Men who take finasteride to reduce prostate size or promote hair growth are less likely to be diagnosed with bladder cancer than men who do not use the medication, according to recent novel findings.

A team led by Michael A. Liss, MD, of the University of Texas Health Science Center at San Antonio, analyzed data from 72,370 men who participated in the Prostate, Lung, Colorectal, and Ovarian (PLCO) cancer screening trial and met the researchers’ study inclusion criteria. Of these, 6,069 (8.4%) reported using finasteride. Bladder cancer was diagnosed in 65 (1.07%) of the 6,069 finasteride versus 966 (1.46%) of the 66,301 of those who reported no use of finasteride during the trial, Dr. Liss and his colleagues reported in European Urology (2016;69:407-410). In analyses that controlled for age and smoking, self-reported finasteride use was associated with a significant 37% decreased risk of bladder cancer.

Preclinical models have suggested a potential beneficial effect of finasteride on bladder cancer development, but the findings are the first from a large-scale trial to demonstrate a possible preventive or therapeutic role of finasteride for bladder cancer, the authors stated.

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Dr. Liss’ group acknowledged that their study was limited by its observational design, the lack of available data on many confounding variables for bladder cancer, such as alcohol use, and the reliance on annual self-reported use of finasteride, which is subject to missing values and error.

The authors pointed out that finasteride use may have reduced lower urinary tract symptoms and/or microscopic hematuria and thus decreased the rate of cystoscopy.

In an accompanying editorial (pp.411-412), Carlo La Vecchia, MD, of the University of Milan in Italy, noted that the new study is the first, to his knowledge, to examine the association between finasteride and bladder in humans. “Repetition of its findings using either a case-control approach including an adequate number of relevant covariates or, more likely, a record-linage approach with large regional or national administrative databases … is required to confirm the inverse association between finasteride and bladder cancer. Such an inverse association could have major clinical and public health relvance,” Dr. La Vecchia wrote.