title: Large breast size as a risk factor for late adverse effects of breast radiotherapy: is residual dose inhomogeneity, despite 3D treatment planning and delivery, the main explanation?
abstract: OBJECTIVE
  Large breast size is associated with an increased risk of late adverse effects after breast conservation surgery and radiotherapy, even when 3D dosimetry is used. The purpose of this study is to test the hypothesis that residual dose inhomogeneity is sufficient to explain the association.
  
  
  METHODS
  Patients previously treated after breast conservation surgery with whole breast radiotherapy using 3D dosimetry and followed up in the UK FAST hypofractionation trial were selected for this analysis. The residual level of dose inhomogeneity across the whole breast treatment volume was used to test for association between residual dosimetry and post-treatment change in breast appearance at 2 years post-radiotherapy.
  
  
  RESULTS
  At 2 years, 201/279 (72%) of women had no change in photographic breast appearance, 61 (22%) had mild change and 17 (6%) had marked change. Breast size and dosimetry were both significantly associated with late effects in univariate analyses, but only breast size remained an independent significant risk factor for change in breast appearance when included in a multiple regression model together with other prognostic factors (p=0.006 for trend).
  
  
  CONCLUSIONS
  Large-breasted women are more likely to suffer change in breast size and shape after whole breast radiotherapy delivered using 3D dosimetry, but residual dose inhomogeneity is insufficient to explain the association.
authors.affiliation: Department of Radiotherapy, The Royal Marsden NHS Foundation Trust, London, UK. Christy.Goldsmith@rmh.nhs.uk
authors.forename: Christy
authors.initials: C
authors.lastname: Goldsmith
authors.forename: Joanne
authors.initials: J
authors.lastname: Haviland
authors.forename: Yat
authors.initials: Y
authors.lastname: Tsang
authors.forename: Mark
authors.initials: M
authors.lastname: Sydenham
authors.forename: John
authors.initials: J
authors.lastname: Yarnold
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001940:Breast / Q000473:pathology*; D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008875:Middle Aged; D010781:Photography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012307:Risk Factors