PDE-5 inhibitor fails to prevent ED after radiation

Among men undergoing radiation therapy for prostate cancer, daily use of the phosphodiesterase type-5 inhibitor tadalafil (Cialis), compared with placebo, did not prevent loss of erectile function, a recently published study found.

The study, led by Thomas M. Pisansky, MD, of Mayo Clinic, Rochester, MN, and colleagues with the Radiation Therapy Oncology Group, appears in JAMA (2014; 311:1300-7).

Tadalafil is used to treat erectile dysfunction after prostate cancer treatment, but its role as a preventive agent has not been determined, according to the authors.

In the study, researchers 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%] or brachytherapy [37%]). 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% who received tadalafil retained erectile function compared with 74% who received placebo, an absolute difference of 5%. A significant difference between groups was also not observed at 1 year (72% vs 71%).

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 wrote.

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

The trial was conducted by the Radiation Therapy Oncology Group, which was supported by grants from the National Cancer Institute and by Eli Lilly & Co.

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