Objective To report penile integrity measures, including stretched penile length (SPL), from a randomized, double-blind, double-dummy, placebo-controlled trial evaluating treatment with tadalafil initiated after nerve-sparing radical prostatectomy (nsRP). Methods Patients aged ≤68 years were randomized after nsRP 1:1:1 to 9-month double-blind treatment (DBT) with tadalafil 5 mg once daily (OaD), 20-mg tadalafil on-demand ("pro-re-nata"; PRN), or placebo, followed by 6-week drug-free washout and 3-month open-label OaD treatment. Secondary outcome measures included the change in SPL from pre-nsRP to the end of DBT (analysis of covariance adjusting for treatment, country, baseline, age, and nerve-sparing score), responses to Sexual Encounter Profile (SEP) questions 1-3 (mixed models for repeated measures adjusting for treatment, country, visit, visit-treatment-interaction, age), and Standardized Morning Erection Question (Cochran-Mantel-Haenszel test adjusted for age and country). Results Four hundred twenty-three patients were randomized to tadalafil OaD (N = 139), tadalafil PRN (N = 143), and placebo (N = 141). Greater retainment of SPL was observed with tadalafil OaD vs placebo at the end of DBT (least-square mean [95% confidence interval] difference OaD vs placebo, 4.1 mm [0.4 to 7.8 mm]; P =.032). No significant effects on SPL were found for tadalafil PRN vs placebo, or for the nerve-sparing score. Penile tumescence (SEP1) and ability for vaginal insertion (SEP2) significantly improved vs placebo at the end of double-blind and open-label treatment for patients randomized to tadalafil OaD only. The ability for successful sexual intercourse (SEP3) significantly improved with tadalafil OaD vs placebo only during DBT. The distribution of Standardized Morning Erection Question responses was different at the end of DBT (P =.045); 34.2% of patients on tadalafil OaD, 50.0% on tadalafil PRN, and 56.5% on placebo reported absence of morning erections. Conclusion These data suggest the early initiation of tadalafil OaD protects from penile length loss and may contribute to protection from structural cavernosal changes after nsRP.
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