Radiation-associated impotence. A clinical study of its mechanism.

External beam pelvic irradiation in men is frequently complicated by erectile dysfunction. We tested the erectile function in 23 patients (mean age, 65 years) who received radiation therapy for prostate cancer. Fifteen patients experienced changes in erectile potency following radiotherapy. Neurological, endocrine, and vascular testing revealed abnormalities in 0, 5, and 15 of these patients, respectively. In two, arteriography revealed bilateral occlusive disease in the distal internal pudendal and penile arteries overlying the pelvic radiation field. A significant difference with cigarette smoking was found among the 15 patients whose erectile capacity decreased and the four patients whose capacity remained unchanged. Vasculogenic impotence is the most consistent organic erectile abnormality in RAI.