title: Intensity-modulated proton therapy for elective nodal irradiation and involved-field radiation in the definitive treatment of locally advanced non-small-cell lung cancer: a dosimetric study.
abstract: BACKGROUND
  Photon involved-field (IF) radiation therapy (IFRT), the standard for locally advanced (LA) non-small cell lung cancer (NSCLC), results in favorable outcomes without increased isolated nodal failures, perhaps from scattered dose to elective nodal stations. Because of the high conformality of intensity-modulated proton therapy (IMPT), proton IFRT could increase nodal failures. We investigated the feasibility of IMPT for elective nodal irradiation (ENI) in LA-NSCLC.
  
  
  METHODS
  IMPT IFRT plans were generated to the same total dose of 66.6-72 Gy received by 20 LA-NSCLC patients treated with photon IFRT. IMPT ENI plans were generated to 46 cobalt Gray equivalent (CGE) to elective nodal planning treatment volumes (PTV) plus 24 CGE to IF-PTVs.
  
  
  RESULTS
  Proton IFRT and ENI improved the IF-PTV percentage of volume receiving 95% of the prescribed dose (D95) by 4% (P < .01) compared with photon IFRT. All evaluated dosimetric parameters improved significantly with both proton plans. The lung percentage of volume receiving 20 Gy/CGE (V20) and mean lung dose decreased 18% (P < .01) and 36% (P < .01), respectively, with proton IFRT, and 11% (P = .03) and 26% (P < .01) with ENI. The mean esophagus dose decreased 16% with IFRT and 12% with ENI; heart V25 decreased 63% with both (all P < .01).
  
  
  CONCLUSIONS
  This study demonstrates the feasibility of IMPT for LA-NSCLC ENI. Potential decreased toxicity indicates that IMPT could allow ENI while maintaining a favorable therapeutic ratio compared with photon IFRT.
authors.affiliation: Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD. Electronic address: aparna.kesarwala@nih.gov.
authors.forename: Aparna H
authors.initials: AH
authors.lastname: Kesarwala
authors.affiliation: Division of Radiation Oncology, Department of Radiology, Walter Reed National Military Medical Center, Bethesda, MD.
authors.forename: Christine J
authors.initials: CJ
authors.lastname: Ko
authors.affiliation: Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Holly
authors.initials: H
authors.lastname: Ning
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA.
authors.forename: Eric
authors.initials: E
authors.lastname: Xanthopoulos
authors.affiliation: Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Karl E
authors.initials: KE
authors.lastname: Haglund
authors.affiliation: Division of Radiation Oncology, Department of Radiology, Walter Reed National Military Medical Center, Bethesda, MD.
authors.forename: William P
authors.initials: WP
authors.lastname: O'Meara
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA.
authors.forename: Charles B
authors.initials: CB
authors.lastname: Simone
authors.affiliation: Department of Radiation Oncology, University of Washington, Seattle, WA.
authors.forename: Ramesh
authors.initials: R
authors.lastname: Rengan
mesh_terms: D000368:Aged; D002289:Carcinoma, Non-Small-Cell Lung / Q000532:radiotherapy*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D008198:Lymph Nodes / Q000528:radiation effects; D008297:Male; D008875:Middle Aged; D061766:Proton Therapy / Q000009:adverse effects / Q000379:methods*; D011874:Radiometry; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000009:adverse effects / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D047368:Tumor Burden
keywords: ENI; IFRT; IMPT; NSCLC; Radiation therapy