A Randomized, Double-Blind, Placebo-Controlled, Cross-Over Study To Assess The Efficacy Of Tadalafil (Cialis®) In The Treatment Of Erectile Dysfunction After External-Beam Radiotherapy For Prostatic Cancer

358 patients who completed radiotherapy at least 12 months prior to the study were approached by mail.  Sixty patients were included and entered a double-blind, placebo-controlled, cross-over study lasting 12 weeks. They received 20 mg of tadalafil or placebo for 6 weeks. Drug or placebo was taken on demand at patient’s discretion, with no restrictions regarding the consumption of alcohol or food, at least once a week and no more than once daily. At 6 weeks patients crossed over to the alternative treatment. Data were collected using the Sexual Encounter Profile and the International Index of Erectile Function (IIEF) questionnaires. Side-effects were also recorded. Comparison between tadalafil scores and placebo scores was done using Wilcoxon’s matched pairs test. For within- and between-group comparison of percentages, McNemar’s test and Fisher’s exact test were used, respectively. Results: Mean age at study entry was 69 years. All patients completed the study. There was a significant increase in mean scores from baseline with tadalafil, but not with placebo. For all the IIEF domains there was a statistically significant difference between tadalafil and placebo. Sixty-seven percent of the patients reported an improvement of erectile function with tadalafil (placebo: 20%) and 48% reported successful intercourse with tadalafil (placebo: 9%). Side effects were mild or moderate. Except for headache, flushing and dyspepsia, all other reported adverse events did not differ significantly between the two treatments. Conclusions: Tadalafil is an effective treatment for erectile dysfunction after EBRT for prostatic cancer with successful intercourse reported in almost 50% of the patients, and is well tolerated.