New research claims Testosterone therapy may be safe for men with prostate cancer.

Doctors have long held that men with prostate cancer should not be given testosterone because the hormone might fuel tumor growth. But a small study adds to evidence that the fear may be overblown, at least in patients without evidence of recurrent or metastatic disease.

Researchers studied 13 men with scores of 6 or 7 on the 10-point Gleason scale, indicating mildly to moderately aggressive prostate cancer. They all initially chose watchful waiting rather than treatment for their cancers. All the men had low testosterone.

The men received testosterone therapy for an average of two and a half years, and had periodic prostate biopsies. None of their cancers progressed or spread to other organs. One subject whose score had increased to 7 from 6 had his prostate removed, but the final pathological exam found no aggressive disease.

The authors acknowledge that the study, published in the April issue The Journal of Urology, was small and retrospective. Still, it is the first to use biopsies to monitor the effects of testosterone in men with untreated, localized prostate cancer.

The lead author, Dr. Abraham Morgentaler, an associate clinical professor of surgery at Harvard, said that the findings of this and other recent studies suggest that the risks of testosterone therapy may have been exaggerated.