5α-reductase inhibitors and the risk of bladder cancer in a large, population-based cohort

PURPOSE

The ability of 5α-reductase inhibitors (5ARI) to reduce the risk of new onset bladder cancer (BC) has been studied with variable results. Our objective was to conduct a retrospective cohort population-based study to evaluate the association between 5ARI use, BC diagnosis, and BC mortality.

PATIENTS AND METHODS

We used routinely collected health care data from Ontario, Canada. Men ≥66 years of age with a prescription for a 5ARI were matched to non-5ARI users. Matching was done using a propensity score of selected covariates to make 96 different covariates comparable. We measured 5 additional baseline variables which may have impacted the risk of future BC diagnosis: prior cystoscopy, urine cytology, urinalysis, gross hematuria episodes, and transurethral resection of a bladder lesion. Only the first period of continuous usage of 5ARIs was considered. The prespecified at-risk period for outcomes started 1 year after initiating therapy and ended at the last date of 5ARI exposure + 1 year.

RESULTS

We identified 93,197 men who initiated 5ARI therapy (52% dutasteride, and 48% finasteride) between 2003 and 2013 and matched them 1:1 to men who did not start a 5ARI. The median at-risk period for the 5ARI group was 1.68 years (interquartile range 1.00, 4.27). With adjustment for the variables related to prior BC investigations there was no significant difference in BC diagnosis (hazard ratio [HR] 1.05, 95% confidence interval [CI] 0.82-1.32) during the period of 0 to <2 years of 5ARI use; however, after ≥2 years of 5ARI use, the risk of BC diagnosis was significantly lower among the 5ARI group (HR 0.82, 95% CI 0.79-0.94). In a similarly adjusted model, BC mortality was lower among 5ARI users, but no longer statistically significant (HR 0.82, 95% CI 0.65, 1.02). When stratified by type of 5ARI, finasteride significantly reduced the risk of BC diagnosis after ≥2 years of continuous use (HR 0.86, 95% CI 0.76, 0.96); however, dutasteride did not (HR 0.92, 95% CI 0.83, 1.03).

CONCLUSIONS

In a large cohort of men, the use of a 5ARI was associated with a significantly decreased the risk of BC diagnosis after more than 2 years of continuous therapy.

Clinical significance of 5-α reductase inhibitor and androgen deprivation therapy in bladder cancer incidence, recurrence, and survival: a meta-analysis and systemic review

PURPOSE

This study aimed to investigate the effect of androgen suppression therapy (AST), comprising a 5-α reductase inhibitor (5-ARi) and androgen deprivation therapy (ADT), on the risk of bladder cancer incidence, recurrence, and mortality.

MATERIALS AND METHODS

We used the PRISMA statement to report the methods and results of this meta-analysis. Bladder cancer incidence, recurrence, and mortality after 5-ARi treatment and ADT were assessed using risk ratios (RRs) and hazard ratios (HRs) with 95% confidence intervals (CIs). The protocol of this study is registered in the PROSPERO database (No. CRD42018118627).

RESULTS

We analyzed nine studies (n = 377,427) assessing the secondary effect of AST, with a mean follow-up period of 6 years (range, 2-13 years). Our result showed that the incidence of bladder cancer was significantly reduced when 5-ARi treatment (RR, 0.69; 95% CI, 0.58-0.81; I²=0%) and ADT (HR, 0.81; 95% CI, 0.70-0.94; I²=33%) were initiated before diagnosing bladder cancer. When treatment was initiated after diagnosing bladder cancer, 5-ARi treatment reduced cancer-specific mortality (RR, 0.29; 95% CI, 0.20-0.42; I²=4.1%), whereas ADT reduced bladder cancer recurrence (HR, 0.30; 95% CI, 0.19-0.49; I²=0%).

CONCLUSIONS

This study corroborates that the use of 5-ARi and ADT could be helpful in managing bladder cancer and should not be limited to prostatic abnormalities.