Reuters Health Information (2014-04-04): Tadalafil (Cialis) doesn't ward off ED from prostate cancer treatment


Tadalafil (Cialis) doesn't ward off ED from prostate cancer treatment

Last Updated: 2014-04-04 12:00:24 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Daily prophylactic use of the erectile dysfunction drug tadalafil (Cialis) did not preserve erectile function in men undergoing radiation therapy for prostate cancer in a randomized controlled trial.

About 40% of men report ED after radiation therapy and tadalafil is helpful in restoring erectile function when ED occurs after radiotherapy, but until now its role as a preventive agent hadn't been assessed in a controlled trial, Dr. Thomas M. Pisansky of the Mayo Clinic in Rochester, Minnesota, told Reuters Health by email.

The clearly negative result in the trial was not expected, Dr. Pisansky admitted.

"ED is thought to be due to blood vessel damage, and tadalafil may help improve blood vessel dysfunction. So, it made sense to see if tadalafil could prevent blood vessel damage and reduce the likelihood of developing ED after radiotherapy," he explained.

"All the 'stars were aligned' to indicate that this approach would be successful, so the lack of a demonstrable benefit was surprising," he said.

The study involved 242 men with normal erectile function scheduled for radiotherapy for prostate cancer. Half were assigned to 5 mg of tadalafil daily and half to placebo for 24 weeks starting with external radiotherapy (63%) or brachytherapy (37%).

There was no significant difference in the primary outcome of off-drug spontaneous erectile function at 28 to 30 weeks after the start of radiotherapy.

Among 221 evaluable men, 80 (79%) who took tadalafil retained erectile function at this point, as did 61 men (74%) who received placebo (p=0.49), an absolute difference of just 5%.

There was also no significant between-group difference in erectile function at one year, with 72% of men in the tadalafil group and 71% in the placebo group retaining erectile function (p=0.93). Tadalafil was not associated with significantly improved overall sexual function or satisfaction.

In a paper in JAMA April 2, the investigators conclude that "based on evidence available presently, there is no support for phosphodiesterase-5 inhibitor use to prevent ED after highly conformal external radiotherapy or low-dose-rate brachytherapy. Alternative strategies to prevent ED in this context appear warranted, perhaps with attention toward alternative dosing, investigation of neuroprotective interventions, or further refinements of radiotherapy delivery methods.

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


JAMA 2014;311:1300-1307.