title: Image-guided IMRT for localized prostate cancer with daily repositioning: inferring the difference between planned dose and delivered dose distribution.
abstract: BACKGROUND
  To investigate the dosimetric impact of daily on-line repositioning during a full course of IMRT for prostate cancer.
  
  
  METHODS
  Twenty patients were treated with image-guided IMRT. Each pre-treatment plan (Plan A) was compared with a post-treatment plan sum (Plan B) based on couch shifts measured. The delivered dose to the prostate without a daily repositioning was inferred by considering each daily couch shift during the whole course of image-guided IMRT (i.e., plan B). Dose metrics were compared for prostate CTV (P-CTV) and PTV (P-PTV) and for organs at risk. Ten patients were treated with a 5 mm margin and 10 patients with a 10 mm margin.
  
  
  RESULTS
  For plan A vs. plan B: the average D95, D98, D50, D mean and EUD were: 76.4 Gy vs. 73.9 Gy (p = 0.0007), 75.4 Gy vs. 72.3 Gy (p = 0.001), 78.9 Gy vs. 78.4 Gy (p = 0.014), 78.7 Gy vs. 77.8 Gy (p = 0.003) and 78.1 Gy vs. 75.9 Gy (p = 0.002), respectively for P-CTV, and 73.2 Gy vs. 69.3 Gy (p = 0.0006), 70.7 Gy vs. 66.0 Gy (p = 0.0008), 78.3 Gy vs. 77.5 Gy (p = 0.001), 77.8 Gy vs. 76.4 Gy (p = 0.0002) and 74.4 Gy vs. 69.2 Gy (p = 0.003), respectively for P-PTV. Margin comparison showed no differences in dose metrics between the two plans except for D98 of the rectum in plan B which was significantly higher with a 10 mm margin.
  
  
  CONCLUSIONS
  The absence of daily image-guided IMRT resulted in a significantly less uniform and less homogeneous dose distribution to the prostate. A reduction in PTV margin showed neither a lower target coverage nor a better spare of OAR with and without daily image-guided IMRT.
authors.affiliation: Department of Radiation Oncology, Georges François Leclerc Cancer Center, 21000 Dijon, France.
authors.forename: A
authors.initials: A
authors.lastname: Arnaud
authors.affiliation: Department of Radiation Oncology, Georges François Leclerc Cancer Center, 21000 Dijon, France.
authors.forename: P
authors.initials: P
authors.lastname: Maingon
authors.affiliation: Department of Biostatistics, Georges François Leclerc Cancer Center, 21000 Dijon, France.
authors.forename: M
authors.initials: M
authors.lastname: Gauthier
authors.affiliation: Department of Radiation Oncology, Division of Medical Physics, Georges François Leclerc Cancer Center, 21000 Dijon, France.
authors.forename: S
authors.initials: S
authors.lastname: Naudy
authors.affiliation: Department of Radiation Oncology, Division of Medical Physics, Institut Curie, 75000 Paris, France.
authors.forename: J L
authors.initials: JL
authors.lastname: Dumas
authors.affiliation: Department of Radiation Oncology, Georges François Leclerc Cancer Center, 21000 Dijon, France.
authors.forename: E
authors.initials: E
authors.lastname: Martin
authors.affiliation: Department of Radiation Oncology, Georges François Leclerc Cancer Center, 21000 Dijon, France.
authors.forename: K
authors.initials: K
authors.lastname: Peignaux-Casasnovas
authors.affiliation: Department of Radiation Oncology, Georges François Leclerc Cancer Center, 21000 Dijon, France.
authors.forename: G
authors.initials: G
authors.lastname: Truc
authors.affiliation: Department of Biostatistics, Georges François Leclerc Cancer Center, 21000 Dijon, France.
authors.forename: F
authors.initials: F
authors.lastname: Bonnetain
authors.affiliation: Department of Radiation Oncology, Georges François Leclerc Cancer Center, 21000 Dijon, France. Electronic address: gcrehange@cgfl.fr.
authors.forename: G
authors.initials: G
authors.lastname: Crehange
mesh_terms: D006801:Humans; D008297:Male; D058958:Organs at Risk / Q000528:radiation effects; D056888:Patient Positioning; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D061089:Radiotherapy, Image-Guided / Q000009:adverse effects / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D013997:Time Factors
keywords: EUD; IMRT; On-line repositioning; Prostate cancer