Men who use oral erectile dysfunction drugs following radical prostatectomy (RP) for prostate cancer (PCa) may be at elevated risk of biochemical recurrence of their malignancy, according to a new study.

The retrospective study included 4,752 consecutive patients with localized PCa treated with bilateral nerve-sparing RP, of whom 1,110 (23.4%) received selective phosphodiesterase type 5 (PDE5) inhibitors after RP and 3,642 (76.6%) did not. PDE5 inhibitors included sildenafil, vardenafil, and tadalafil. The study population had a median follow-up of 60.3 months.

Overall, the 5-year biochemical recurrence (BCR)-free survival estimates were significantly lower in the group who used PDE5 inhibitors compared with non-users (84.7% vs. 89.2%), Uwe Michl, MD, of the Martini-Clinic Prostate Cancer Center in Hamburg, Germany, and colleagues reported in The Journal of Urology (2015;193;479-483). In multivariate analysis, use of PDE5 inhibitors was independently associated with a significant 38% increased risk of biochemical recurrence.

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Dr. Michl’s team propensity score matched 1,102 PDE5 inhibitor users to 1,102 non-users and found that 5-year BCR-free survival rates remained significantly lower in men who used the medications (84.6% vs. 89.1%).

The investigators said they believe that, to their knowledge, the study is the first to identify an adverse effect of selective PDE5 inhibitors on biochemical outcome following RP. They noted that the finding was unexpected given the previously reported antineoplastic effects of PDE5 blockade in different animal models. 

In addition, they pointed out that their data contrast with study findings reported by Anthony H. Chavez, MD, of Scott & White Healthcare in Temple, Tex., and colleagues in the Asian Journal of Andrology (2013;15:246-248), which showed that the use of PDE5 inhibitors in ED patients without a history of PCa was associated with a decreased incidence rate of PCa.

The authors, who noted that PDE5 inhibitors are widely used to treat ED following RP, stated that they can only speculate about possible causes of an adverse effect of selective PDE5 inhibitors on post-RP biochemical outcomes. Conceivable causes include the effects of the drugs on the immune system, autonomic nerve development, and angiogenesis.