Efficacy of Sildenafil Citrate (Viagra) after Radical Prostatectomy

Efficacy of Sildenafil Citrate (Viagra) after Radical Prostatectomy
Craig D. Zippe, M.D. and Ashok Agarwal, Ph.D.

The recent release of sildenafil citrate (Viagra), an inhibitor of phosphodi-esterase 5, has dramatically changed the treatment options for patients with erectile dysfunction. Despite the current enthusiasm for this drug, there are no reports on its effectiveness in the subgroup of patients with erectile dysfunction following radical prostatectomy. Previous publications have failed to clearly identify organic causes of erectile dysfunction to assess the efficacy of sildenafil in post-prostatectomy patients.

Study Seeks to Determine Efficacy
We sought to determine if post-prostatectomy patients with erectile dysfunction would respond to sildenafil and if the type of surgery they had (nerve-sparing or nonnerve-sparing) affected response rates. Among those who responded, we sought to determine how many doses of sildenafil were needed for a response, the duration of intercourse and whether the spouse reported being satisfied.

Baseline and follow-up data from 28 patients presenting with erectile dysfunction following radical prostatectomy were obtained (Table 1). Patients receiving any neoadjuvant/adjuvant hormones or adjuvant radiation therapy were excluded. During interviews, patients reported what their erectile status was before surgery, before sildenafil therapy and after using a minimum of four doses of sildenafil. Both the patients and their spouses were interviewed using a uniform post-prostatectomy questionnaire that included questions about response to therapy, duration of intercourse, spousal satisfaction, side effects and related topics. The patients were compared based on the type of surgical procedure they had undergone (nerve-sparing or nonnerve-sparing). A positive response to sildenafil was defined as erection sufficient for vaginal-penetration.

Study Shows Positive Results
Twelve of the 15 patients (80%) who had bilateral nerve-sparing procedures had a positive response to sildenafil, with a mean duration of 6.92 minutes of vaginal intercourse (Table 2). These 15 patients also reported a spousal satisfaction rate of 80%. All 12 of the responders had a positive response within the first three doses, and 10 of the 12 responded with the first or second dose. None of the three patients who had had unilateral nerve-sparing procedures responded, nor did any of the 10 patients who had had a nonnerve-sparing procedure. The two most common side effects of the drug seen in all of the 28 patients were transient headaches (39.3%) and abnormal color vision (10.7%). No patients discontinued the medication because of its side effects.

The most salient finding of this study is how well patients who had bilateral nerve-sparing procedures responded to sildenafil. After one to three doses, the majority of these patients (80%) achieved erections sufficient for vaginal intercourse. This response was directly related to spousal satisfaction, again confirming the quality of the erection. The lack of a response to sildenafil in the three patients who had had unilateral nerve-sparing procedures (as in the nonnerve-sparing group) is unclear due to small sample size. More patients will have to be studied in this subgroup to accurately determine the efficacy of sildenafil.

Patients May Benefit from Sildenafil Earlier
The mean time interval from radical prostatectomy to the initiation of sildenafil was roughly one year in both the nerve-sparing and non-nerve-sparing groups. It is quite possible that earlier initiation of sildenafil might increase the positive response rate in both groups. Prospective studies are under way to assess the efficacy of sildenafil in the immediate postoperative period after radical prostatectomy.

This study has important implications in the surgical management of prostate cancer at a time when the morbidity of radical prostatectomy is being severely scrutinized. Sildenafil offers a chance to treat roughly 80% of our impotent patients if a bilateral nerve-sparing procedure is done.

Although potency rates of 50 to 70% after nerve-sparing radical prostatectomy have been reported, these figures are not universally accepted. Jonler and associates, from the University of Wisconsin, report that only 9% of their patients had full erections and partial erections in 38% after nerve-sparing prostatectomy. Similar figures were reported by Fowler in 1993 in a Medicare population. Tallot et al from the Dana Farber Cancer Institute, described inadequate erections and vaginal penetration in 79% of men who had bilateral nerve-sparing procedures, and found no benefit to the unilateral nerve-sparing procedure.

Nerve-sparing Procedure Shows Benefit
Our findings will allow us to reexamine the indication for nerve-sparing radical prostatectomy. In general, an inexperienced surgeon will have greater blood loss and more iatrogenic positive margins, and will require more operative time, when performing nerve-sparing procedures than when performing simpler nonnerve-sparing procedures. We hope our study will encourage surgeons to become more skilled at nerve-sparing procedures and perform more of them, especially for low-volume tumors, to give their patients the best chance of successful treatment for post-prostatectomy impotence.