Sildenafil citrate (Viagra) and erectile dysfunction following external beam radiotherapy for prostate cancer: a randomized, double-blind, placebo-controlled, cross-over study.

Purpose: To determine the efficacy of sildenafil citrate (Viagra) in patients with erectile dysfunction after three-dimensional conformal external beam radiotherapy (3D-CRT) for prostate cancer.
Methods and Materials: 406 patients with complaints of erectile dysfunction and who completed radiation at least 6 months before the study were approached by mail. 3D-CRT had been delivered (mean dose 68 Gy). Sixty patients were included and entered a double-blind, placebo-controlled, cross-over study lasting 12 weeks. They received during 2 weeks 50 mg of sildenafil or placebo; at Week 2 the dose was increased to 100 mg in case of unsatisfactory erectile response. At Week 6, patients crossed over to the alternative treatment. Data were collected using the International Index of Erectile Function (IIEF) questionnaire, and side effects were recorded.
Results: Mean age was 68 years. All patients completed the study. For most questions of the IIEF questionnaire there was a significant increase in mean scores from baseline with sildenafil, but not with placebo. Ninety percent of the patients needed a dose adjustment to 100 mg sildenafil. Side effects were mild or moderate.
Conclusion: Sildenafil is well tolerated and effective in improving erectile function of patients with ED after 3D-CRT for prostate cancer.