Sexuality and Reproductive Issues (PDQ®): Supportive care - Health Professional Information [NCI] - Treatment of Sexual Problems in People With Cancer
In a study of brachytherapy in the treatment of localized prostate cancer, sildenafil improved potency in 62% to 70% of patients. Patients who were not being treated with androgen therapy had a significantly better response. Similarly, of men who became impotent after brachytherapy for prostate cancer, 85% to 88% responded with improved erectile function when taking sildenafil. Reported potency rates after prostate brachytherapy are high; a 3-year follow-up study demonstrated that 80% of patients were able to have erections adequate for satisfactory sexual activity with or without sildenafil.[Level of evidence: II] Sildenafil has also improved erectile function for patients with partial parasympathetic nerve disruption from rectal surgery.[Level of evidence: I][Level of evidence: II] No other treatment for erectile dysfunction has a high rate of patient acceptance. Sildenafil has been studied in a novel primary prevention modality using nightly administration after a bilateral nerve-sparing prostatectomy. This approach effected a sevenfold improvement in return of spontaneous, normal erectile function 2 months after discontinuation of the drug.[Level of evidence: IV] The authors state that this effect appears to be mediated by properties unique to sildenafil that include improved endothelial function and neuronal regeneration and neuroprotection.
Published data also suggest that early use of sildenafil after radical retropubic prostatectomy may preserve intracorporeal smooth muscle content;[Level of evidence: II] although this effect on the return of potency is not known, maintaining the pro-erectile ultrastructure is integral to rehabilitating erectile function after radical retropubic prostatectomy. Data on the efficacy of early postoperative erectile treatment rely on very few randomized trials. Because the natural recovery of erectile function has been reported to take as long as 2 years, larger randomized trials with at least 2 years of follow-up are needed before definitive conclusions can be drawn about the true efficacy of rehabilitative sexual therapy for postoperative erectile function.
There are three PDE-5 inhibitors approved by the U.S. Food and Drug Administration (FDA) on the market: Viagra (sildenafil), Levitra (vardenafil), and Cialis (tadalafil). Although all three of these oral medications are PDE-5 inhibitors, they are not the same. No head-to-head comparison trials have been published. It appears, however, that all three agents are similar in efficacy, helping 60% to 70% of patients with erectile dysfunction.[Level of evidence: I][24,25] However, comparisons of the efficacy of the PDE-5 inhibitors are complicated by the heterogeneity of the populations studied, the varied primary cancer therapies employed, different timing in measuring outcomes in the clinical trials, and variance in the endpoints used to determine efficacy. Furthermore, most of these trials were industry sponsored.
The major contraindications for use of a PDE-5 inhibitor are concurrent use of nitrates or the alpha-blockers terazosin (Hytrin) and doxazosin (Cardura). The major difference in the three approved inhibitors is that tadalafil has a considerably longer serum half-life, which provides both a larger window of opportunity and potential side effects.[24,25] There is far more research on the use of sildenafil than on the use of the other PDE-5 inhibitors in oncology patients, as it was approved in 1998; vardenafil and tadalafil were approved in 2003. Tadalafil was investigated in the treatment of erectile dysfunction following bilateral nerve-sparing radical retropubic prostatectomy. Results from this randomized, double-blind, placebo-controlled, multicenter study found that 71% of patients randomly assigned to receive tadalafil reported improved erections.[Level of evidence: I] Vardenafil had been investigated in the treatment of erectile dysfunction after radical retropubic prostatectomy and following nerve-sparing radical prostatectomy.[27,28][Level of evidence: I] In post–radical retropubic prostatectomy patients, the average intercourse success rate per patient receiving 20 mg of vardenafil was 74% in men with mild to moderate erectile dysfunction and 28% in men with severe erectile dysfunction, compared with 49% and 4% for placebo. Patients receiving 10-mg and 20-mg doses of vardenafil following nerve-sparing radical prostatectomy reported significantly greater intercourse satisfaction, orgasmic function, and overall satisfaction rate with hardness on the IIEF, compared with those receiving placebo.