SAN DIEGO – Testosterone replacement therapy is not associated with an increased risk of cancer or prostate cancer in men, based on results from a large study with a mean follow-up of nearly 9 years.
"We had hoped for these results," Dr. Michael L. Eisenberg said in an interview during a poster session at the annual meeting of the American Urological Association. "Certainly people are worried about testosterone in terms of prostate cancer development."
In a study conducted during his fellowship training in male reproductive medicine and microsurgery at Baylor College of Medicine, Houston, Dr. Eisenberg and his associates queried their database for all men with a serum testosterone level and then examined charts to determine testosterone replacement therapy (TRT) status. They limited their analysis to 750 men who lived in Texas and then linked the patient records to the Texas Cancer Registry to determine the incidence of cancer. Time at risk was measured from the date initiating TRT or from the first office visit for men not on TRT.
Of the 750 men, 333 (44%) were on TRT and 417 (56%) were not, reported Dr. Eisenberg, who is now director of male reproductive medicine and surgery at Stanford (Calif.) University Medical Center. Their mean age at study entry was 47 years, and they were followed for a mean of 8.7 years. Baseline testosterone levels were significantly lower in men on TRT compared with those who were not (a mean of 346 vs. 369 ng/dL, respectively; P less than 0.01).
Overall, 55 men developed cancer during the study period, including 22 men on TRT (6.6%) and 33 who were not on TRT (7.9%). When the researchers adjusted for age and year of evaluation, they found no significant difference in the risk of cancer based on TRT use (hazard ratio, 0.97).
Compared with the general Texas population, men on TRT had an age-adjusted standardized cancer incidence rate (SIR) of 1.5 while those not on TRT had a SIR of 1.7. When the researchers examined prostate cancer alone, they found that men on TRT had an age-adjusted SIR of 2.6 while those not on TRT had a SIR of 3.7. That particular finding is "very preliminary, but maybe there’s some possible protective effect of testosterone," said Dr. Eisenberg, who is also an assistant professor of urology at Stanford.
The study was funded by Endo Pharmaceuticals. Dr. Eisenberg said he had no relevant financial conflicts to disclose.