Prostate cancer developed in 20 men within months to a few years after they began testosterone supplementation to correct a deficiency of the hormone, investigators report.

"There are several anecdotal case reports, small studies, and observational studies like ours which raise concern but do not provide conclusive evidence yet," Dr. Franklin D. Gaylis told Reuters Health.

The issue is a concern because prostate cancer is usually driven by testosterone.

Gaylis, from the University of California at San Diego Medical Center, and colleagues report this series of patients "in whom clinically significant prostate cancer developed and was presumed to be related to exogenous testosterone use," in the Journal of Urology.

The men were identified in six different urology practices. Prostate cancer was detected within 2 years of the start of testosterone replacement in 11 of these men, seven of them within the first year, the authors report. The others were diagnosed after 28 months to 8 years.

Eleven men had normal prostate exams before testosterone supplementation was begun, the report indicates, and the average PSA level of the 17 men tested before treatment was 3, although the range was 0.9 to 15. The threshold for further evaluation is usually 4.

A 'shot across the bow'

"It is our belief that men, especially those with a family history of prostate cancer, should not receive a prescription for testosterone supplementation without careful, informed consultation regarding the risks and benefits of such treatment," the investigators conclude.

"I would hope that guidelines would be developed by experts in the field to help us appropriately and carefully prescribe testosterone replacement to men who clearly need it and who would benefit from it, and then monitor them for potential adverse outcomes, e.g., the development of prostate cancer," Gaylis said.