title: Dose-Volume Predictors of Esophagitis After Thoracic Stereotactic Body Radiation Therapy.
abstract: OBJECTIVE
  Esophageal toxicity has become a major concern as stereotactic hypofractionated radiation therapy is increasingly utilized for central pulmonary tumors. Our purpose was to define esophageal dosimetric parameters that predict potentially dose-limiting toxicities.
  
  
  METHODS
  In total, 157 patients with a planning target volume ≤5 cm from the esophagus were selected from an institutional database. Toxicity was scored with the CTCAE v4.0. Esophageal Dmax and Dv (dose D in Gy covering volume v in mL) in 0.5 mL increments were collected. Corresponding biologically effective dose (BED) was calculated for α/β=10,3 (BED10, BED3). Normal tissue complication probability was computed with conventionally fractionated radiotherapy parameters and equivalent dose in 2 Gy per fraction (EQD2). Dosimetric predictors were identified with multivariate logistic regression with a manual forward stepwise selection technique.
  
  
  RESULTS
  The grade≥2 esophagitis rate was 5.7%. BED10 to 1.5 mL was the best predictor of esophagitis. BED10 to 0.5, 1.0, 2.0, 3.0, and 3.5 mL were also predictive but less strong. Results were similar when BED3 and physical dose were examined. Tumor-esophageal distance correlated with esophagitis (10.5% risk of≥grade 2 events with distance≤3.9 cm vs. 1.3% when>3.9 cm, P=0.016). BED10 to 1.5 mL correlated well with EQD2 normal tissue complication probability estimates.
  
  
  CONCLUSIONS
  BED to 1.5 mL was the strongest predictor of grade≥2 esophagitis (independent of α/β ratio) with a 10.6% toxicity risk when BED10>21.1 Gy (14.3 Gy in 3 fractions, 16.0 Gy in 5). The overall rate of severe toxicity is low, suggesting that higher doses may be tolerable.
authors.affiliation: Department of Therapeutic Radiology, Yale University School of Medicine, Yale Cancer Center, New Haven, CT.
authors.forename: Eileen M
authors.initials: EM
authors.lastname: Harder
authors.forename: Zhe Jay
authors.initials: ZJ
authors.lastname: Chen
authors.forename: Henry S
authors.initials: HS
authors.lastname: Park
authors.forename: Brandon R
authors.initials: BR
authors.lastname: Mancini
authors.forename: Roy H
authors.initials: RH
authors.lastname: Decker
mesh_terms: D000368:Aged; D004307:Dose-Response Relationship, Radiation; D004941:Esophagitis / Q000209:etiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D011832:Radiation Injuries / Q000209:etiology*; D016634:Radiosurgery / Q000009:adverse effects* / Q000379:methods; D011879:Radiotherapy Dosage