Nerve-sparing radical prostatectomy (NSRP) is the gold-standard therapy for
prostate cancer in men with a life expectancy of 10 years or more. The risk
of erectile dysfunction (ED) following NSRP is significant. This is caused
by neuropraxia - the usually temporary failure of nerve conduction in the
absence of structural changes due to compression, ischemia or blunt injury -
which inevitably occurs during the procedure. Ultimately this may lead to
the development of fibrosis within the corpus cavernosa and cause ED.
To prevent the onset of postoperative ED, the use of phosphodiesterase type
5 (PDE5) inhibitors was introduced. These agents prevent the breakdown of
cyclic guanosine monophosphate in cavernosal tissue, which plays a role in
the prevention of cell death and fibrosis, and may thus exert a protective
effect on cavernosal smooth muscle.
Participants were recruited to this first robustly designed, evidence-based,
multi-centre study approximately one month before they were scheduled to
undergo NSRP. A total of 423 patients completed the study. The inclusion of
the on-demand dosing regimen enabled comparison of the currently recommended
guidelines for the use of PDE5 inhibitors with a proposed nightly dosing
regimen, which was suggested to have potential positive effects on erectile
function. The results clearly show that nightly dosing with vardenafil does
not have any effect beyond that of on-demand use.
The study shows that on-demand use of vardenafil during the treatment period
was associated with significantly greater erectile function and sexual
intercourse completion rates compared to placebo. The success rates for the
vardenafil on-demand group were also higher than for the nightly group.
These data indicate that the use of on-demand vardenafil is of greater
benefit than nightly treatment in patients following NSRP surgery and, in
general, support the on-demand use of PDE5 inhibitors following NSRP surgery
over a daily dosing regimen. This prompts reconsideration of the current
practice of prescribing nightly PDE5 inhibitor therapy, as on-demand use of
vardenafil is equally effective in men with ED following NSRP, a notoriously
difficult-to-treat patient population.
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