title: Dosimetric implications of an injection of hyaluronic acid for preserving the rectal wall in prostate stereotactic body radiation therapy.
abstract: OBJECTIVE
  This study assessed the contribution of ahyaluronic acid (HA) injection between the rectum and the prostate to reducing the dose to the rectal wall in stereotactic body radiation therapy (SBRT).
  
  
  METHODS
  As part of a phase 2 study of hypofractionated radiation therapy (62 Gy in 20 fractions), the patients received a transperineal injection of 10 cc HA between the rectum and the prostate. A dosimetric computed tomographic (CT) scan was systematically performed before (CT1) and after (CT2) the injection. Two 9-beam intensity modulated radiation therapy-SBRT plans were optimized for the first 10 patients on both CTs according to 2 dosage levels: 5 × 6.5 Gy (PlanA) and 5 × 8.5 Gy (PlanB). Rectal wall parameters were compared with a dose-volume histogram, and the prostate-rectum separation was measured at 7 levels of the prostate on the center line of the organ.
  
  
  RESULTS
  For both plans, the average volume of the rectal wall receiving the 90% isodose line (V90%) was reduced up to 90% after injection. There was no significant difference (P=.32) between doses received by the rectal wall on CT1 and CT2 at the base of the prostate. This variation became significant from the median plane to the apex of the prostate (P=.002). No significant differences were found between PlanA without HA and PlanB with HA for each level of the prostate (P=.77, at the isocenter of the prostate).
  
  
  CONCLUSIONS
  HA injection significantly reduced the dose to the rectal wall and allowed a dose escalation from 6.5 Gy to 8.5 Gy without increasing the dose to the rectum. A phase 2 study is under way in our department to assess the rate of acute and late rectal toxicities when SBRT (5 × 8.5 Gy) is combined with an injection of HA.
authors.affiliation: Department of Radiation Oncology, Centre Hospitalier Lyon Sud, Pierre Benite, France. Electronic address: olivier.chapet@chu-lyon.fr.
authors.forename: Olivier
authors.initials: O
authors.lastname: Chapet
authors.affiliation: Department of Radiation Oncology, Centre Hospitalier Lyon Sud, Pierre Benite, France; Department of Medical Physics, Centre Hospitalier Lyon Sud, Pierre Benite, France.
authors.forename: Corina
authors.initials: C
authors.lastname: Udrescu
authors.affiliation: Department of Radiation Oncology, Centre Hospitalier Lyon Sud, Pierre Benite, France.
authors.forename: Ronan
authors.initials: R
authors.lastname: Tanguy
authors.affiliation: Department of Urology, Centre Hospitalier Lyon Sud, Pierre Benite, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Ruffion
authors.affiliation: Department of Radiation Oncology, Centre Val d'Aurelle, Montpellier, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Fenoglietto
authors.affiliation: Department of Medical Physics, Centre Hospitalier Lyon Sud, Pierre Benite, France.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Sotton
authors.affiliation: Department of Urology, Centre Hospitalier Lyon Sud, Pierre Benite, France.
authors.forename: Marian
authors.initials: M
authors.lastname: Devonec
authors.affiliation: Department of Urology, Hopital Edouard Herriot, Lyon, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Colombel
authors.affiliation: Department of Medical Physics, Centre Hospitalier Lyon Sud, Pierre Benite, France.
authors.forename: Patrice
authors.initials: P
authors.lastname: Jalade
authors.affiliation: Department of Radiation Oncology, Centre Val d'Aurelle, Montpellier, France.
authors.forename: David
authors.initials: D
authors.lastname: Azria
mesh_terms: D019583:Dose Fractionation, Radiation; D006801:Humans; D006820:Hyaluronic Acid / Q000008:administration & dosage*; D008297:Male; D059351:Organ Sparing Treatments / Q000379:methods*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D011832:Radiation Injuries / Q000517:prevention & control*; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D012007:Rectum / Q000000981:diagnostic imaging / Q000528:radiation effects*; D014057:Tomography, X-Ray Computed / Q000379:methods; D047368:Tumor Burden; D055675:Viscosupplements / Q000008:administration & dosage*
chemical_list: D055675:Viscosupplements; D006820:Hyaluronic Acid