Continued Benefit to Rectal Separation for Prostate RT: Final Results of a Phase III Trial

Publication date: Available online 23 December 2016
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Daniel A. Hamstra, Neil Mariados, John Sylvester, Dhiren Shah, Lawrence Karsh, Richard Hudes, David Beyer, Steven Kurtzman, Jeffrey Bogart, R. Alex Hsi, Michael Kos, Rodney Ellis, Mark Logsdon, Shawn Zimberg, Kevin Forsythe, Hong Zhang, Edward Soffen, Patrick Francke, Constantine Mantz, Peter Rossi, Theodore DeWeese, Stephanie Daignault-Newton, Benjamin W. Fischer-Valuck, Anupama Chundury, Hiram Gay, Walter Bosch, Jeff Michalski
BackgroundSpaceOAR®, an FDA approved hydrogel intended to create rectal-prostate space, was evaluated in a single blind Phase III trial of image-guided intensity-modulated RT (IG-IMRT, XXXX XXXX, IJROBP 2015). Men (n=222) were randomized 2:1 (Spacer:Control) receiving 79.2/1.8 Gy to prostate ± seminal vesicles. We now report final results with 3-year median follow-up.Materials and MethodsCumulative (CTCAE v 4.0) toxicity was evaluated by log-rank test. For quality-of-life (QOL) the Expanded Prostate Cancer Index Composite (EPIC) was utilized and mean changes from baseline in EPIC domains were tested by repeated measures models. Proportions of men with minimally important differences (MID) in each domain were tested using repeated measures logistic models with pre-specified thresholds.ResultsThe 3-year incidence of rectal toxicity of grade >=1 (9.2% vs 2.0%, p=0.028) and >=2 (5.7% vs 0%, p=0.012) favored Spacer. Grade 1+ urinary incontinence was also lower in the Spacer arm (15% vs. 4%, p=0.046) with no difference in grade 2+ urinary toxicity (7% vs 7% p=0.7). From 6-months onward bowel QOL consistently favored Spacer (p=0.002) with the difference at 3-years (5.8-points, p<0.05) meeting threshold for a MID. Interestingly, Control men at 3-years had a 3.9-point greater decline in urinary QOL vs Spacer (p<0.05) but did not meet the MID threshold. At 3- years more men had a MID decline in bowel QOL for Control vs. Spacer (41% vs. 14%, p=0.002) as well as for urinary QOL (30% vs 17%, p=0.04).Further, Control men were also more likely to see large declines (twice MID) in bowel (21% vs 5%, p=0.02) and urinary QOL (23% vs. 8%, p=0.02).ConclusionThe benefit of a hydrogel spacer in reducing rectal dose, toxicity, and QOL declines following IG-IMRT for prostate cancer were aintained or increased with longer follow-up providing stronger evidence for the benefit of hydrogel spacer for prostate radiotherapy.

Teaser

A phase 3 trial was performed using an absorbable hydrogel (SpaceOAR System®) to provide space between the prostate and rectum for men receiving dose-escalated prostate radiotherapy. At 3-years men on the Spacer arm had decreased bowel toxicity and less decline in both urinary and bowel quality of life as compared to Control men.


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