Men who take a phosphodiesterase type 5 inhibitor (PDE5i) do not appear to have a reduced risk of prostate cancer (PCa), a new study finds.

“In vitro mouse studies have suggested that these drugs might have some anticancer activity, but the evidence in human subjects is mixed,” lead investigator Stephen J. Freedland, MD, of Cedars-Sinai Medical Center in Los Angeles, stated in a press release. “Given the routine use of PDE-5i and the possibility that these agents may have anticancer activity, we wanted to test the association between their use and risk of developing prostate cancer.”

Dr Freedland and colleagues conducted a post-hoc analysis of the Reduction by Dutasteride of Prostate Cancer Events (REDUCE) trial, a multicenter, randomized trial comparing daily dutasteride with placebo in men with benign prostatic hyperplasia. Of 6501 mostly white men with PSA levels of 2.5 to 10.0 ng/mL and negative prostate biopsy at baseline, 364 were taking a PDE5i, including tadalafil, sildenafil, and vardenafil. REDUCE participants then underwent repeat transrectal ultrasound-guided biopsies at 2 and 4 years.

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Results published online ahead of print in the Journal of Urology showed that PDE5i use was not associated with PCa diagnosis. PCa developed in about a fifth of PDE5i users and nonusers. The ED drugs also did not influence development of low-grade or high-grade disease, whether the Gleason score cutpoint was 7 or 8. The investigators adjusted for baseline PSA, prostate volume, family history of PCa, and dutasteride use, in addition to smoking, diabetes, coronary artery disease, age, race, and world region.

Men from North America received PDE5is at higher rates, so a secondary analysis was performed of this subset. Although fewer PCa diagnoses were made in the group, results did not reach statistical significance.

A previous retrospective study by Anthony H. Chavez, MD, and colleagues in the Asian Journal of Andrology, in contrast, found that PDE5i users had less risk of PCa diagnosis (2013;15:246-248). Dr Freedland and his team pointed out that those results were not adjusted for PSA, biopsy rates, and temporal trends. Other studies examining PDE5i use and biochemical recurrence have found conflicting results, including no change, increased risk, and delayed onset.

Among the limitations of the current study, PDE5i use was low, non-randomized, and self-reported with no information on dosage or duration. “Future studies with longer followup and larger study populations are warranted to determine the association between PDE-5i and prostate cancer,” according to Dr Freedland and colleagues.

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1. Jamnagerwalla J, Howard LE, Vidal AC, et al. The Association between Phosphodiesterase Type 5 Inhibitors and Prostate Cancer: Results from the REDUCE Study. J Urol. 2016 Apr 5. pii: S0022-5347(16)30127-6. doi: 10.1016/j.juro.2016.03.172. [Epub ahead of print].

2. No Link Found between Erectile Dysfunction Drugs and Risk of Prostate Cancer. Elsevier. 2016 Aug 1. [press release]