Older men who take testosterone replacement therapy for low testosterone levels do not appear to have a higher risk for prostate cancer than peers who do not take testosterone, according to a presentation at the annual meeting of the Endocrine Society.

Prostate cancer is a concern regarding testosterone therapy in older men, said lead author Aksam Yassin, MD, PhD, of the Clinic for Urology and Andrology of the Segeberger Clinics in Norderstedt, Germany.

"Testosterone treatment stimulates the growth of an existing prostate cancer, but there is no evidence that it causes this type of cancer," Yassin said.

The risk of prostate cancer and testosterone deficiency increases with age. Therefore, it is possible that a prostate cancer may occur in an older man during testosterone replacement therapy that is unrelated to treatment, Yassin said. His research, performed with scientists from Germany and the United Arab Emirates, aimed to determine if prostate cancer occurs more often with testosterone replacement therapy in men over 50 years of age.

The study involved 154 testosterone-deficient men (average age, 56 years) who had 1 to 3 years of follow-up testing. Patients received testosterone injections in a hospital clinic in Bremerhaven, Germany. Testosterone was a slow-release form called testosterone undecanoate (brand name Nebido) that is not yet available in the United States. The researchers compared these patients with 160 men visiting the clinic for a health checkup who had normal testosterone levels and did not receive testosterone treatment. Their average age was 58 years.

At baseline and then every 3 months afterward, all subjects had an evaluation that included a digital rectal exam, ultrasound measurement of prostate volume and a blood test for prostate-specific antigen. If a man's prostate-specific antigen level was over 4 micrograms per liter, he underwent a prostate biopsy.

The rectal exam found no abnormalities. Eleven men receiving testosterone had a biopsy, two of which showed a small cancerous tumor on one side of the prostate. A third man was found to have a high-grade prostate cancer that had not yet spread to other organs.

Of the 12 men in the untreated group, five had prostate cancer. Four tumors were on both sides of the prostate and were high grade. Not only was there not an excess of cancers in treated men, the authors noted that men receiving testosterone had smaller, less aggressive tumors.

"There is increasing evidence that testosterone replacement therapy in testosterone-deficient men can improve their symptoms, such as decreased bone and muscle mass and low sex drive and depression," Yassin said. "In view of the many benefits of treatment and the results of our study, we believe it is acceptably safe to treat older men with testosterone if there is a good reason for treatment."