Base International Index of Erectile Function score predicts post-radiation therapy erectile function

August 1, 2009

A study by psychologists and urologists has found that factors affecting erectile function after prostatectomy have much the same impact after other prostate cancer treatments.

Chicago-It has been reasonably well established that vascular risk factors such as diabetes and coronary artery disease have a significant impact on erectile dysfunction before and after radical prostatectomy, but little is known about how those factors might affect patients undergoing radiation therapy for prostate cancer.

A study by psychologists and urologists at Memorial Sloan-Kettering Cancer Center helps correct that omission by showing that the factors affecting erectile function after prostatectomy have much the same impact after brachytherapy, external beam therapy, or a combination of the two. Specifically, the study concludes that each vascular risk factor that is present prior to surgery is likely to decrease International Index of Erectile Function–Erectile Function Domain (IIEF–ED) scores by 1.3 points at 24 months post-treatment.

"We wanted to look at this because it has been established that vascular diseases are associated with erectile dysfunction in non-cancer populations, but from a research perspective, that connection was never made in men after radiation treatment for prostate cancer," Christian J. Nelson, PhD, assistant attending psychologist in the Memorial Sloan-Kettering department of psychiatry and behavioral sciences, told Urology Times.

Vascular risk factors mentioned in Dr. Nelson's presentation at the AUA annual meeting were hypertension, hypercholesterolemia, diabetes mellitus, coronary artery disease, and smoking.

The study population comprised 119 patients with an average age of 67±7 years at the time of their radiation treatment for localized prostate cancer. Of these men, 56 underwent brachytherapy at a median dose of 144 Gy and 58 received external beam treatments at an average dose of 86 Gy. Five men underwent combined therapy.

Sexual function status was assessed with IIEF–ED questionnaires administered at baseline and at various post-treatment intervals. Researchers excluded patients who were receiving androgen deprivation therapy. Vascular morbidities reported by the patients included hypertension, hypercholesterolemia, diabetes mellitus, coronary artery disease, and a history of smoking. The factor most frequently seen was hypertension, present in 37% of the men. Hypercholesterolemia was present in 30%, followed by coronary artery disease in 12%, diabetes mellitus in 9%, and cigarette smoking in 9%.

Dr. Nelson noted that these percentages were representative of men in this age group and that the presence of one or more of these diseases might be considered an indication for radiation therapy, rather than surgical intervention.

Patients then were divided into two groups: those with one risk factor (90 men) and those with two or more risk factors (29 men).

Researchers noted a trend toward a difference between the number of vascular risk factors and erectile function scores at baseline. Those men with one risk factor showed an IIEF–ED score of 23.7 compared to those with two or more risk factors, who had an average score of 20.3 (p=.06). This trend grew to a significant difference between the two groups at 24 months, when men presenting with one risk factor attained an IIEF–ED score of 19.2 and those with two or more risk factors had a score of 14.2 (p<.01). Baseline IIEF–ED scores appeared to be the strongest predictor of erectile function outcomes, followed by the number of risk factors and the patient's age.

Dr. Nelson acknowledged the study's weaknesses. The risk factors were self-reported and, given the character of the treatment, more accurate follow-up data might be obtained at 36 months. In addition, a larger study might elucidate the impact of risk factors, perhaps specific risk factors, more clearly. Nevertheless, Dr. Nelson said, the study provided information that would be valuable in counseling patients who are contemplating radiation therapy.