Sexual quality of life following prostate intensity modulated radiation therapy (IMRT) with a rectal/prostate spacer: Secondary analysis of a phase 3 trial

Background: We previously reported the results of a phase 3 trial evaluating a prostate/rectal hydrogel spacer during prostate intensity modulated radiation therapy, which resulted in decreased rectal dose and toxicity and less decline in bowel quality of life (QOL). A secondary analysis was performed to correlate penile bulb dose and sexual QOL. Methods and materials: Sexual QOL was measured with the Expanded Prostate Cancer Index Composite (EPIC) by mean scores, the proportion of patients with a minimal clinically important difference (MID), and analyses of the different items composing the sexual domain. Results: A total of 222 men enrolled with median follow-up of 37 months. Hydrogel reduced penile bulb mean dose, maximum dose, and percentage of penile bulb receiving 10 to 30 Gy (all P < .05) with mean dose indirectly correlated with erections sufficient for intercourse at 15 months (P = .03). Baseline EPIC was low (53 [standard deviation +/- 24]) with no difference between arms (P < .1). A total of 41% (88/222) of men had adequate baseline sexual QOL (EPIC >60 (mean, 77 [+/- 8.3]). This subgroup at 3 years had better sexual function (P = .03) with a spacer with a smaller difference in sexual bother (P = .1), which resulted in a higher EPIC summary on the spacer arm (58 [+/- 24.1] vs control 45 [+/- 24.4]) meeting threshold for MID without statistical significance (P = .07). There were statistically nonsignificant differences favoring spacer for the proportion of men with MID and 2x MID declines in sexual QOL with 53% vs 75% having an 11-point decline (P = .064) and 41% vs 60% with a 22-point decline (P = .11). At 3 years, more men potent at baseline and treated with spacer had erections sufficient for intercourse (control 37.5% vs spacer 66.7%, P = .046) as well as statistically higher scores on 7 of 13 items in the sexual domain (all P < .05). Conclusions: The use of a hydrogel spacer decreased dose to the penile bulb, which was associated with improved erectile function compared with the control group based on patient-reported sexual QOL. (C) 2017 The Authors. Published by Elsevier Inc.on behalf of American Society for Radiation Oncology.