Background: The Prostate Cancer Prevention Trial (PCPT) was a randomized, double-blind, placebo-controlled study of the efficacy of finasteride in preventing prostate cancer in 18,882 men aged 55 years or older. The PCPT offered an opportunity to prospectively study the effects of finasteride and other covariates on sexual dysfunction.
Methods: We assessed sexual dysfunction in 17,313 PCPT participants during a 7-year period. A battery of questionnaires assessed sexual dysfunction (Sexual Activity Scale score); age; race; SF-36 Mental Health Inventory-5, Physical Function, and Vitality scores; body mass index; smoking status; and the presence of diabetes and hypertension. Assessments began at month 6 after random assignment and included the Sexual Activity Scale score at randomization as a covariate. Two-sided general t tests, with a cutoff of P value less than .05, were used to determine the statistical significance for mixed model effects with correlated random time slopes and intercepts. The changing impact of covariates on sexual dysfunction was also assessed at 6 months, 3.5 years, and 6.5 years after randomization.
Results: Finasteride increased sexual dysfunction only slightly and its impact diminished over time; the increase in the Sexual Activity Scale score relative to placebo of 3.21 points (95% confidence interval [CI] = 2.83 to 3.59 points; P<.001) at the first assessment decreased to 2.11 points (95% CI = 1.44 to 2.81 points; P<.001) at the end of study. These Sexual Activity score values were small on a scale of 0-100, the range observed in the study, and in comparison with individual variation. After adjustment for all covariates, mean sexual dysfunction increased in both arms from baseline (6 months after randomization) by 1.26 Sexual Activity points (95% CI = 1.16 to 1.36 points; P<.001) per year, corresponding to a cumulative increase of 8.22 points (95% CI = 7.52 to 8.92 points; P<.001) over the study period.
Conclusions: The effect of finasteride on sexual functioning is minimal for most men and should not impact the decision to prescribe or take finasteride.