Who Benefits From a Prostate Rectal Spacer? Secondary Analysis of a Phase III Trial

作者：Thomas J. Quinn, Stephanie Daignault‐Newton, Walter Bosch, Neil Mariados, John Sylvester, Dhiren Shah, Eric Gross, Richard Hudes, David Beyer, Steven Kurtzman, Jeffrey A. Bogart, R.A. Hsi, Michael Kos, Rodney J. Ellis, Mark D. Logsdon, S.H. Zimberg, Kevin Forsythe, Hong Zhang, Edward Soffen, Patrick Francke, C.A. Mantz, Theodore L. DeWeese, Hiram A. Gay, Jeff M. Michalski, Daniel A. Hamstra · 发表于：Practical Radiation Oncology · 年份：2020 · DOI：10.1016/j.prro.2019.12.011 · 被引用次数：19 · 研究领域：Prostate Cancer Diagnosis and Treatment、Advanced Radiotherapy Techniques、Colorectal Cancer Surgical Treatments

PURPOSE: Previously a phase III trial of a hydrogel rectal spacer during prostate radiation therapy found decreased toxicity and a clinically significant improvement in bowel quality of life (QOL) at 3 years by the Expanded Prostate Cancer Index. We performed a secondary analysis to identify men less likely to benefit. METHODS AND MATERIALS: Clinical and dosimetric data for the 222 patients enrolled on the SpaceOAR phase III trial were analyzed. The volume of rectum treated to 70 Gy (V70) and the quantitative analysis of normal tissue effects in the clinic (QUANTEC) rectal dose goals were used as surrogates for clinical benefit and plan quality. Mean bowel QOL was assessed at 15 and 36 months posttreatment and the likelihood of 1× (5 points) or 2× (10 points) minimally important difference changes were assessed. RESULTS: Rectal V70 was correlated with physician scored toxicity (P = .033) and was used as a surrogate for plan quality. There was no correlation between prostate volume and rectal V70 (r = 0.077). Rectal V70 pre- and post-hydrogel was 13% and 3% for the smallest prostates (<40 mL) and 12% and 2% for the largest (>80 mL). The relative reduction in rectal V70 of 78% did not vary by prespacer V70, but the absolute reduction was greater for a higher V70. All spacer plans met the 5 QUANTEC rectal dose constraints, although 92% of control plans met all constraints. At 3 years, those not meeting all QUANTEC goals had a 15.0-point (standard deviation 15.1) decline, control...