Daily use of tadalafil (Cialis) did not improve erectile function compared to placebo or prevent erectile dysfunction among men undergoing radiotherapy for prostate cancer, according to results of a stratified, placebo-controlled, double-blind, parallel-group study with 1:1 randomization at 76 community-based tertiary medical sites in the United States and Canada.
“These findings do not support daily use of tadalafil to prevent erectile dysfunction in these patients,” Thomas M. Pisansky, MD, of Mayo Clinic, Rochester, Minnesota, and coauthors wrote in the Journal of the American Medical Association.
Patients with clinical stage II (T1b-T2b, N0, M0) prostate adenocarcinoma and intact erectile function were assigned 5 mg of tadalafil daily or placebo for 24 weeks, starting within 7 days after the initiation of external radiotherapy (63%) or brachytherapy (37%). All participants were ≥ 18 years old with a Gleason score < 7 and a serum prostate-specific antigen (PSA) level < 20 ng/mL, or a Gleason score ≥ 7 and a PSA < 15 ng/mL.
“The primary end point was to determine whether tadalafil maintained spontaneous erections between weeks 28 and 30 after the start of radiotherapy, which was 4 to 6 weeks after tadalafil was stopped,” the investigators explained. “Among 221 evaluable participants, 80 [79%; 95% CI = 70%–88%] assigned to receive tadalafil retained erectile function between weeks 28 and 30 compared with 61 [74%; 95% CI = 63%–85%] assigned to receive placebo (P = .49)—an absolute difference of 5% (95% CI = −9% to 19%). A significant difference was also not observed at 1 year [72%; 95% CI = 60%–84% vs 71%; 95% CI = 59%–84%; P = .93],” the investigators reported. “Tadalafil was not associated with significantly improved overall sexual function or satisfaction,” the authors added, and the “partners of men assigned tadalafil noted no significant effect on sexual satisfaction.”
Grade 1 to 2 adverse effects attributed to treatment (tadalafil or radiotherapy) were reported by 65 patients (59%) in the tadalafil group and 56 patients (52%) in the placebo group. Severe or life-threatening adverse events were observed in 3% of patients in the tadalafil group and 1% in the placebo group.
The U.S. Food and Drug Administration approved prescribing 2.5 or 5 mg of tadalafil daily, the authors noted. They added:
Selection of 5 mg of tadalafil once daily in this study was well supported by its efficacy profile, its performance relative to other phosphodiesterase-5 inhibitor medications, and its pharmacological properties and mechanism of action. Despite the soundness of preliminary investigations, we found no benefit to tadalafil as an [erectile dysfunction] prevention agent after radiotherapy, with not even the slightest suggestion in this regard. ■
Pisansky TM, et al: JAMA 311:1300-1307, 2014.