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 5α‐reductase inhibitors (5 ARI s) and α‐blockers among men with benign prostatic hyperplasia ( BPH ) in relation to prostate cancer ( PC a) 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 PC a diagnosis, metastatic PC a, Gleason score 8–10 PC a, and PC a mortality among 5 ARI users ( n = 4 571), α‐blocker users ( n = 7 764) and non‐users ( n = 11 677). Results In comparison with both non‐users and α‐blocker users, 5 ARI users had a ~40% lower risk of a PC a diagnosis (11.0% and 11.4% vs 5.8%, respectively), and α‐blocker users had an 11% lower risk of a PC a diagnosis compared with non‐users. Overall, the incidence of metastatic PC a and PC a mortality was not significantly different among 5 ARI or α‐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 ~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 5 ARI s was associated with lower risk of PC a diagnosis, regardless of comparison group. Risk of high grade PC a was higher among both 5 ARI users and α‐blocker users compared with non‐users; however, this did not translate into higher risk of PC a mortality.