title: Dosimetric predictors of radiation-induced acute nausea and vomiting in IMRT for nasopharyngeal cancer.
abstract: OBJECTIVE
  We wanted to investigate dosimetric parameters that would predict radiation-induced acute nausea and vomiting in intensity-modulated radiation therapy (IMRT) for undifferentiated carcinoma of the nasopharynx (NPC).
  
  
  METHODS
  Forty-nine consecutive patients with newly diagnosed NPC were treated with IMRT alone in this prospective study. Patients receiving any form of chemotherapy were excluded. The dorsal vagal complex (DVC) as well as the left and right vestibules (VB-L and VB-R, respectively) were contoured on planning computed tomography images. A structure combining both the VB-L and the VB-R, named VB-T, was also generated. All structures were labeled organs at risk (OAR). A 3-mm three-dimensional margin was added to these structures and labeled DVC+3 mm, VB-L+3 mm, VB-R+3 mm, and VB-T+3 mm to account for physiological body motion and setup error. No weightings were given to these structures during optimization in treatment planning. Dosimetric parameters were recorded from dose-volume histograms. Statistical analysis of parameters' association with nausea and vomiting was performed using univariate and multivariate logistic regression.
  
  
  RESULTS
  Six patients (12.2%) reported Grade 1 nausea, and 8 patients (16.3%) reported Grade 2 nausea. Also, 4 patients (8.2%) complained of Grade 1 vomiting, and 4 patients (8.2%) experienced Grade 2 vomiting. No patients developed protracted nausea and vomiting after completion of IMRT. For radiation-induced acute nausea, V40 (percentage volume receiving at least 40Gy) to the VB-T and V40>=80% to the VB-T were predictors, using univariate analysis. On multivariate analysis, V40>=80% to the VB-T was the only predictor. There were no predictors of radiation-induced acute vomiting, as the number of events was too small for analysis.
  
  
  CONCLUSIONS
  This is the first study demonstrating that a V40 to the VB-T is predictive of radiation-induced acute nausea. The vestibules should be labeled as sensitive OARs, and weightings should be considered for dose sparing during optimization in the treatment planning of IMRT.
authors.affiliation: Department of Clinical Oncology, The University of Hong Kong, Queen Mary Hospital, Hong Kong. vhflee@hku.hk
authors.forename: Victor H F
authors.initials: VH
authors.lastname: Lee
authors.forename: Sherry C Y
authors.initials: SC
authors.lastname: Ng
authors.forename: T W
authors.initials: TW
authors.lastname: Leung
authors.forename: Gordon K H
authors.initials: GK
authors.lastname: Au
authors.forename: Dora L W
authors.initials: DL
authors.lastname: Kwong
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000000981:diagnostic imaging; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement; D009303:Nasopharyngeal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D009325:Nausea / Q000145:classification / Q000209:etiology*; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects*; D011446:Prospective Studies; D011859:Radiography; D011880:Radiotherapy Planning, Computer-Assisted; D061106:Radiotherapy Setup Errors; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects*; D012043:Regression, Psychology; D047368:Tumor Burden; D014630:Vagus Nerve / Q000000981:diagnostic imaging / Q000528:radiation effects*; D014722:Vestibule, Labyrinth / Q000000981:diagnostic imaging / Q000528:radiation effects*; D014839:Vomiting / Q000145:classification / Q000209:etiology*