title: Does mean heart dose sufficiently reflect coronary artery exposure in left-sided breast cancer radiotherapy? : Influence of respiratory gating.
abstract: OBJECTIVE
  With extensive use of systemic treatment, the issue of cardiac mortality after breast cancer radiation (RT) is still important. The aim of our analysis was to clarify whether the dose to one surrogate parameter (e. g., mean heart dose, as used in most studies) reflects the dose to the other cardiovascular structures especially the left anterior descending artery depending on breathing-adapted RT.
  
  
  METHODS
  A total of 130 patients who underwent adjuvant RT (50.4 Gy plus boost 9-16 Gy) were evaluated. In all, 71 patients were treated with free-breathing and 59 patients using respiratory monitoring (gated RT). Dosimetric associations were calculated.
  
  
  RESULTS
  The mean dose to the heart (Dmean heart) was reduced from 2.7 (0.8-5.2) Gy to 2.4 (1.1-4.6) Gy, the Dmean LAD (left anterior descending artery) decreased from 11.1 (1.3-28.6) Gy to 9.3 (2.2-19.9) Gy with gated RT (p = 0.04). A significant relationship was shown for Dmean heart-Dmean LAD, V25heart-Dmean LAD and Dmax heart-Dmax LAD for gated patients only (p < 0.01). For every 1 Gy increase in Dmean heart, mean LAD doses rose by 3.6 Gy, without gating V25 ≤5 % did not assure a benefit and resulted in Dmean LAD between 1.3 and 28.6 Gy.
  
  
  CONCLUSIONS
  A significant reduction and association of heart and coronary artery (LAD) doses using inspiratory gating was shown. However, in free-breathing plans commonly measured dose constraints do not allow precise estimation of the dose to the coronary arteries.
authors.affiliation: Department of Radiotherapy and Radio-Oncology, Klinikum Braunschweig, Celler Straße 38, 38114, Braunschweig, Germany. m.schiebe@klinikum-braunschweig.de.|Radiation Oncology, Hannover Medical School, Hannover, Germany. m.schiebe@klinikum-braunschweig.de.
authors.forename: Martina
authors.identifier: http://orcid.org/0000-0002-3969-3735
authors.initials: M
authors.lastname: Becker-Schiebe
authors.affiliation: Department of Gynecology and Obstetrics, Klinikum Braunschweig, Braunschweig, Germany.
authors.forename: Maxi
authors.initials: M
authors.lastname: Stockhammer
authors.affiliation: Department of Radiotherapy and Radio-Oncology, Klinikum Braunschweig, Celler Straße 38, 38114, Braunschweig, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hoffmann
authors.affiliation: Department of Radiotherapy and Radio-Oncology, Klinikum Braunschweig, Celler Straße 38, 38114, Braunschweig, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Wetzel
authors.affiliation: Department of Gynecology and Obstetrics, Klinikum Braunschweig, Braunschweig, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Franz
mesh_terms: D000328:Adult; D000368:Aged; D003331:Coronary Vessels / Q000528:radiation effects*; D005260:Female; D006321:Heart / Q000528:radiation effects*; D006801:Humans; D008875:Middle Aged; D000069079:Radiation Exposure / Q000032:analysis*; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D015203:Reproducibility of Results; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D000069584:Unilateral Breast Neoplasms / Q000532:radiotherapy*
keywords: Adjuvant radiotherapy; Adverse effects; Breast-conserving therapy; Cardiac toxicity; Myocardial ischemia