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Evaluation of sexual function on a randomized trial of a prostate rectal spacer.
Background: The SpaceOAR phase 3 trial showed that a hydrogel spacer between the prostate and rectum decreased rectal dose and toxicity while improving bowel quality of life (QOL) after image guided prostate IMRT to 79.2 Gy. Here we evaluated dose to penile bulb as well as sexual function on this trial Methods: Sexual QOL was measured with the Expanded Prostate Cancer Index Composite (EPIC) by mean summary scores and the proportion of patients with a minimally important decline (MID) (11 points). Stratification was based on severe erectile dysfunction (ED)(EPIC < = 60) vs not. The single question on “Erections sufficient for intercourse over the preceding 4 weeks” was also evaluated. Results: Median Follow-up was 37 months with 63% of men evaluable at 3 years. With spacer the dose to the penile bulb was reduced for mean (21 vs 11 Gy), Dmax (46 vs 36 Gy), and V10-V30 (all p < 0.05). Baseline sexual function was 53 (±24) with 54% having severe ED with no difference between arms (p > 0.1). At 3 years average EPIC score was 39.7 (± 23) and 82% had severe ED with no differences between arms (p > 0.1). At enrollment 42% had EPIC > 60 with average summary of 77 (±8.3) which at 3 years was 53 (±24.8). In this sub-group at 3 years a higher EPIC was observed on the Spacer arm (57.7 (±24.1) vs. 44.6 (± 24.4)) which met the threshold for an MID without statistical significance (p = 0.07). Based on MID and twice that there was a trend favoring Spacer with 53% vs 75% for 11-point decline (p = 0.064) and 41% vs 60% for 22 point decline (p = 0.11). A small number of these men were potent at baseline and evaluable both at baseline and 3 years (n = 49). Of these 37.5% in the Control arm had erections sufficient for intercourse at 3 years as compared to 66.7% (p = 0.07) in the Spacer arm. Power analysis revealed 35% power to detect a change of 11 points between arms and 27% power to detect a difference of 22 points. Conclusions: The use of a hydrogel spacer decreased dose to the penile bulb with a suggestion of a clinically significant improvement in patient reported sexual function and potency. These did not achieve statistical significance potentially due to the high prevalence of ED at baseline and, therefore, the small evaluable sample size. Analysis of penile bulb dose and QOL is ongoing. Clinical trial information: NCT01538628
Abstracts by Daniel A. Hamstra:
- Meeting: 2015 Genitourinary Cancers Symposium | Abstract No: 04
Concurrent gemcitabine (GEM) and radiotherapy (XRT) as organ-sparing treatment for muscle-infiltrating bladder cancer (MIBC): Preliminary results of a patient-based cumulative analysis of seven phase I-II trials.Meeting: 2015 Genitourinary Cancers Symposium | Abstract No: 306