title: A multicentre study of the evidence for customized margins in photon breast boost radiotherapy.
abstract: OBJECTIVE
  To determine if subsets of patients may benefit from smaller or larger margins when using laser setup and bony anatomy verification of breast tumour bed (TB) boost radiotherapy (RT).
  
  
  METHODS
  Verification imaging data acquired using cone-beam CT, megavoltage CT or two-dimensional kilovoltage imaging on 218 patients were used (1574 images). TB setup errors for laser-only setup (dlaser) and for bony anatomy verification (dbone) were determined using clips implanted into the TB as a gold standard for the TB position. Cases were grouped by centre-, patient- and treatment-related factors, including breast volume, TB position, seroma visibility and surgical technique. Systematic (Σ) and random (σ) TB setup errors were compared between groups, and TB planning target volume margins (MTB) were calculated.
  
  
  RESULTS
  For the study population, Σlaser was between 2.8 and 3.4 mm, and Σbone was between 2.2 and 2.6 mm, respectively. Females with larger breasts (p = 0.03), easily visible seroma (p ≤ 0.02) and open surgical technique (p ≤ 0.04) had larger Σlaser. Σbone was larger for females with larger breasts (p = 0.02) and lateral tumours (p = 0.04). Females with medial tumours (p < 0.01) had smaller Σbone.
  
  
  CONCLUSIONS
  If clips are not used, margins should be 8 and 10 mm for bony anatomy verification and laser setup, respectively. Individualization of TB margins may be considered based on breast volume, TB and seroma visibility.
  
  
  CONCLUSIONS
  Setup accuracy using lasers and bony anatomy is influenced by patient and treatment factors. Some patients may benefit from clip-based image guidance more than others.
authors.affiliation: 1 Radiotherapy and Imaging, Institute of Cancer Research Sutton, UK.
authors.forename: Emma J
authors.initials: EJ
authors.lastname: Harris
authors.affiliation: 2 Oncology Centre, Cambridge University Hospital NHS Foundation Trust, Cambridge, UK.|3 Oncology Centre, Colchester Hospital University NHS Trust, Colchester, UK.
authors.forename: Mukesh B
authors.initials: MB
authors.lastname: Mukesh
authors.affiliation: 4 The Breast Unit, Royal Marsden Hospital NHS Foundation Trust, Sutton, UK.
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Donovan
authors.affiliation: 4 The Breast Unit, Royal Marsden Hospital NHS Foundation Trust, Sutton, UK.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Kirby
authors.affiliation: 5 ICR-CTSU, Institute of Cancer Research, Sutton, UK.|6 Macmillan Survivorship Research Group, Faculty of Health Sciences, University of Southampton, UK.
authors.forename: Joanne S
authors.initials: JS
authors.lastname: Haviland
authors.affiliation: 2 Oncology Centre, Cambridge University Hospital NHS Foundation Trust, Cambridge, UK.
authors.forename: Raj
authors.initials: R
authors.lastname: Jena
authors.affiliation: 1 Radiotherapy and Imaging, Institute of Cancer Research Sutton, UK.
authors.forename: John
authors.initials: J
authors.lastname: Yarnold
authors.affiliation: 7 Department of Physics, The Clatterbridge Cancer Centre NHS Foundation Trust, Wirral, UK.
authors.forename: Angela
authors.initials: A
authors.lastname: Baker
authors.affiliation: 2 Oncology Centre, Cambridge University Hospital NHS Foundation Trust, Cambridge, UK.
authors.forename: June
authors.initials: J
authors.lastname: Dean
authors.affiliation: 4 The Breast Unit, Royal Marsden Hospital NHS Foundation Trust, Sutton, UK.
authors.forename: Sally
authors.initials: S
authors.lastname: Eagle
authors.affiliation: 7 Department of Physics, The Clatterbridge Cancer Centre NHS Foundation Trust, Wirral, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Mayles
authors.affiliation: 5 ICR-CTSU, Institute of Cancer Research, Sutton, UK.
authors.forename: Claire
authors.initials: C
authors.lastname: Griffin
authors.affiliation: 8 Department of Radiotherapy, Ipswich Hospital NHS Trust, Ipswich, UK.
authors.forename: Rosalind
authors.initials: R
authors.lastname: Perry
authors.affiliation: 9 Radiotherapy Department, Peterborough City Hospital, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Poynter
authors.affiliation: 2 Oncology Centre, Cambridge University Hospital NHS Foundation Trust, Cambridge, UK.
authors.forename: Charlotte E
authors.initials: CE
authors.lastname: Coles
authors.affiliation: 10 CVSSP, University of Surrey, Guildford, UK.
authors.forename: Philip M
authors.initials: PM
authors.lastname: Evans
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D005260:Female; D006801:Humans; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D056888:Patient Positioning; D017785:Photons; D011857:Radiographic Image Interpretation, Computer-Assisted; D011880:Radiotherapy Planning, Computer-Assisted; D061106:Radiotherapy Setup Errors / Q000517:prevention & control*; D061089:Radiotherapy, Image-Guided; D006113:United Kingdom