title: Treatment planning study of Volumetric Modulated Arc Therapy and three dimensional field-in-field techniques for left chest-wall cancers with regional lymph nodes.
abstract: OBJECTIVE
  This study aims to investigate whether there are dosimetric advantages to using VMAT (Volumetric Modulated Arc Therapy) for left-sided chest-wall patients over the three-dimensional conformal field-in-field (FinF) technique.
  
  
  BACKGROUND
  There is a lack of dosimetric studies dedicated for chest-wall patients. Potential dosimetric advantage could be obtained using VMAT due to complex geometry of PTVs (Planning Target Volumes) and OARs (Organs at Risk) in chest-wall and lymph nodes.
  
  
  METHODS
  VMAT and FinF plans were generated and evaluated based on DVHs (Dose Volume Histograms) for both PTVs and OARs for 22 left-sided chest-wall patients with involved regional nodes. PTV HIs (Homogeneity Indices) and CIs (Conformity Indices), and EUDs (Equivalent Uniform Doses) for PTVs and OARs were also evaluated for comparisons between VMAT and FinF.
  
  
  RESULTS
  FinF planning met PTV criteria adequately in all cases except two. In these two cases, VMAT was able to meet PTV criteria adequately. VMAT demonstrated significant reduction in left lung V20 Gyin chest-wall patients compared to FinF plans. The volumes of the right lung and right breast receiving 5 Gy were much higher in VMAT than those in FinF for all patients.
  
  
  CONCLUSIONS
  Compared to the FinF technique, there is a generally limited benefit using VMAT for left-sided chest-wall patients due to large low-dose-bath to OARs with insignificant improvement in PTV coverage. In case where FinF planning cannot meet dose constrains, VMAT provides a viable option. The use of VMAT planning over the FinF technique in chest-wall cancers should be carefully analyzed on an individual basis.
authors.affiliation: Cape Breton Cancer Centre, Nova Scotia Health Authority, 1482 George St., Sydney, NS, Canada B1P 1P3; Department of Radiation Oncology, Dalhousie University, Halifax, NS, Canada.
authors.forename: Heping
authors.initials: H
authors.lastname: Xu
authors.affiliation: Cape Breton Cancer Centre, Nova Scotia Health Authority, 1482 George St., Sydney, NS, Canada B1P 1P3.
authors.forename: Gillian
authors.initials: G
authors.lastname: Hatcher
keywords: 3D CRT; Breast cancer; Chest-wall cancer; Radiotherapy; VMAT