title: Cardiac dose reduction with deep inspiration breath hold for left-sided breast cancer radiotherapy patients with and without regional nodal irradiation.
abstract: BACKGROUND
  Deep inspiration breath hold (DIBH) reduces heart and left anterior descending artery (LAD) dose during left-sided breast radiation therapy (RT); however there is limited information about which patients derive the most benefit from DIBH. The primary objective of this study was to determine which patients benefit the most from DIBH by comparing percent reduction in mean cardiac dose conferred by DIBH for patients treated with whole breast RT ± boost (WBRT) versus those receiving breast/chest wall plus regional nodal irradiation, including internal mammary chain (IMC) nodes (B/CWRT + RNI) using a modified wide tangent technique. A secondary objective was to determine if DIBH was required to meet a proposed heart dose constraint of Dmean < 4 Gy in these two cohorts.
  
  
  METHODS
  Twenty consecutive patients underwent CT simulation both free breathing (FB) and DIBH. Patients were grouped into two cohorts: WBRT (n = 11) and B/CWRT + RNI (n = 9). 3D-conformal plans were developed and FB was compared to DIBH for each cohort using Wilcoxon signed-rank tests for continuous variables and McNemar's test for discrete variables. The percent relative reduction conferred by DIBH in mean heart and LAD dose, as well as lung V20 were compared between the two cohorts using Wilcox rank-sum testing. The significance level was set at 0.05 with Bonferroni correction for multiple testing.
  
  
  RESULTS
  All patients had comparable target coverage on DIBH and FB. DIBH statistically significantly reduced mean heart and LAD dose for both cohorts. Percent reduction in mean heart and LAD dose with DIBH was significantly larger in the B/CWRT + RNI cohort compared to WBRT group (relative reduction in mean heart and LAD dose: 55.9 % and 72.1 % versus 29.2 % and 43.5 %, p < 0.02). All patients in the WBRT group and five patients (56 %) in the B/CWBRT + RNI group met heart Dmean <4 Gy with FB. All patients met this constraint with DIBH.
  
  
  CONCLUSIONS
  All patients receiving WBRT met Dmean Heart < 4 Gy on FB, while only slightly over half of patients receiving B/CWRT + RNI were able to meet this constraint in FB. DIBH allowed a greater reduction in mean heart and LAD dose in patients receiving B/CWRT + RNI, including IMC nodes than patients receiving WBRT. These findings suggest greatest benefit from DIBH treatment for patients receiving regional nodal irradiation.
authors.affiliation: Division of Radiation Oncology, Department of Oncology, University of Calgary,, 2500 University Dr NW, Calgary, Alberta, T2N 1 N4, Canada. Rosanna.Yeung@albertahealthservices.ca.
authors.forename: Rosanna
authors.initials: R
authors.lastname: Yeung
authors.affiliation: Department of Medical Physics, Tom Baker Cancer Centre, 1331 29 Street Northwest, Calgary, AB, T2N 4 N2, Canada. Leigh.Conroy@albertahealthservices.ca.|Department of Physics & Astronomy, University of Calgary, 2500 University Dr NW, Calgary, Alberta, T2N 1 N4, Canada. Leigh.Conroy@albertahealthservices.ca.
authors.forename: Leigh
authors.initials: L
authors.lastname: Conroy
authors.affiliation: Department of Radiation Therapy, Tom Baker Cancer Centre, 1331 29 Street Northwest, Calgary, AB, T2N 4 N2, Canada. Karen.Long2@albertahealthservices.ca.
authors.forename: Karen
authors.initials: K
authors.lastname: Long
authors.affiliation: Department of Radiation Therapy, Tom Baker Cancer Centre, 1331 29 Street Northwest, Calgary, AB, T2N 4 N2, Canada. Daphne.Walrath@albertahealthservices.ca.
authors.forename: Daphne
authors.initials: D
authors.lastname: Walrath
authors.affiliation: Departments of Oncology and Community Health Sciences, University of Calgary, 2500 University Dr NW, Calgary, Alberta, T2N 1 N4, Canada. Haocheng.Li@ucalgary.ca.
authors.forename: Haocheng
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Medical Physics, Tom Baker Cancer Centre, 1331 29 Street Northwest, Calgary, AB, T2N 4 N2, Canada. Wendy.Smith@albertahealthservices.ca.|Department of Physics & Astronomy, University of Calgary, 2500 University Dr NW, Calgary, Alberta, T2N 1 N4, Canada. Wendy.Smith@albertahealthservices.ca.|Division of Medical Physics, Department of Oncology, University of Calgary, 2500 University Dr NW, Calgary, Alberta, T2N 1 N4, Canada. Wendy.Smith@albertahealthservices.ca.
authors.forename: Wendy
authors.initials: W
authors.lastname: Smith
authors.affiliation: Department of Medical Physics, Tom Baker Cancer Centre, 1331 29 Street Northwest, Calgary, AB, T2N 4 N2, Canada. Alana.Hudson@albertahealthservices.ca.|Division of Medical Physics, Department of Oncology, University of Calgary, 2500 University Dr NW, Calgary, Alberta, T2N 1 N4, Canada. Alana.Hudson@albertahealthservices.ca.
authors.forename: Alana
authors.initials: A
authors.lastname: Hudson
authors.affiliation: Division of Radiation Oncology, Department of Oncology, University of Calgary,, 2500 University Dr NW, Calgary, Alberta, T2N 1 N4, Canada. Tien.Phan@albertahealthservices.ca.
authors.forename: Tien
authors.initials: T
authors.lastname: Phan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D062485:Breath Holding; D005260:Female; D006321:Heart / Q000528:radiation effects; D006801:Humans; D001239:Inhalation; D008198:Lymph Nodes / Q000528:radiation effects; D008875:Middle Aged; D058958:Organs at Risk; D011832:Radiation Injuries / Q000517:prevention & control*; D011878:Radiotherapy / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D000069584:Unilateral Breast Neoplasms / Q000532:radiotherapy*