ED drugs and risk for prostate cancer recurrence? … NOT!


Back in February 2015 a group of German researchers published a study suggesting that there was a small but significantly increased risk of biochemical recurrence after prostate cancer treatment among men using drugs like sildenafil (Viagra) to recover/stimulate erectile function.

The German research team themselves found this result to be astonishing. So did we, and we didn’t report on it because we thought it was really very odd. The effect was small, and we were pretty sure that there would be “more to come.” Even the German research team said at the time that

Our results need to be interpreted with caution

and

We still advise our patients to use PDE5 inhibitors on demand.

The original study was published by Michl et al. in the Journal of Urology. It was based on an  analysis of data from 4,752 consecutive patients with localized prostate cancer, all treated with nerve-sparing radical prostatectomy at a single, high volume clinic between January 2000 and December 2010. Here’s a quick summary of those data:

  • 1,110/4,752 patients (23.4 percent) received PDE5 inhibitors post-surgery.
  • 3,642/4,752 patients (76.6 percent) did not.
  • Median follow-up was 60.3 months.
  • Five-year biochemical recurrence-free survival estimates were
    • 84.7 percent among the men treated with the PDE5 inhibitors
    • 89.2 percent among the men not treated with PDE5 inhibitors
    • This difference was small but highly statistically significant (p = 0.0006).

The authors concluded that

Contrary to experimental data, the use of phosphodiesterase type 5 inhibitors after radical prostatectomy may adversely impact biochemical recurrence. Further studies are needed to validate our results.

Additional information about this study (as of January 27, 2015) can be found on the Medscape Oncology web site.

Now, as can be seen from a new article just published by Loeb et al. in European Urology, and discussed in another commentary on the Medscape Oncology web site (as of February 2, 2016), data from a somewhat larger study has shown no association between PDE5 inhibitor use after radical prostatectomy and risk for biochemical recurrence.

Loeb and her colleagues used data from the National Prostate Cancer Register of Sweden (which is linked to data in the Swedish Prescribed Drug Register.) They used these databases to identify men with localized prostate cancer who underwent primary radical prostatectomy or radiation therapy during 2006 and 2007 and who had a 5-year history of post-treatment follow-up. Here are their key data:

  • 293 men (cases) had biochemical recurrence post-treatment.
  • For each case of the 293 cases they identified 20 biochemical recurrence-free controls (n = 5,767).
  • PDE5 inhibitorss were used after treatment by
    • 150/293 men (51 percent) in the recurrence group
    • 3,334/5,767 men (58 percent) in the control group
  • PDE5 inhibitor use was not associated with biochemical recurrence after
    • Radical prostatectomy (odds ratio [OR] = 0.78)
    • Radiation therapy (OR = 0.98)
  • These results included appropriate adjustments for marital status, education, income, PSA level, clinical stage, Gleason score, and proportion of positive biopsies.
  • Results were similar after additional adjustment for surgical pathology (OR = 0.86).
  • Men whose cumulative use of PDE5 inhibitor pills was above the median had
    • A slightly lower risk of biochemical recurrence after prostatectomy in the clinical model
    • No difference in risk for biochemical recurrence after adjustment for pathologic tumor features

Loeb et al. conclude that:

Our results from a population-based cohort suggest that … risk [for biochemical recurrence] is not higher among men using [PDE5 inhibitors] after prostate cancer treatment.

Quite why the original German researchers got a different result is still a little unclear, but current thinking seems to be there is no good reason to think that using a PDE5 inhibitor to help with recovery of erectile function after treatment for prostate cancer is actually associated with any meaningful increase in risk for biochemical recurrence.

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