title: 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.
abstract: OBJECTIVE
  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
  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 (P=.02). A significant reduction in late (3-15 months) rectal toxicity severity in the spacer group was observed (P=.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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Associated Medical Professionals of New York, Syracuse, New York. Electronic address: nmariados@ampofny.com.
authors.forename: Neil
authors.initials: N
authors.lastname: Mariados
authors.affiliation: 21st Century Oncology, East Bradenton, Florida.
authors.forename: John
authors.initials: J
authors.lastname: Sylvester
authors.affiliation: Western New York Urology Associates, Cancer Care of WNY, Cheektowaga, New York.
authors.forename: Dhiren
authors.initials: D
authors.lastname: Shah
authors.affiliation: The Urology Center of Colorado, Denver, Colorado.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Karsh
authors.affiliation: Chesapeake Urology Research Associates, The Prostate Center, Owings Mills, Maryland.
authors.forename: Richard
authors.initials: R
authors.lastname: Hudes
authors.affiliation: Arizona Oncology Services Foundation, Phoenix, Arizona.
authors.forename: David
authors.initials: D
authors.lastname: Beyer
authors.affiliation: Urological Surgeons of Northern California, Campbell, California.
authors.forename: Steven
authors.initials: S
authors.lastname: Kurtzman
authors.affiliation: The Research Foundation of State University of New York, SUNY Upstate Medical University, Syracuse, New York.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Bogart
authors.affiliation: Peninsula Cancer Center, Poulsbo, Washington.
authors.forename: R Alex
authors.initials: RA
authors.lastname: Hsi
authors.affiliation: Urology Nevada, Reno, Nevada.
authors.forename: Michael
authors.initials: M
authors.lastname: Kos
authors.affiliation: University Hospitals Case Medical Center, Cleveland, Ohio.
authors.forename: Rodney
authors.initials: R
authors.lastname: Ellis
authors.affiliation: Sutter Health Sacramento Sierra Region, Sutter Institute for Medical Research, Sacramento, California.
authors.forename: Mark
authors.initials: M
authors.lastname: Logsdon
authors.affiliation: Advanced Radiation Centers of New York, Lake Success, New York.
authors.forename: Shawn
authors.initials: S
authors.lastname: Zimberg
authors.affiliation: Oregon Urology Institute, Springfield, Oregon.
authors.forename: Kevin
authors.initials: K
authors.lastname: Forsythe
authors.affiliation: University of Rochester, Rochester, New York.
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.affiliation: CentraState Medical Center, Freehold, New Jersey.
authors.forename: Edward
authors.initials: E
authors.lastname: Soffen
authors.affiliation: Carolina Regional Cancer Center, 21st Century Oncology, Myrtle Beach, South Carolina.
authors.forename: Patrick
authors.initials: P
authors.lastname: Francke
authors.affiliation: 21st Century Oncology, Fort Meyers, Florida.
authors.forename: Constantine
authors.initials: C
authors.lastname: Mantz
authors.affiliation: Emory University, Atlanta, Georgia.
authors.forename: Peter
authors.initials: P
authors.lastname: Rossi
authors.affiliation: The Johns Hopkins University, Baltimore, Maryland.
authors.forename: Theodore
authors.initials: T
authors.lastname: DeWeese
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Hamstra
authors.affiliation: Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Walter
authors.initials: W
authors.lastname: Bosch
authors.affiliation: Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Hiram
authors.initials: H
authors.lastname: Gay
authors.affiliation: Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Jeff
authors.initials: J
authors.lastname: Michalski
mesh_terms: D000368:Aged; D057918:Fiducial Markers; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000008:administration & dosage*; D008297:Male; D058958:Organs at Risk / Q000528:radiation effects*; D011446:Prospective Studies; D011467:Prostate; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D011788:Quality of Life; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000517:prevention & control*; D011835:Radiation Protection / Q000295:instrumentation*; D011859:Radiography; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided / Q000295:instrumentation* / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D012007:Rectum / Q000528:radiation effects*; D014551:Urinary Tract / Q000528:radiation effects
chemical_list: D020136:Hydrogel, Polyethylene Glycol Dimethacrylate