title: Intensity-modulated proton therapy further reduces normal tissue exposure during definitive therapy for locally advanced distal esophageal tumors: a dosimetric study.
abstract: OBJECTIVE
  We have previously found that ≤ 75% of treatment failures after chemoradiotherapy for unresectable esophageal cancer appear within the gross tumor volume and that intensity-modulated (photon) radiotherapy (IMRT) might allow dose escalation to the tumor without increasing normal tissue toxicity. Proton therapy might allow additional dose escalation, with even lower normal tissue toxicity. In the present study, we compared the dosimetric parameters for photon IMRT with that for intensity-modulated proton therapy (IMPT) for unresectable, locally advanced, distal esophageal cancer.
  
  
  METHODS
  Four plans were created for each of 10 patients. IMPT was delivered using anteroposterior (AP)/posteroanterior beams, left posterior oblique/right posterior oblique (LPO/RPO) beams, or AP/LPO/RPO beams. IMRT was delivered with a concomitant boost to the gross tumor volume. The dose was 65.8 Gy to the gross tumor volume and 50.4 Gy to the planning target volume in 28 fractions.
  
  
  RESULTS
  Relative to IMRT, the IMPT (AP/posteroanterior) plan led to considerable reductions in the mean lung dose (3.18 vs. 8.27 Gy, p<.0001) and the percentage of lung volume receiving 5, 10, and 20 Gy (p≤.0006) but did not reduce the cardiac dose. The IMPT LPO/RPO plan also reduced the mean lung dose (4.9 Gy vs. 8.2 Gy, p<.001), the heart dose (mean cardiac dose and percentage of the cardiac volume receiving 10, 20, and 30 Gy, p≤.02), and the liver dose (mean hepatic dose 5 Gy vs. 14.9 Gy, p<.0001). The IMPT AP/LPO/RPO plan led to considerable reductions in the dose to the lung (p≤.005), heart (p≤.003), and liver (p≤.04).
  
  
  CONCLUSIONS
  Compared with IMRT, IMPT for distal esophageal cancer lowered the dose to the heart, lung, and liver. The AP/LPO/RPO beam arrangement was optimal for sparing all three organs. The dosimetric benefits of protons will need to be tailored to each patient according to their specific cardiac and pulmonary risks. IMPT for esophageal cancer will soon be investigated further in a prospective trial at our institution.
authors.affiliation: Department of Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA. jwelsh@mdanderson.org
authors.forename: James
authors.initials: J
authors.lastname: Welsh
authors.forename: Daniel
authors.initials: D
authors.lastname: Gomez
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Palmer
authors.forename: Beverly A
authors.initials: BA
authors.lastname: Riley
authors.forename: Amin V
authors.initials: AV
authors.lastname: Mayankkumar
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Komaki
authors.forename: Lei
authors.initials: L
authors.lastname: Dong
authors.forename: X Ronald
authors.initials: XR
authors.lastname: Zhu
authors.forename: Anna
authors.initials: A
authors.lastname: Likhacheva
authors.forename: Zhongxing
authors.initials: Z
authors.lastname: Liao
authors.forename: Wayne L
authors.initials: WL
authors.lastname: Hofstetter
authors.forename: Jaffer A
authors.initials: JA
authors.lastname: Ajani
authors.forename: James D
authors.initials: JD
authors.lastname: Cox
mesh_terms: D004938:Esophageal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D006321:Heart / Q000000981:diagnostic imaging / Q000528:radiation effects; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging / Q000528:radiation effects; D008168:Lung / Q000000981:diagnostic imaging / Q000528:radiation effects; D058958:Organs at Risk / Q000528:radiation effects*; D017785:Photons / Q000627:therapeutic use; D061766:Proton Therapy; D011832:Radiation Injuries / Q000517:prevention & control*; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D047368:Tumor Burden; D011522:Protons
chemical_list: D011522:Protons