title: Pulmonary dose-volume predictors of radiation pneumonitis following stereotactic body radiation therapy.
abstract: OBJECTIVE
  Radiation pneumonitis (RP) may be severe after stereotactic body radiation therapy. Our purpose was to identify pulmonary and cardiac dosimetric parameters that predicted for post-stereotactic body radiation therapy grade ≥2 RP.
  
  
  METHODS
  A total of 335 patients with ≥3 months' follow-up were included. Normal pulmonary volume was total lungs minus gross tumor volume. Pulmonary maximum dose, mean lung dose (MLD), and the percent of lung receiving ≥x Gy for 5 to 50 Gy in 5-Gy increments were collected. Cardiac maximum dose, mean dose, volume of lung receiving ≥0.1 Gy (V0.1), V0.25 to V1, and V2.5 to V12.5 were recorded. Multivariable logistic regression with manual backward stepwise elimination was used to identify the best dosimetric predictors of toxicity. Optimal dose-volume cutoffs were isolated with recursive partitioning analysis (RPA).
  
  
  RESULTS
  The grade ≥2 RP rate was 18.8%. Pulmonary V5 to V50, MLD, and cardiac V0.1 to V2.5 were significantly associated with toxicity on univariate analysis. On multivariable logistic regression, V10 was the strongest dosimetric predictor of grade ≥2 RP (odds ratio, 1.052; 95% confidence interval, 1.014-1.092; P = .007). RPA identified a 21.6% risk of grade ≥2 RP with V10 ≥6.14% (vs 3.8% with <6.14). MLD was the most significant predictor of grade ≥3 RP (odds ratio, 1.002; 95% confidence interval, 1.000-1.003; P = .031). RPA identified a 25.0% risk of grade ≥3 RP with MLD ≥7.84 Gy (vs 8.0% when <7.84 Gy).
  
  
  CONCLUSIONS
  With a grade ≥2 RP rate of 18.8%, lung V10 was the best predictor of grade ≥2 toxicity. MLD was the best predictor of grade ≥3 RP.
authors.affiliation: Department of Therapeutic Radiology, Yale University School of Medicine, Yale Cancer Center, New Haven, Connecticut. Electronic address: eileen.harder@yale.edu.
authors.forename: Eileen M
authors.initials: EM
authors.lastname: Harder
authors.affiliation: Department of Therapeutic Radiology, Yale University School of Medicine, Yale Cancer Center, New Haven, Connecticut.
authors.forename: Henry S
authors.initials: HS
authors.lastname: Park
authors.affiliation: Department of Therapeutic Radiology, Yale University School of Medicine, Yale Cancer Center, New Haven, Connecticut.
authors.forename: Zhe Jay
authors.initials: ZJ
authors.lastname: Chen
authors.affiliation: Department of Therapeutic Radiology, Yale University School of Medicine, Yale Cancer Center, New Haven, Connecticut.
authors.forename: Roy H
authors.initials: RH
authors.lastname: Decker
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D016015:Logistic Models; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D008176:Lung Volume Measurements; D008297:Male; D015999:Multivariate Analysis; D016017:Odds Ratio; D017564:Radiation Pneumonitis / Q000453:epidemiology* / Q000209:etiology; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D012307:Risk Factors; D047368:Tumor Burden