Objectives: To assess the efficacy and factors associated with successful treatment of sildenafil citrate for erectile dysfunction after radical prostatectomy (RP).
Methods: Of the 470 patients who underwent RP at our institution between July 1998 and January 2000, 227 (48%) sought treatment for erectile dysfunction, and 174 (37%) were prescribed sildenafil citrate. The starting dose was 50 mg, which was increased to 100 mg if the patient did not have a positive response. Of the 174 patients, 104 (59.8%) had undergone a bilateral nerve-sparing (NS) procedure, 28 (16.1%) had undergone a unilateral NS procedure, and 42 (24.1%) had undergone a non-NS procedure. Erectile function was assessed by the abridged five-item version of the International Index of Erectile Function questionnaire, referred to as the Sexual Health Inventory for Men (SHIM), at baseline and 1 year after sildenafil use. The patients' charts were retrospectively reviewed to find factors associated with a successful outcome, which was defined as successful vaginal intercourse. Association with success was assessed by chi-square analysis and the Cochran Armitage test for trend. Bonferroni correction for multiple comparisons was used, with an overall significance level of 0.05 for each factor assessed.
Results: The mean age was 60.1 +/- 6.25 years, and the mean interval from RP to drug use was 3 months. After treatment with sildenafil, 100 (57%) of 174 patients responded to the drug: 79 (76%) of 104 in the bilateral NS group, 15 (53.5%) of 28 in the unilateral NS group, and 6 (14.2%) of 42 in the non-NS group. SHIM analysis showed that the magnitude of the improvement was greater in the bilateral NS group (19.97 +/- 1.12) than in the unilateral NS (15.89 +/- 3.38) or non-NS (10.06 +/- 2.0) groups (P <0.020). Four factors were significantly associated statistically with a successful outcome: the presence of at least one neurovascular bundle, a preoperative SHIM score of 15 or greater, age 65 years old or younger, and interval from RP to drug use of more than 6 months (P <0.001).
Conclusions: The efficacy of sildenafil citrate after RP correlated with the degree of neurovascular bundle preservation, preoperative erectile function status, age, and interval before starting treatment.