Efficacy and Safety of Tadalafil 20 mg on Demand vs. Tadalafil 5 mg Once-a-Day in the Treatment of Post-Radiotherapy Erectile Dysfunction in Prostate Cancer Men: A Randomized Phase II Trial

Abstract

The role of phosphodiesterase type 5 inhibitors in the treatment of post-radiotherapy erectile dysfunction (ED) has not been extensively investigated. To compare the efficacy and safety of on-demand 20-mg tadalafil (arm A) with the newly released tadalafil 5-mg once-a-day dosing (arm B) in patients with ED following radiotherapy for prostate cancer (PC). Randomized study to receive on-demand 20-mg or once-a-day 5-mg tadalafil for 12 weeks. Main Outcome Measures. Changes in the International Index of Erectile Function (IIEF) domain scores and Sexual Encounter Profile (SEP) question 2 and 3 positive response rates. Fifty-two out of 86 screened patients were randomized. Forty-four patients were evaluable for efficacy. A significant improvement in all domains of the IIEF was observed in both arms (P = 0.0001) with mean erectile function domain scores values of 25 and 27.1 for the 20-mg and 5-mg tadalafil, respectively (P = 0.19). SEP 2 and 3 positive response rates increased from 0% in both arms at baseline to 81% and 70% in the 20-mg arm and 90% and 73% in the 5-mg arm, respectively, at the end of treatment (P = 0.27). End of treatment global efficacy question positive answers were 86% in the 20-mg arm and 95% in the 5-mg arm (P = 0.27). Higher treatment compliance was shown in arm B (100%) as compared with arm A (86%). There was a nonstatistically significant trend toward fewer side effects in favor of the 5-mg daily dose arm. In the study population, both tadalafil formulations generated significantly high response rates according to the outcome measures and were well tolerated. The once-a-day 5-mg dosing showed higher compliance and marginally reduced side effects, thus making it an attractive alternative to on-demand therapy for ED in post-radiotherapy PC patients.