Purpose: Impotence is a familiar sequela of both definitive external-beam radiotherapy (EBRT) and radical prostatectomy for localized prostate cancer. Among surgical options, nerve-sparing radical prostatectomy (NSRP) offers the highest potency preservation rate of 70%. We report the change in potency over time in an EBRT-treated population, determine the significantly predisposing health and treatment factors affecting post-EBRT potency, and compare age- and stage-matched potency rates with those of NSRP-treated patients.
Patients and methods: Our results are from a retrospective study of 287 patients diagnosed with prostate cancer in clinical stages A to C and treated with conformal techniques to 6200 to 7380 cGy. Information regarding preradiotherapy potency, medical and surgical history, neoadjuvant antiandrogen use, and post-EBRT potency was documented for each patient. The median follow-up time was 34 months.
Results: At months 1, 20, 40, and 60, actuarial potency rates were 96%, 75%, 59%, and 53%, respectively. Factors identified as significant predictors of post-EBRT impotence include pre-EBRT partial potency, diabetes, coronary artery disease, and anti-androgen medication usage. Among treatment factors, a trend toward potency preservation was noted for the six-field versus the four-field technique. Finally, age- and stage-matched comparisons of potency rates for our population and NSRP-treated patients were performed. For patients older than 70 years, 60.9% of EBRT patients and 32.9% of NSRP patients remained potent after treatment. Overall, EBRT patient potency preservation was 71.3%, versus 66.2% for NSRP patients.
Discussion: Pre-EBRT partial potency, diabetes, coronary artery disease, and anti-androgen medication usage are significant predispositions to impotence in EBRT-treated prostate cancer patients. In comparing EBRT with NSRP for various age and stage groups, EBRT offers notably higher potency preservation rates than NSRP for patients older than 70 years.