Hydrogel Spacer Prospective Pivotal Trial

Neil Mariados - Journal Club Review: Hydrogel Spacer Prospective Multicenter Randomized Controlled Pivotal Trial: Dosimetric and Clinical Effects of Perirectal Spacer Application in Men Undergoing Prostate Image Guided Intensity Modulated Radiation Therapy

STUDY SUMMARY: Prostate radiation therapy rectal toxicity is largely due to the prostate-rectum proximity.  A randomized, controlled, multicenter study of an absorbable polyethylene glycol hydrogel perirectal spacer (SpaceOAR System) used in men undergoing image guided prostate intensity modulated radiation therapy was performed.  Spacer safety and effectiveness in consistent perirectal space creation and reduction of rectal irradiation was demonstrated. Spacer use  was associated with low toxicity rates and a reduction in patients experiencing declines in bowel and urinary quality of life.

STUDY ABSTRACT -

PURPOSE: Perirectal spacing, whereby biomaterials are placed between the prostate and rectum, shows promise in reducing rectal dose during prostate cancer radiation therapy.  A prospective multicenter randomized controlled pivotal trial was performed to assess outcomes following absorbable spacer (SpaceOAR system) implantation.

 METHODS AND MATERIALS: Overall, 222 patients with clinical stage T1 or T2 prostate cancer underwent computed tomography (CT) and magnetic resonance imaging (MRI) scans for treatment planning, followed with fiducial marker placement, and were randomized to receive spacer injection or no injection (control). Patients received postprocedure CT and MRI planning scans and underwent image guided intensity modulated radiation therapy (79.2 Gy in 1.8-Gy fractions). Spacer safety and impact on rectal irradiation, toxicity, and quality of life were assessed throughout 15 months.

RESULTS: Spacer application was rated as “easy” or “very easy” 98.7% of the time, with a 99% hydrogel placement success rate. Perirectal spaces were 12.6 3.9 mm and 1.6 2.0 mm in the spacer and control groups, respectively.  There were no device-related adverse events, rectal perforations, serious bleeding, or infections within either group. Pre-to postspacer plans had a significant reduction in mean rectal V70 (12.4% to 3.3%, P<.0001). Overall acute rectal adverse event rates were similar between groups, with fewer spacer patients experiencing rectal pain (PZ.02). A significant reduction in late (3-15 months) rectal toxicity severity in the spacer group was observed (PZ.04), with a 2.0% and 7.0% late rectal toxicity incidence in the spacer and control groups, respectively. There was no late rectal toxicity greater than grade 1 in the spacer group. At 15 months 11.6% and 21.4% of spacer and control patients, respectively, experienced 10-point declines in bowel quality of life. MRI scans at 12 months verified spacer absorption.

CONCLUSION: Spacer application was well tolerated. Increased perirectal space reduced rectal irradiation, reduced rectal toxicity severity, and decreased rates of patients experiencing declines in bowel quality of life. The spacer appears to be an effective tool, potentially enabling advanced prostate RT protocols.

Int J Radiation Oncol Biol Phys, Vol.92, No. 5, pp. 971-977, 2015 0360-3016/ © 2015 The Authors. Published by Elsevier Inc. This is an open access article. DOI: http://dx.doi.org/10.1016/j.ijrobp.2015.04.030 

AUTHORS: Neil Mariados, MD, John Sylvester, MD, Dhiren Shah, MD, Lawrence Karsh, MD, Richard Hudes, MD, David Beyer, MD, Steven Kurtzman, MD,  Jeffrey Bogart, MD, R. Alex Hsi, MD, Michael Kos, MD, Rodney Ellis, MD, Mark Logsdon, MD, Shawn Zimberg, MD, Kevin Forsythe, MD, Hong Zhang, MD, PhD, Edward Soffen, MD, Patrick Francke, MD, Constantine Mantz, MD, Peter Rossi, MD, Theodore DeWeese, MD, Daniel A. Hamstra, MD, PhD, Walter Bosch, DSc, Hiram Gay, MD, and Jeff Michalski, MD, MBA.

About Neil Mariados, MD:  Medical Director of Radiation Oncology - is a Board Certified Radiation Oncologist.  Dr Mariados pursued his undergraduate studies at the University of Ottawa, in Canada where he grew up, and completed an Internal Medicine residency at University of Medicine and Dentistry of New Jersey( UMDNJ).  Dr. Mariados pursued a second residency in Radiation Oncology, at Upstate Medical Center in Syracuse, N.Y. After this residency, he  went on to obtain further specialization and completed a two year fellowship in both Stereotactic Radiosurgery and Brachytherapy at the University of Ottawa, Ottawa, Canada.