Preclinical evidence suggests that 5-alpha reductase inhibitors, commonly used to treat benign prostatic hyperplasia, are associated with reduced incidence of certain urological cancers, yet epidemiological studies are conflicting. This study aimed to determine whether 5-alpha reductase inhibitors are associated with a reduced risk of kidney and bladder cancers.

We conducted a new user active-comparator cohort study in the United Kingdom Clinical Practice Research Datalink. From a base cohort of patients with incident benign prostatic hyperplasia, new users of 5-alpha reductase inhibitors and alpha-blockers were identified. Patients were followed-up until a first ever diagnosis of kidney or bladder cancer, death from any cause, end of registration, or 31st December 2017. Cox proportional hazards models were used to calculate hazard ratios and 95% confidence intervals for incident kidney and bladder cancer.

There were 5,414 and 37,681 new users of 5-alpha reductase inhibitors and alpha-blockers, respectively. During a mean follow-up of 6.3 years, we found no association between the use of 5-alpha reductase inhibitors and kidney (adjusted hazard ratio: 1.26, 95% CI 0.74-2.12, n=23) or bladder (adjusted hazard ratio: 0.89, 95% CI 0.64-1.23, n=57) cancer risk compared to alpha-blockers. Similar results were observed across sensitivity analyses.

In this study, we found no association between the use of 5-alpha reductase inhibitors and kidney or bladder cancer incidence in men with benign prostatic hyperplasia when compared to alpha-blocker use.

The findings of this study indicate that 5-alpha reductase inhibitors are unlikely to reduce kidney or bladder cancer risk.