Association of 5α-Reductase Inhibitors With Prostate Cancer Mortality

• There is evidence that 5α-reductase inhibitors (5-ARIs), a standard treatment of benign prostate hyperplasia, are associated with a decrease in the incidence of prostate cancer (PCa). However, studies to date have had conflicting results regarding the association with prostate cancer mortality (PCM).ObjectiveTo evaluate the association of treatment with 5-ARIs with PCM in men without a prior diagnosis of PCa.Design, Setting, and ParticipantsThis population-based cohort study was conducted in Stockholm, Sweden, between January 1, 2007, and December 31, 2018, and included 429 977 men with a prostate-specific antigen (PSA) test within the study period. Study entry was set to 1 year after the first PSA test. Data were analyzed from September 2021 to December 2021.ExposuresAfter their initial PSA test, men with 2 or more newly dispensed prescriptions of 5-ARI, finasteride, or dutasteride were considered 5-ARI users (n = 26 190).Main Outcomes and MeasuresPrimary outcome was PCM. Cox proportional hazards regression models were used to calculate multivariable-adjusted hazard ratios (HRs) and 95% CIs for all-cause mortality and PCM.ResultsThe study cohort included 349 152 men. The median (IQR) age for those with 2 or more filled prescriptions of 5-ARI was 66 (61-73) years and 57 (50-64) years for those without. The median follow-up time was 8.2 (IQR, 4.9-10) years with 2 257 619 person-years for the unexposed group and 124 008 person-years for the exposed group. The median exposure to treatment with 5-ARI was 4.5 (IQR, 2.1-7.4) years. During follow-up, 35 767 men (8.3%) died, with 852 deaths associated with PCa. The adjusted multivariable survival analysis showed a lower risk of PCM in the 5-ARI group with longer exposure times (0.1-2.0 years: adjusted HR, 0.89; 95% CI, 0.64-1.25; >8 years: adjusted HR, 0.44; 95% CI, 0.27-0.74). No statistically significant differences were seen in all-cause mortality between the exposed and unexposed group. Men treated with 5-ARIs underwent more PSA tests and biopsies per year than the unexposed group (median of 0.63 vs 0.33 and 0.22 vs 0.12, respectively).Conclusions and RelevanceThe results of this cohort study suggest that there was no association between treatment with 5-ARI and increased PCM in a large population-based cohort of men without a previous PCa diagnosis. Additionally, a time-dependent association was seen with decreased risk of PCM with longer 5-ARI treatment. Further research is needed to determine whether the differences are because of intrinsic drug effects or PCa testing differences.

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