title: Comparison of intensity-modulated radiotherapy, adaptive radiotherapy, proton radiotherapy, and adaptive proton radiotherapy for treatment of locally advanced head and neck cancer.
abstract: OBJECTIVE
  Various radiotherapy planning methods for locally advanced squamous cell carcinoma of the head and neck (SCCHN) have been proposed to decrease normal tissue toxicity. We compare IMRT, adaptive IMRT, proton therapy (IMPT), and adaptive IMPT for SCCHN.
  
  
  METHODS
  Initial and re-simulation CT images from 10 consecutive patients with SCCHN were used to quantify dosimetric differences between photon and proton therapy. Contouring was performed on both CTs, and plans (n=40 plans) and dose-volume histograms were generated.
  
  
  RESULTS
  The mean GTV volume decreased 53.4% with re-simulation. All plans provided comparable PTV coverage. Compared with IMRT, adaptive IMRT significantly reduced the maximum dose to the mandible (p=0.020) and mean doses to the contralateral parotid gland (p=0.049) and larynx (p=0.049). Compared with IMRT and adaptive IMRT, IMPT significantly lowered the maximum doses to the spinal cord (p<0.002 for both) and brainstem (p<0.002 for both) and mean doses to the larynx (p<0.002 for both) and ipsilateral (p=0.004 IMRT, p=0.050 adaptive) and contralateral (p<0.002 IMRT, p=0.010 adaptive) parotid glands. Adaptive IMPT significantly reduced doses to all critical structures compared with IMRT and adaptive IMRT and several critical structures compared with non-adaptive IMPT.
  
  
  CONCLUSIONS
  Although adaptive IMRT reduced dose to several normal structures compared with standard IMRT, non-adaptive proton therapy had a more favorable dosimetric profile than IMRT or adaptive IMRT and may obviate the need for adaptive planning. Protons allowed significant sparing of the spinal cord, parotid glands, larynx, and brainstem and should be considered for SCCHN to decrease normal tissue toxicity while still providing optimal tumor coverage.
authors.affiliation: National Institutes of Health, National Cancer Institute, Radiation Oncology Branch, Bethesda 20982, USA. simonen@mail.nih.gov
authors.forename: Charles B
authors.initials: CB
authors.lastname: Simone
authors.forename: David
authors.initials: D
authors.lastname: Ly
authors.forename: Tu D
authors.initials: TD
authors.lastname: Dan
authors.forename: John
authors.initials: J
authors.lastname: Ondos
authors.forename: Holly
authors.initials: H
authors.lastname: Ning
authors.forename: Arnaud
authors.initials: A
authors.lastname: Belard
authors.forename: John
authors.initials: J
authors.lastname: O'Connell
authors.forename: Robert W
authors.initials: RW
authors.lastname: Miller
authors.forename: Nicole L
authors.initials: NL
authors.lastname: Simone
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy*; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D061766:Proton Therapy; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D000077195:Squamous Cell Carcinoma of Head and Neck