AbstractID: 8095 Title: Correlation Between Radiation Dose to the Proximal Penis and the Development of
Brachytherapy-induced Erectile Dysfunction
Radiation dose to the bulb of the penis and/or the proximal corporeal bodies as predictors for the development of brachytherapy-induced erectile
dysfunction (ED) was evaluated.
30 patients who underwent permanent prostate brachytherapy and developed brachytherapy-induced ED were paired with 30 similar men who
maintained potency after implantation. None of the 60 patients received supplemental external beam radiation therapy and none received
hormones after implant. Potency was assessed by self-administration of a validated erectile function questionnaire. Median follow-up was 48.0
months. The bulb of the penis and the proximal crura were outlined on the day 0 postimplant CT scan. The radiation dose distribution to the
bulb of the penis and adjacent crura was defined in terms of the minimum dose delivered to 25%, 50%, 70%, 75%, 90%, and 95% of the bulb or
the crura (D25, D50, D70, D75, D90, and D95).
All evaluated dosimetric parameters of the bulb of the penis and the proximal crura were greater in men with brachytherapy-induced ED.
Multivariate analysis indicated that dose to the bulb of the penis and patient age were most predictive of postimplant ED. 90% of the potent
patients had a penile bulb D50 ≤ 40% of mPD whereas 70% of impotent patients had a D50 > 40% of mPD. Dose to the proximal crura was of less
predictive value than dose to the bulb, but a similar cut point for the crura dose was 22% of mPD which was exceeded by 40% of potent men and
60% of impotent men.