Objectives: To determine the response to sildenafil citrate (Viagra) in patients with erectile dysfunction after radiation therapy for localized prostate cancer.
Methods: Baseline and follow-up data from 21 patients presenting with erectile dysfunction after radiation treatment for clinical T1-2 prostate cancer were obtained. Two patients had undergone iodine-125 seed implantation and the remaining 19 conformal external beam irradiation. All 21 patients were considered to have erectile dysfunction as assessed by the International Index of Erectile Function (IIEF) and were prescribed sildenafil at a dosage of 50 mg, with a titration to 100 mg if needed. The mean time between the completion of radiation therapy and initiation of sildenafil was 24.6 +/- 5.8 months. The quality of the erectile function was assessed after a minimum of four doses by using the Cleveland Clinic Erectile Function (CCEF) questionnaire and the IIEF questionnaire. A positive response to sildenafil on the CCEF questionnaire was defined as an erection sufficient for vaginal penetration. The responses on the IIEF questionnaire were rated on a scale of 1 (almost never) to 5 (almost always), with 0 being no sexual activity.
Results: On the CCEF questionnaire, 71% (15 of 21) of patients had a positive response, with a mean duration of 12.7 +/- 2.5 minutes of intercourse, and a corresponding spousal satisfaction rate of 71%. Twelve (80%) of the 15 responders required titration to the 100-mg dosage for maximal effect. The most common side effects seen were transient flushing (19%), abnormal color vision (14%), and headaches (10%). No patient discontinued the drug because of side effects. On the IIEF questionnaire, the responses to questions 3 (frequency of penetration), 4 (maintenance of erection), 7 (satisfactory intercourse), and 15 (erection confidence) increased from mean baseline scores of 1.3, 1.1, 1.2, and 1.8 to final mean scores of 4.0, 3.9, 3.2, and 3.4, respectively (P <0.001). On the global efficacy question (ability to achieve firm erections), 71% of the patients responded positively.
Conclusions: Sildenafil citrate can improve the ability to achieve and maintain an erection in most patients with erectile dysfunction after radiation therapy for prostate cancer.