Introduction

We conducted a longitudinal prospective study to evaluate the effect of radiation doses on the development of brachytherapy-induced erectile dysfunction by using the International Index of Erectile Function-15 (IIEF-15)._x000D_ _x000D_

Methods

From September 2004 to May 2010, we identified 48 patients whose erectile function (EF) score was 11 or greater and who did not receive any supplemental therapy. Iodine-125 seed was used and was conducted by peripheral loading. Dosimetric parameters were collected as follows; mean dose to 90% of prostate volume (total D90), percentage of prostate volume receiving at least 100% dose (total V100), and 150% dose (total V150). We also defined prostate apex as a 10 mm range from the distal edge of the prostate, and constructed a 3D model of the prostate and rectum for evaluating the radiation dose and exposed area (Figure). We prospectively collected IIEF-15 questionnaires after PB for at least 2 years after treatment. We defined an EF domain score change to less than 10 as worsened EF severity.

Results

Mean patient age was 65.5±7.0 years with a median follow-up time of 34 months. Mean clinical target volume was 26.7±6.53 cc, and the mean outcomes of the dosimetric parameters were: total D90; 175.6±21.8 Gy, total V100; 95.3±3.53%, total V150; 70.6±11.4%, apex V100; 95.3±6.10%, and apex V150; 68.7±18.3%, respectively. Total IIEF-15 score was 49.9±12.0 before PB, but decreased to 34.7±20.3 12 months after PB (p<0.05). Among the 48 patients, 32 (75.0%) had a deterioration of their EF score 12 months after PB. Mean age in the worsened EF severity group was 63.9 years, which was significantly lower than that in their counterparts (67.8 years, p=0.029). Furthermore, 47.9% and 58.3% of patients in the worsened EF severity group had significantly more total V100 ≥95% and apex V150 ≥70%, respectively, as compared to those in their counterparts (12.5%, p=0.024 and 18.3%, p=0.003, respectively). On multivariate analysis, an age ≥70 and apex V150 ≥70% were independent predictors of deteriorated EF severity 12 months after PB (p=0.024, HR=7.91, p=0.007, HR=7.75, respectively).

Conclusions

An excessive dose of radiation to the apex area of the prostate as well as advanced age may have an influence on worsening potency preservation after PB.

Funding

none_x000D_