title: Hybrid IMRT for treatment of cancers of the lung and esophagus.
abstract: OBJECTIVE
  To report on a hybrid intensity-modulated radiation therapy (IMRT; static plus IMRT beams treated concurrently) technique for lung and esophageal patients to reduce the volume of lung treated to low doses while delivering a conformal dose distribution.
  
  
  METHODS
  Treatment plans were analyzed for 18 patients (12 lung and 6 esophageal). Patients were treated with a hybrid technique that concurrently combines static (approximately two-thirds dose) and IMRT (approximately one-third dose) beams. These plans were compared with conventional three-dimensional (3D; non-IMRT) plans and all IMRT plans using custom four- and five-field arrangements and nine equally spaced coplanar beams. Plans were optimized to reduce V13 and V5 values. Dose-volume histograms were calculated for the planning target volume, heart, and the ipsilateral, contralateral, and total lung. Lung volumes V5, V13, V20, V30; mean lung dose (MLD); and the generalized equivalent uniform dose (gEUD) were calculated for each plan.
  
  
  RESULTS
  Hybrid plans treated significantly smaller total and contralateral lung volumes with low doses than nine-field IMRT plans. Largest reductions were for contralateral lung V5, V13, and V20 values for lung (-11%, -15%, -7%) and esophageal (-16%, -20%, -7%) patients. Smaller reductions were found also for 3D and four- and five-field IMRT plans. MLD and gEUDs were similar for all plan types. The 3D plans treated much larger extra planning target volumes to prescribed dose levels.
  
  
  CONCLUSIONS
  Hybrid IMRT demonstrated advantages for reduction of low-dose lung volumes in the thorax for reducing low dose to lung while also reducing the potential magnitude of dose deviations due to intrafraction motion and small field calculation accuracy.
authors.affiliation: University of Massachusetts Medical School, Department of Radiation Oncology, 55 Lake Avenue North, Worcester, MA 01655, USA. mayoc@ummhc.org
authors.forename: Charles S
authors.initials: CS
authors.lastname: Mayo
authors.forename: Marcia M
authors.initials: MM
authors.lastname: Urie
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Fitzgerald
authors.forename: Linda
authors.initials: L
authors.lastname: Ding
authors.forename: Yuan Chyuan
authors.initials: YC
authors.lastname: Lo
authors.forename: Madeleine
authors.initials: M
authors.lastname: Bogdanov
mesh_terms: D004938:Esophageal Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D047368:Tumor Burden