title: First report of transperineal polyethylene glycol hydrogel spacer use to curtail rectal radiation dose after permanent iodine-125 prostate brachytherapy.
abstract: OBJECTIVE
  To demonstrate the feasibility of transperineal polyethylene glycol (PEG) hydrogel insertion into anterior perirectal fat for reducing rectal radiation dose in patients with suboptimal rectal dosimetry after permanent iodine-125 prostate brachytherapy.
  
  
  METHODS
  Five patients with suboptimal rectal dosimetry after iodine-125 seed brachytherapy implant underwent a single transperineal injection of PEG hydrogel into the anterior perirectal fat under general anesthetic using transrectal ultrasound guidance. Prostate-rectum separation and rectal radiation dose before and after PEG hydrogel spacer insertion were measured. Toxicity because of spacer insertion was assessed at Days 0-1 and 4-6 weeks using National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0.
  
  
  RESULTS
  All patients experienced a clinically significant reduction in the volume of rectum receiving greater than or equal to the prescription dose (RV100) on the postspacer postimplant dosimetry, compared with the prespacer postimplant dosimetry. Mean prostate-rectum separation that was achieved with the insertion of the spacer was 15.1 mm (±3.4). The mean difference in separation from before to after spacer insertion was 12.5 mm (±4.5). This was associated with a reduction in mean RV100 from 3.04 (±1.2) to 0.06 (±0.1) cc. Toxicities were limited to Grade 1 (National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0) perineal pain and rectal discomfort (3/5 patients). There were no Grade 2 or greater toxicities reported after insertion of the spacer.
  
  
  CONCLUSIONS
  PEG hydrogel is safe and effective at reducing rectal radiation dose in select patients with suboptimal rectal dosimetry after prostate seed brachytherapy.
authors: Department of Radiation Oncology, St George Hospital, Kogarah, New South Wales, Australia. nadine.beydoun@sesiahs.health.nsw.gov.au
authors: Nadine
authors: N
authors: Beydoun
authors: Joseph A
authors: JA
authors: Bucci
authors: Yaw S
authors: YS
authors: Chin
authors: David
authors: D
authors: Malouf
authors: Ese
authors: E
authors: Enari
authors: Samuel D
authors: SD
authors: Painter
mesh_terms: D000368:Aged; D001918:Brachytherapy / Q000379:methods*; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D011092:Polyethylene Glycols; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D012007:Rectum / Q000000981:diagnostic imaging; D014463:Ultrasonography
chemical_list: D007457:Iodine Radioisotopes; D011092:Polyethylene Glycols