title: Setup accuracy for prone and supine whole breast irradiation.
abstract: OBJECTIVE
  To evaluate cone-beam computed tomography (CBCT) based setup accuracy and margins for prone and supine whole breast irradiation (WBI).
  
  
  METHODS
  Setup accuracy was evaluated on 3559 CBCT scans of 242 patients treated with WBI and uncertainty margins were calculated using the van Herk formula. Uni- and multivariate analysis on individual margins was performed for age, body mass index (BMI) and cup size.
  
  
  RESULTS
  The population-based margin in vertical (VE), lateral (LA) and longitudinal (LO) directions was 10.4/9.4/9.4 mm for the 103 supine and 10.5/22.4/13.7 mm for the 139 prone treated patients, being significantly (p < 0.01) different for the LA and LO directions. Multivariate analysis identified a significant (p < 0.05) correlation between BMI and the LO margin in supine position and the VE/LA margin in prone position.
  
  
  CONCLUSIONS
  In this series, setup accuracy is significantly worse in prone compared to supine position for the LA and LO directions. However, without proper image-guidance, uncertainty margins of about 1 cm are also necessary for supine WBI. For patients with a higher BMI, larger margins are required.
authors: Department of Radiotherapy, University Hospital Ghent, De Pintelaan 185, 9000, Ghent, Belgium.
authors: Thomas
authors: T
authors: Mulliez
authors: Department of Radiotherapy, University Hospital Ghent, De Pintelaan 185, 9000, Ghent, Belgium.|Department of Radiotherapy, University Hospital Liege, Liege, Belgium.
authors: Akos
authors: A
authors: Gulyban
authors: Department of Radiotherapy, University Hospital Ghent, De Pintelaan 185, 9000, Ghent, Belgium.
authors: Tom
authors: T
authors: Vercauteren
authors: Department of Radiotherapy, University Hospital Ghent, De Pintelaan 185, 9000, Ghent, Belgium.
authors: Annick
authors: A
authors: van Greveling
authors: Department of Radiotherapy, University Hospital Ghent, De Pintelaan 185, 9000, Ghent, Belgium.
authors: Bruno
authors: B
authors: Speleers
authors: Department of Radiotherapy, University Hospital Ghent, De Pintelaan 185, 9000, Ghent, Belgium.
authors: Wilfried
authors: W
authors: De Neve
authors: Department of Radiotherapy, University Hospital Ghent, De Pintelaan 185, 9000, Ghent, Belgium. liv.veldeman@uzgent.be.
authors: Liv
authors: L
authors: Veldeman
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D015331:Cohort Studies; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D005260:Female; D006801:Humans; D008875:Middle Aged; D056888:Patient Positioning; D016684:Prone Position; D011446:Prospective Studies; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061106:Radiotherapy Setup Errors / Q000517:prevention & control*; D012189:Retrospective Studies; D016683:Supine Position
keywords: Breast radiotherapy; Cone-beam computed tomography; Prone position; Setup accuracy; Supine position