title: Anterior myocardial territory may replace the heart as organ at risk in intensity-modulated radiotherapy for left-sided breast cancer.
abstract: OBJECTIVE
  We investigated whether the heart could be replaced by the anterior myocardial territory (AMT) as the organ at risk (OAR) in intensity-modulated radiotherapy (IMRT) of the breast for patients with left-sided breast cancer.
  
  
  METHODS
  Twenty-three patients with left-sided breast cancer who received postoperative radiation after breast-conserving surgery were studied. For each patient, we generated five IMRT plans including heart (H), left ventricle (LV), AMT, LV+AMT, and H+LV as the primary OARs, respectively, except both lungs and right breast, which corresponded to IMRT(H), IMRT(LV), IMRT(AMT), IMRT(LV+AMT), and IMRT(H+LV). For the planning target volumes and OARs, the parameters of dose-volume histograms were compared.
  
  
  RESULTS
  The homogeneity index, conformity index, and coverage index were not compromised significantly in IMRT(AMT), IMRT(LV) and IMRT(LV+ AMT), respectively, when compared with IMRT(H). The mean dose to the heart, LV, and AMT decreased 5.3-21.5% (p < 0.05), 19.9-29.5% (p < 0.05), and 13.3-24.5% (p < 0.05), respectively. Similarly, the low (e.g., V5%), middle (e.g., V20%), and high (e.g., V30%) dose-volume of the heart, LV, and AMT decreased with different levels. The mean dose and V10% of the right lung increased by 9.2% (p < 0.05) and 27.6% (p < 0.05), respectively, in IMRT(LV), and the mean dose and V5% of the right breast decreased significantly in IMRT(AMT) and IMRT(LV+AMT). IMRT(AMT) was the preferred plan and was then compared with IMRT(H+LV); the majority of dose-volume histogram parameters of OARs including the heart, LV, AMT, both lungs, and the right breast were not statistically different. However, the low dose-volume of LV increased and the middle dose-volume decreased significantly (p < 0.05) in IMRT(AMT). Also, those of the right lung (V10%, V15%) and right breast (V5%, V10%) decreased significantly (p < 0.05).
  
  
  CONCLUSIONS
  The AMT may replace the heart as the OAR in left-sided breast IMRT after breast-conserving surgery to decrease the radiation dose to the heart.
authors.affiliation: Department of Radiotherapy, Hubei Cancer Hospital, Wuhan, P.R. China.
authors.forename: Wenyong
authors.initials: W
authors.lastname: Tan
authors.forename: Dong
authors.initials: D
authors.lastname: Liu
authors.forename: Chenbin
authors.initials: C
authors.lastname: Xue
authors.forename: Jiaozhen
authors.initials: J
authors.lastname: Xu
authors.forename: Beihui
authors.initials: B
authors.lastname: Li
authors.forename: Zhengwang
authors.initials: Z
authors.lastname: Chen
authors.forename: Desheng
authors.initials: D
authors.lastname: Hu
authors.forename: Xionghong
authors.initials: X
authors.lastname: Wang
mesh_terms: D001940:Breast / Q000528:radiation effects; D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D006321:Heart / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000528:radiation effects*; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000528:radiation effects; D015412:Mastectomy, Segmental; D009206:Myocardium; D058958:Organs at Risk / Q000528:radiation effects*; D011832:Radiation Injuries / Q000517:prevention & control*; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*