title: Potential interest of developing an integrated boost dose escalation for stereotactic irradiation of primary prostate cancer.
abstract: BACKGROUND
  The stereotactic irradiation is a new approach for low-risk prostate cancer. The aim of the present study was to evaluate a schema of stereotactic irradiation of the prostate with an integrated-boost into the tumor.
  
  
  METHODS
  The prostate and the tumor were delineated by a radiologist on CT/MRI fusion. A 9-coplanar fields IMRT plan was optimized with three different dose levels: 1) 5 × 6.5 Gy to the PTV1 (plan 1), 2) 5 × 8 Gy to the PTV1 (plan 2) and 3) 5 × 6.5 Gy on the PTV1 with 5 × 8 Gy on the PTV2 (plan 3). The maximum dose (MaxD), mean dose (MD) and doses received by 2% (D2), 5% (D5), 10% (D10) and 25% (D25) of the rectum and bladder walls were used to compare the 3 IMRT plans.
  
  
  RESULTS
  A dose escalation to entire prostate from 6.5 Gy to 8 Gy increased the rectum MD, MaxD, D2, D5, D10 and D25 by 3.75 Gy, 8.42 Gy, 7.88 Gy, 7.36 Gy, 6.67 Gy and 5.54 Gy. Similar results were observed for the bladder with 1.72 Gy, 8.28 Gy, 7.01 Gy, 5.69 Gy, 4.36 Gy and 2.42 Gy for the same dosimetric parameters. An integrated SBRT boost only to PTV2 reduced by about 50% the dose difference for rectum and bladder compared to a homogenous prostate dose escalation. Thereby, the MD, D2, D5, D10 and D25 for rectum were increased by 1.51 Gy, 4.24 Gy, 3.08 Gy, 2.84 Gy and 2.37 Gy in plan 3 compared to plan 1.
  
  
  CONCLUSIONS
  The present planning study of an integrated SBRT boost limits the doses received by the rectum and bladder if compared to a whole prostate dose escalation for SBRT approach.
authors.affiliation: Department of Radiation Oncology, Centre Hospitalier Lyon Sud, Lyon-Pierre Benite, France; Department of Medical Physics, Centre Hospitalier Lyon Sud, Lyon-Pierre Benite, France.
authors.forename: C
authors.initials: C
authors.lastname: Udrescu
authors.affiliation: Department of Urological Radiology, Hopital Edouard Herriot, Lyon, France.
authors.forename: O
authors.initials: O
authors.lastname: Rouvière
authors.affiliation: Department of Radiation Oncology, Centre Hospitalier Lyon Sud, Lyon-Pierre Benite, France.
authors.forename: C
authors.initials: C
authors.lastname: Enachescu
authors.affiliation: Department of Medical Physics, Centre Hospitalier Lyon Sud, Lyon-Pierre Benite, France.
authors.forename: M-P
authors.initials: MP
authors.lastname: Sotton
authors.affiliation: Department of Radiology, Centre Hospitalier Lyon Sud, Lyon-Pierre Benite, France.
authors.forename: J
authors.initials: J
authors.lastname: Bouffard-Vercelli
authors.affiliation: Department of Medical Physics, Centre Hospitalier Lyon Sud, Lyon-Pierre Benite, France.
authors.forename: P
authors.initials: P
authors.lastname: Jalade
authors.affiliation: Department of Radiation Oncology, Centre Hospitalier Lyon Sud, Lyon-Pierre Benite, France. Electronic address: olivier.chapet@chu-lyon.fr.
authors.forename: O
authors.initials: O
authors.lastname: Chapet
mesh_terms: D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D058958:Organs at Risk / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery*; D011829:Radiation Dosage; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed
keywords: IMRT; Integrated boost; Prostate cancer; Stereotactic body radiotherapy