Chicago ? A drug already sold for other prostate problems significantly cut the chances of prostate cancer being found in men with an increased risk of the disease, doctors reported Monday.

In a large international study, dutasteride, sold as Avodart, lowered the chances of a prostate cancer diagnosis by 23 percent after four years of use.

Tens of thousands of men each year face a problem like those in the study: worrisome results from prostate cancer screening tests and biopsies that come back negative.

“There’s no question” that many had small tumors that were not detected, yet the drug still lowered the risk of cancer being found years later, said Dr. Gerald Andriole of Washington University School of Medicine in St. Louis.

He led the study in the United States and reported results Monday at an American Urological Association conference in Chicago. The study was sponsored by Avodart’s maker, British-based GlaxoSmithKline PLC, and Andriole has consulted for the company.

Dutasteride now joins finasteride, sold as Merck & Co. Inc.’s Proscar and in generic form, as a potential prostate cancer prevention drug. In February, health experts recommended that men consider these medicines if they are regularly getting screened for the disease.