Medication does not help prevent ED following radiation therapy for prostate cancer

Among men undergoing radiation therapy for prostate cancer, daily use of the erectile dysfunction drug tadalafil, compared with placebo, did not prevent loss of erectile function, according to a study in the April 2 issue of JAMA.

Erectile dysfunction (ED) is a common condition resulting from many causes, including prostate cancer treatment. An estimated 40 percent of men report ED after radiation therapy, and half of all men use erectile aids following this therapy. Tadalafil is used to treat erectile dysfunction after prostate cancer treatment, but its role as a preventive agent has not been determined, according to background information in the article.

Thomas M. Pisansky, M.D., of the Mayo Clinic, Rochester, Minn., and colleagues with the Radiation Therapy Oncology Group, randomly assigned 242 men with prostate cancer to receive tadalafil (5 mg) or placebo daily for 24 weeks starting with radiation therapy (either with external radiotherapy [63 percent] or brachytherapy [37 percent]). The study was conducted at 76 sites in the United States and Canada; participants were recruited between November 2009 and February 2012, with follow-up through March 2013.

Between weeks 28 and 30 after the start of radiation therapy, among evaluable participants, 79 percent who received tadalafil retained erectile function compared with 74 percent who received placebo, an absolute difference of 5 percent. A significant difference between groups was also not observed at 1 year (72 percent vs 71 percent). Tadalafil was not associated with improved overall sexual function or satisfaction, and partners of men assigned tadalafil noted no significant effect on sexual satisfaction.

"These findings do not support the scheduled once-daily use of tadalafil to prevent ED in men undergoing radiotherapy for localized prostate cancer," the authors write.

They add that alternative strategies to prevent ED in this context appear warranted, including different dosing or further refinements of radiation therapy delivery methods.