title: Radiation pneumonitis: local dose versus [18F]-fluorodeoxyglucose uptake response in irradiated lung.
abstract: OBJECTIVE
  To quantify the relationship between the local radiation dose received and the posttreatment positron emission tomography/computed tomography (PET/CT) [(18)F]2-fluoro-2-deoxyglucose (FDG) uptake in the lung.
  
  
  METHODS
  The data from 36 patients treated for esophageal cancer with thoracic radiotherapy who underwent restaging PET/CT imaging between 4 and 12 weeks after radiotherapy completion were evaluated. Their treatment planning CT was registered with the restaging PET/CT. Using histogram analysis, the voxel average FDG-PET uptake vs. radiation dose was obtained for each case. Hierarchical linear regression models for each patient were applied to study the variation in the linear trends between cases. Deviation of the dose-response curve from a linear model was tested.
  
  
  RESULTS
  The median time between radiotherapy completion and FDG-PET imaging was 40 days (range, 26-70 days). The median of the mean standard uptake value in the lung that received 0-5 Gy was 0.63 (range, 0.36-1.27), 5-10 Gy was 0.77 (range, 0.40-1.35), 10-20 Gy was 0.80 (range, 0.40-1.72), and >20 Gy was 1.08 (range, 0.44-2.63). A hierarchical linear regression model of the radiation dose and normalized FDG uptake per case found an adequate fit with the linear model, and the addition of quadratic and logarithmic functions did not improve the fit. The 36 cases had a posterior mean of slopes range of 0.0048-0.069.
  
  
  CONCLUSIONS
  The regional dose vs. radiation pneumonitis response was evaluated with FDG-PET/CT imaging. Statistical modeling found a linear relationship. The slope of this relationship varied over an order of magnitude, reflecting the range of the underlying biological response to radiation among the study population.
authors.affiliation: Division of Radiation Oncology, University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA. tguerrero@mdanderson.org
authors.forename: Thomas
authors.initials: T
authors.lastname: Guerrero
authors.forename: Valen
authors.initials: V
authors.lastname: Johnson
authors.forename: Justin
authors.initials: J
authors.lastname: Hart
authors.forename: Tinsu
authors.initials: T
authors.lastname: Pan
authors.forename: Meena
authors.initials: M
authors.lastname: Khan
authors.forename: Dershan
authors.initials: D
authors.lastname: Luo
authors.forename: Zhongxing
authors.initials: Z
authors.lastname: Liao
authors.forename: Jaffer
authors.initials: J
authors.lastname: Ajani
authors.forename: Craig
authors.initials: C
authors.lastname: Stevens
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Komaki
mesh_terms: D000328:Adult; D000368:Aged; D004938:Esophageal Neoplasms / Q000532:radiotherapy*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D016014:Linear Models; D008168:Lung / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods; D017564:Radiation Pneumonitis / Q000000981:diagnostic imaging*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D011879:Radiotherapy Dosage; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18