Penile erectile function after permanent radioactive seed implantation for treatment of prostate cancer.

PURPOSE: We assess erectile function after prostate brachytherapy and analyze those factors affecting potency preservation.
MATERIALS AND METHODS: A total of 416 patients treated from October 1990 to September 1998 with permanent radioactive seed implantation for T1 to T2 prostate cancer had erectile function assessed before and after treatment. Erectile function was assessed using the scoring system of 0-complete inability to have erections, 1-able to have erections but insufficient for intercourse, 2-can have erections sufficient for intercourse but considered suboptimal and 3-has normal erectile function. Implant dose was defined as the D90, which was the dose delivered to 90% of the gland on a dose volume histogram from the 1-month computerized tomography based dosimetric analysis.
RESULTS: Pretreatment erectile function assessment revealed scores of 0 in 57 (14%), 1 in 46 (11%), 2 in 77 (18%) and 3 in 236 (57%) patients. In 313 patients who were potent with a score 2 or greater before therapy the actuarial freedom from any decrease in erectile function score was 64% and 30% at 3 and 6 years, respectively. The actuarial preservation of potency, with a score 2 or greater, was 79% and 59% at 3 and 6 years, respectively. The 2 factors found to have a significant negative effect on potency in univariate and multivariate analyses were high implant dose (D90 greater than 160 Gy. for I-125 and D90 greater than 100 Gy. for Pd-103) and a pretreatment erectile function score of 2 versus 3.
CONCLUSIONS: The rate of potency preservation after brachytherapy is high, although a decrease occurs from 3 to 6 years. Pretreatment erectile dysfunction as well as higher implant dose are associated with greater impotency.