Finasteride Use and Risk of Bladder Cancer in a Multiethnic Population.

Purpose: Finasteride use has been associated with a reduced incidence of bladder cancer. However, the majority of studies have been conducted primarily in East Asian or White populations. Given differences in the incidence of bladder cancer among racial/ethnic groups, it is important to determine whether the effect of finasteride use on bladder cancer varies by race/ethnicity.

Materials And Methods: We identified all patients with a diagnosis of benign prostatic hyperplasia between 2000 and 2016 at our academic health center in Bronx, New York via an electronic medical record database. We then identified patients who were prescribed finasteride, and those who developed bladder cancer during followup. We used competing risk analysis to examine associations of finasteride use with risk of bladder cancer, adjusting for age, smoking and race/ethnicity.

Results: We identified 42,406 patients with benign prostatic hyperplasia (average±SD age 67±12.9 years), of whom 27.7% were Black and 14.8% were Hispanic. Finasteride was prescribed in 5,698 patients (13.4%). Bladder cancer was diagnosed in 84 of 5,698 finasteride users (1.5%), compared to 762 of 36,708 nonusers (2.1%, log-rank p=0.003). Finasteride was associated with a 36% reduction in risk of bladder cancer (HR: 0.64, 95% CI: 0.51-0.80; p <0.0001) among all patients. When data were stratified by race/ethnicity, finasteride use was associated with a reduction in risk of bladder cancer in White men (HR: 0.61, 95% CI: 0.43-0.86; p=0.005) and Hispanic men (HR: 0.44, 95% CI: 0.21-0.90; p=0.026), but there was no association among Black men (HR: 1.01, 95% CI: 0.67-1.51; p=0.964).

Conclusions: Our study corroborates previous findings that men who are on finasteride have a lower bladder cancer incidence. However, the reduction in risk was seen only in White and Hispanic men, but not among Black men. Therefore, race/ethnicity represents an important stratification factor for future larger studies on finasteride as chemoprevention for bladder cancer.