Cialis Fails to Prevent Erectile Dysfunction From Prostate Cancer Treatment

Ball-and-stick model of tadalafil.

The drug tadalafil (Cialis) did not improve erectile function in men undergoing radiation therapy for prostate cancer. According to the authors of the study, the results don’t support the daily prophylactic use of tadalafil to prevent erectile dysfunction in prostate cancer patients. This is the first study to evaluate the role of tadalafil in men undergoing radiation therapy for prostate cancer.

The results were published in the Journal of the American Medical Association.

Erectile dysfunction is common following radiation therapy for prostate cancer. Tadalafil is one of the phosphodiesterase-5 inhibitors available that can help men in the general population who suffer from erectile dysfunction.

This trial was conducted to assess whether tadalafil would facilitate spontaneous erectile function in men treated with radiotherapy for prostate cancer.

The trial randomized 242 patients with full erectile function 1:1 to either placebo or 5 mg of tadalafil daily for 24 weeks starting at the time of their radiation therapy. All patients received either external radiation (63%) or brachytherapy (37%). Patients were recruited between November 2009 and February 2012 from 76 community-based and tertiary medical centers in the United States and Canada. The median age of the men was 63 years.

No significant difference was observed in erectile function between the experimental group and the placebo group. Among the 221 evaluable patients in the trial, 79% (80 patients) retained erectile function between weeks 28 and 30 after treatment compared with 74% (61 patients) who received placebo (P = .49). No significant difference was observed at 1 year after therapy (72% vs 71%; P = .93).

Daily treatment with tadalafil was not linked with improved sexual satisfaction: Partners of men taking tadalafil did not note significant effects.

Previous placebo-controlled studies with phosphodiesterase-5 inhibitors sildenafil and vardenafil in patients being treated with radiation therapy or surgery showed either benefit or no benefit. According to Thomas M. Pisansky, MD, of the Mayo Clinic in Rochester, Minnesota, and coauthors, these agents function intermittently in contrast to tadalafil, which functions continuously. The studies with sildenafil and vardenafil were smaller patient studies.

Based on the current study and previous studies with other phosphodiesterase-5 inhibitors, “there is no support for phosphodiesterase-5 inhibitor use to prevent ED after highly conformal external radiotherapy or low-dose-rate brachytherapy,” the authors concluded.

“Alternative strategies to prevent erectile dysfunction in this context appear warranted, perhaps with attention toward alternative dosing, investigation of neuroprotective interventions, or further refinements of radiotherapy delivery methods,” added the authors.

The tadalafil trial was funded by both the National Cancer Institute and Eli Lilly and Company, the manufacturer of the drug.