The Long-Term Impact of 5-alpha Reductase Inhibitors on the Development of Bladder Cancer and the Need for Radical Cystectomy: A Nationwide Observational Study.

Purpose: To investigate the long-term effects of taking 5-alpha reductase inhibitors (5ARIs) on the development of bladder cancer (BC) and the implementation of radical cystectomy (RC), a standard procedure for advanced BC.

Materials and methods: From the National Health Insurance Sharing Service database, males aged over 40 years who underwent serum prostate-specific antigen testing from 2006 through 2017 were identified, which is required for the prescription of 5ARIs. The association between the administration duration of 5ARIs and the practice for BC was analyzed.

Results: Of the 3,843,968 subjects, 1,514,713 (39.4%) took 5ARIs for an average of 1.53 years, remaining 2,329,255 (60.6%) as non-5ARI counterparts. The incidence of BC was higher in the non-5ARI than in the 5ARI group (1.25% vs. 0.87%, p<0.001), as was the implementation rate of RC (11.1% vs. 10.4%, p=0.037). In a multivariate analysis, the non-5ARI group had a significant risk of BC (hazard ratio [HR]=2.289, 95% confidence interval [CI]=2.241-2.338) and RC (HR=2.199, 95% CI=2.061-2.348) than the 5ARI group. Among the 5ARIs group, though the incidence of BC was maintained (slope=-0.002 per year, p=0.79) after an initial increase for two years, the rate of RC decreased (slope=-1.1, p<0.001) consistently for ten years during the administration.

Conclusions: Compared to the untreated group, 5ARIs use was associated with lower rates of BC and RC. In contrast to the increase in BC seen with short-term use of less than two years, long-term use of 5ARIs decreased the rate of RC in a duration-dependent manner for ten years, suggesting a strategy to prevent disease progression.