title: Reduction of rectal dose by integration of the boost in the large-field treatment plan for prostate irradiation.
abstract: OBJECTIVE
  To reduce the dose in the rectal wall from prostate irradiation at high dose levels.
  
  
  METHODS
  Treatment plans in which the boost fields were integrated into the large fields (simultaneous integrated boost [SIB]) were compared with plans in which the large fields and boost fields were planned individually and applied in a sequential manner (sequential boost). Two target volumes were delineated: PTV1, the target volume of the large fields that is irradiated to 68 Gy, and PTV2, the target volume of the boost fields that is irradiated to 10 Gy. The sequential boost and the SIB were normalized to the mean dose in PTV2, being 78 Gy. We used a five-field intensity-modulated radiotherapy (IMRT) technique, applied in a step and shoot mode, and included beam weight optimization. A set of 5 patients with varying degree of overlap between PTV1 and the rectal wall was used for analysis.
  
  
  RESULTS
  The SIB resulted in a reduction of the dose in the rectal wall. Rectal normal tissue complication probability (NTCP) decreased for the SIB, on average, by a factor of almost 2, compared with the sequential boost.
  
  
  CONCLUSIONS
  The SIB reduced the dose in the rectal wall, compared with the sequential boost technique.
authors.affiliation: Radiotherapy Division, The Netherlands Cancer Institute/Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands.
authors.forename: Luc J
authors.initials: LJ
authors.lastname: Bos
authors.forename: Eugène M F
authors.initials: EM
authors.lastname: Damen
authors.forename: Roel W
authors.initials: RW
authors.lastname: de Boer
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Mijnheer
authors.forename: Daniel L
authors.initials: DL
authors.lastname: McShan
authors.forename: Benedick A
authors.initials: BA
authors.lastname: Fraass
authors.forename: Marc L
authors.initials: ML
authors.lastname: Kessler
authors.forename: Joos V
authors.initials: JV
authors.lastname: Lebesque
mesh_terms: D000230:Adenocarcinoma / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D009426:Netherlands; D055585:Physical Phenomena; D010825:Physics; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000517:prevention & control*; D011835:Radiation Protection; D012007:Rectum