title: Reduced lung dose during radiotherapy for thoracic esophageal carcinoma: VMAT combined with active breathing control for moderate DIBH.
abstract: BACKGROUND
  Lung radiation injury is a critical complication of radiotherapy (RT) for thoracic esophageal carcinoma (EC). Therefore, the goal of this study was to investigate the feasibility and dosimetric effects of reducing the lung tissue irradiation dose during RT for thoracic EC by applying volumetric modulated arc radiotherapy (VMAT) combined with active breathing control (ABC) for moderate deep inspiration breath-hold (mDIBH).
  
  
  METHODS
  Fifteen patients with thoracic EC were randomly selected to undergo two series of computed tomography (CT) simulation scans with ABC used to achieve mDIBH (representing 80% of peak DIBH value) versus free breathing (FB). Gross tumor volumes were contoured on different CT images, and planning target volumes (PTVs) were obtained using different margins. For PTV-FB, intensity-modulated radiotherapy (IMRT) was designed with seven fields, and VMAT included two whole arcs. For PTV-DIBH, VMAT with three 135° arcs was applied, and the corresponding plans were named: IMRT-FB, VMAT-FB, and VMAT-DIBH, respectively. Dosimetric differences between the different plans were compared.
  
  
  RESULTS
  The heart volumes decreased by 19.85%, while total lung volume increased by 52.54% in mDIBH, compared to FB (p < 0.05). The mean conformality index values and homogeneity index values for VMAT-DIBH (0.86, 1.07) were slightly worse than those for IMRT-FB (0.90, 1.05) and VMAT-FB (0.90, 1.06) (p > 0.05). Furthermore, compared to IMRT-FB and VMAT-FB, VMAT-DIBH reduced the mean total lung dose by 18.64% and 17.84%, respectively (p < 0.05); moreover, the V5, V10, V20, and V30 values for IMRT-FB and VMAT-FB were reduced by 10.84% and 10.65% (p > 0.05), 12.5% and 20% (p < 0.05), 30.77% and 33.33% (p < 0.05), and 50.33% and 49.15% (p < 0.05), respectively. However, the heart dose-volume indices were similar between VMAT-DIBH and VMAT-FB which were lower than IMRT-FB without being statistically significant (p > 0.05). The monitor units and treatment time of VMAT-DIBH were also the lowest (p < 0.05).
  
  
  CONCLUSIONS
  VMAT combined with ABC to achieve mDIBH is a feasible approach for RT of thoracic EC. Furthermore, this method has the potential to effectively reduce lung dose in a shorter treatment time and with better targeting accuracy.
authors.forename: Guanzhong
authors.initials: G
authors.lastname: Gong
authors.forename: Ruozheng
authors.initials: R
authors.lastname: Wang
authors.forename: Yujie
authors.initials: Y
authors.lastname: Guo
authors.forename: Deyin
authors.initials: D
authors.lastname: Zhai
authors.forename: Tonghai
authors.initials: T
authors.lastname: Liu
authors.forename: Jie
authors.initials: J
authors.lastname: Lu
authors.forename: Jinhu
authors.initials: J
authors.lastname: Chen
authors.forename: Chengxin
authors.initials: C
authors.lastname: Liu
authors.affiliation: Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Jinan 250117, China. yongyinsd@163.com.
authors.forename: Yong
authors.initials: Y
authors.lastname: Yin
mesh_terms: D000328:Adult; D000368:Aged; D004938:Esophageal Neoplasms / Q000532:radiotherapy*; D005260:Female; D006321:Heart / Q000502:physiology; D006801:Humans; D008168:Lung / Q000502:physiology / Q000528:radiation effects*; D008297:Male; D008875:Middle Aged; D009068:Movement; D058958:Organs at Risk; D011874:Radiometry / Q000379:methods; D011878:Radiotherapy / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D011897:Random Allocation; D015203:Reproducibility of Results; D012119:Respiration; D013899:Thoracic Neoplasms / Q000532:radiotherapy*; D014057:Tomography, X-Ray Computed