Impact of 5α-reductase inhibitor and α-blocker therapy for benign prostatic hyperplasia on prostate cancer incidence and mortality

Objective To investigate the use of 5 alpha-reductase inhibitors (5ARIs) and alpha-blockers among men with benign prostatic hyperplasia (BPH) in relation to prostate cancer (PCa) incidence, severity and mortality. Patients and Methods A retrospective 20-year cohort study in men residing in Saskatchewan, aged 40-89 years, with a BPH-coded medical claim between 1995 and 2014, was conducted. Cox proportional hazards regression was used to compare incidence of PCa diagnosis, metastatic PCa, Gleason score 8-10 PCa, and PCa mortality among 5ARI users (n = 4 571), alpha-blocker users (n = 7 764) and non-users (n = 11 677). Results In comparison with both non-users and alpha-blocker users, 5ARI users had a similar to 40% lower risk of a PCa diagnosis (11.0% and 11.4% vs 5.8%, respectively), and alpha-blocker users had an 11% lower risk of a PCa diagnosis compared with non-users. Overall, the incidence of metastatic PCa and PCa mortality was not significantly different among 5ARI or alpha-blocker users compared with non-users (adjusted hazard ratios [HR] of metastatic PCa: 1.12 and 1.13, respectively, and PCa mortality: 1.11 and 1.18, respectively, P > 0.05 for both drugs), but both 5ARI and a-blocker users had similar to 30% higher risk of Gleason score 8-10 cancer, adjusted HR 1.37, 95% confidence interval [CI] 1.03-1.82, P = 0.03, and adjusted HR 1.28, 95% CI 1.03-1.59, P = 0.02, respectively compared with non-users. Conclusion The use of 5ARIs was associated with lower risk of PCa diagnosis, regardless of comparison group. Risk of high grade PCa was higher among both 5ARI users and alpha-blocker users compared with non-users; however, this did not translate into higher risk of PCa mortality.