title: Anatomic features of interest in women at risk of cardiac exposure from whole breast radiotherapy.
abstract: OBJECTIVE
  Left-sided breast radiotherapy (RT) can result in cardiac exposure. This study aims to identify predictive anatomic features in women requiring breath-hold (RT(BH)) for cardiac sparing during adjuvant whole breast RT.
  
  
  METHODS
  We retrospectively reviewed free-breathing (FB) CT scans of 80 women previously treated with left-sided breast RT. Unfavourable cardiac anatomy was defined as the number of consecutive axial CT slices (2 mm) in which the anterior chest wall contacted the heart (Contact(Heart)) or left ventricle (Contact(LV)). The sternal angle and Haller Index (HI) were used to measure chest concavity. Position and volume of post-operative cavity was also quantified.
  
  
  RESULTS
  Heart mean dose (D(mean)) was strongly correlated with Contact(LV) (r=0.625, p<0.001) and Contact(Heart) (r=0.524, p<0.001) but not significantly correlated with tumor size, cavity volume, heart volume, cavity distance to chest wall, sternal angle, or HI. ROC analysis of Contact(Heart) was most predictive of the need for breath-hold (RT(BH)) technique [Area Under Curve=0.815 (SE: 0.048; 95% CI: 0.721-0.91)] and ⩾25 Contact(Heart) CT slices predicted for heart D(mean) ⩾1.7 Gy (68% sensitivity and 82% specificity).
  
  
  CONCLUSIONS
  Contact(Heart) on FB CT of ⩾25 axial slices (2 mm), ⩾50 mm of para-sagittal heart contact, was predictive of higher heart D(mean) and suggest a potential need for RT(BH).
authors.affiliation: Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Canada.
authors.forename: Grace
authors.initials: G
authors.lastname: Lee
authors.affiliation: Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Canada; Department of Radiation Oncology, University of Toronto, Canada.
authors.forename: Tara
authors.initials: T
authors.lastname: Rosewall
authors.affiliation: Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Canada; Department of Radiation Oncology, University of Toronto, Canada.
authors.forename: Anthony
authors.initials: A
authors.lastname: Fyles
authors.affiliation: Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Canada; Department of Radiation Oncology, University of Toronto, Canada.
authors.forename: Nicole
authors.initials: N
authors.lastname: Harnett
authors.affiliation: Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Canada; Department of Radiation Oncology, University of Toronto, Canada. Electronic address: rob.dinniwell@rmp.uhn.on.ca.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Dinniwell
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D062485:Breath Holding; D005260:Female; D006321:Heart / Q000528:radiation effects*; D006801:Humans; D008875:Middle Aged; D018714:Radiotherapy, Adjuvant / Q000379:methods; D035441:Thoracic Wall / Q000528:radiation effects; D014057:Tomography, X-Ray Computed
keywords: Breast cancer; Breath-hold; Cardiac sparing; Heart dose; Radiotherapy