title: Comparison of two different rectal spacers in prostate cancer external beam radiotherapy in terms of rectal sparing and volume consistency.
abstract: OBJECTIVE
  In external beam radiation (EBRT) of the prostate, the rectum is the dose-limiting organ at risk, and sparing of the anterior rectal wall is a prerequisite for safe delivery of doses beyond 70 Gy. Spatial sparing of the rectum can be achieved by introducing a spacer material into the retroprostatic space, thus separating the anterior rectal wall from the PTV.
  
  
  METHODS
  Two spacer technologies, Spacer OAR, a polyethylene glycol gel and ProSpace, a saline inflated balloon, were compared in terms of spacer volume, stability, and dose reduction to the anterior rectum wall in 78 patients.
  
  
  RESULTS
  Both spacer systems significantly reduced the rectum surface encompassed by the 95% isodose (gel: -35%, p<0.01; balloon -63.4%, p<0.001) compared to a control group. The balloon spacer was superior in reducing rectum dose (-27.7%, p=0.034), but exhibited an average volume loss of >50% during the full course of treatment of 37-40 fractions, while the volume of gel spacers remained fairly constant.
  
  
  CONCLUSIONS
  In choosing between the two spacer technologies, the advantageous dose reduction of the balloon needs to be weighed up against the better volume consistency of the gel spacer with respect to the duration of hypofractionated vs normofractionated regimens.
authors.affiliation: Dpt. of Radiation Oncology, St. Johanns-Spital, Paracelsus Medical University of Salzburg, Austria. Electronic address: f.wolf@salk.at.
authors.forename: Frank
authors.initials: F
authors.lastname: Wolf
authors.affiliation: Dpt. of Radiation Oncology, St. Johanns-Spital, Paracelsus Medical University of Salzburg, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Gaisberger
authors.affiliation: Dpt. of Radiation Oncology, St. Johanns-Spital, Paracelsus Medical University of Salzburg, Austria.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Ziegler
authors.affiliation: Salzburg University of Applied Sciences, Paracelsus Medical University of Salzburg, Austria.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Krenn
authors.affiliation: Dpt. of Radiation Oncology, St. Johanns-Spital, Paracelsus Medical University of Salzburg, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Scherer
authors.affiliation: Dpt. of Urology, St. Johanns-Spital, Paracelsus Medical University of Salzburg, Austria.
authors.forename: Stephan
authors.initials: S
authors.lastname: Hruby
authors.affiliation: Dpt. of Urology, St. Johanns-Spital, Paracelsus Medical University of Salzburg, Austria.
authors.forename: Tobias
authors.initials: T
authors.lastname: Schätz
authors.affiliation: Dpt. of Radiology, St. Johanns-Spital, Paracelsus Medical University of Salzburg, Austria.
authors.forename: Rosemarie
authors.initials: R
authors.lastname: Forstner
authors.affiliation: Dept. of Surgery, St. Johanns-Spital, Paracelsus Medical University of Salzburg, Austria.
authors.forename: Josef
authors.initials: J
authors.lastname: Holzinger
authors.affiliation: Dpt. of Radiation Oncology, St. Johanns-Spital, Paracelsus Medical University of Salzburg, Austria.
authors.forename: Andrea
authors.initials: A
authors.lastname: Vaszi
authors.affiliation: Dpt. of Radiation Oncology, St. Johanns-Spital, Paracelsus Medical University of Salzburg, Austria.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Kametriser
authors.affiliation: Institute for Research and Development on Advanced Radiation Technologies (radART), St. Johanns-Spital, Paracelsus Medical University of Salzburg, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Steininger
authors.affiliation: Dpt. of Radiation Oncology, St. Johanns-Spital, Paracelsus Medical University of Salzburg, Austria; Institute for Research and Development on Advanced Radiation Technologies (radART), St. Johanns-Spital, Paracelsus Medical University of Salzburg, Austria.
authors.forename: Heinz
authors.initials: H
authors.lastname: Deutschmann
authors.affiliation: Dpt. of Radiation Oncology, St. Johanns-Spital, Paracelsus Medical University of Salzburg, Austria; Institute for Research and Development on Advanced Radiation Technologies (radART), St. Johanns-Spital, Paracelsus Medical University of Salzburg, Austria.
authors.forename: Felix
authors.initials: F
authors.lastname: Sedlmayer
mesh_terms: D019583:Dose Fractionation, Radiation; D006801:Humans; D008297:Male; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011835:Radiation Protection; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012007:Rectum / Q000528:radiation effects*
keywords: Balloon; Dose escalation; Hypofractionation; Prostate; Rectal sparing; Spacer