PSA testing in the previous year, metformin use was associated with a significant 34% decreased risk of a PCa diagnosis.

Diabetics on no medication or on other oral hypoglycemic agents did have a significant decrease in the risk of a PCa diagnosis, the researchers reported online ahead of print in European Urology.

The researchers identified study subjects using the Danish Cancer Registry and the Aarhus University Prescription Database.

In a previous Canadian study of older diabetic men published in the Journal of the National Cancer Institute (2013;105:1123-1131), researchers found no association between metformin use and PCa risk. The study included 5,306 PCa case subjects and 26,530 matched controls. A meta-analysis published in Cancer Epidemiology (2013;37:207-218) found that metformin can reduce the incidence of a number of cancers, but had no effect on PCa incidence.