title: Predicting chest wall pain from lung stereotactic body radiotherapy for different fractionation schemes.
abstract: OBJECTIVE
  Recent studies with two fractionation schemes predicted that the volume of chest wall receiving >30 Gy (V30) correlated with chest wall pain after stereotactic body radiation therapy (SBRT) to the lung. This study developed a predictive model of chest wall pain incorporating radiobiologic effects, using clinical data from four distinct SBRT fractionation schemes.
  
  
  METHODS
  102 SBRT patients were treated with four different fractionations: 60 Gy in three fractions, 50 Gy in five fractions, 48 Gy in four fractions, and 50 Gy in 10 fractions. To account for radiobiologic effects, a modified equivalent uniform dose (mEUD) model calculated the dose to the chest wall with volume weighting. For comparison, V30 and maximum point dose were also reported. Using univariable logistic regression, the association of radiation dose and clinical variables with chest wall pain was assessed by uncertainty coefficient (U) and C statistic (C) of receiver operator curve. The significant associations from the univariable model were verified with a multivariable model.
  
  
  RESULTS
  106 lesions in 102 patients with a mean age of 72 were included, with a mean of 25.5 (range, 12-55) months of follow-up. Twenty patients reported chest wall pain at a mean time of 8.1 (95% confidence interval, 6.3-9.8) months after treatment. The mEUD models, V30, and maximum point dose were significant predictors of chest wall pain (p < 0.0005). mEUD improved prediction of chest wall pain compared with V30 (C = 0.79 vs. 0.77 and U = 0.16 vs. 0.11). The mEUD with moderate weighting (a = 5) better predicted chest wall pain than did mEUD without weighting (a = 1) (C = 0.79 vs. 0.77 and U = 0.16 vs. 0.14). Body mass index (BMI) was significantly associated with chest wall pain (p = 0.008). On multivariable analysis, mEUD and BMI remained significant predictors of chest wall pain (p = 0.0003 and 0.03, respectively).
  
  
  CONCLUSIONS
  mEUD with moderate weighting better predicted chest wall pain than did V30, indicating that a small chest wall volume receiving a high radiation dose is responsible for chest wall pain. Independently of dose to the chest wall, BMI also correlated with chest wall pain.
authors.affiliation: Department of Radiation Oncology, Taussig Cancer Center, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: Neil M
authors.initials: NM
authors.lastname: Woody
authors.forename: Gregory M M
authors.initials: GM
authors.lastname: Videtic
authors.forename: Kevin L
authors.initials: KL
authors.lastname: Stephans
authors.forename: Toufik
authors.initials: T
authors.lastname: Djemil
authors.forename: Yongbok
authors.initials: Y
authors.lastname: Kim
authors.forename: Ping
authors.initials: P
authors.lastname: Xia
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000532:radiotherapy*; D002637:Chest Pain / Q000175:diagnosis / Q000209:etiology*; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011832:Radiation Injuries / Q000150:complications*; D011853:Radiobiology; D016634:Radiosurgery / Q000009:adverse effects* / Q000379:methods; D012044:Regression Analysis; D012189:Retrospective Studies; D035441:Thoracic Wall / Q000528:radiation effects*; D013997:Time Factors