title: Analysis of the impact of chest wall constraints on eligibility for a randomized trial of stereotactic body radiotherapy of peripheral stage I non-small cell lung cancer.
abstract: BACKGROUND
  Chest wall toxicities are recognized complications of stereotactic radiotherapy (SBRT) in non-small cell lung cancer. To minimize toxicity, the Trans-Tasman Radiation Oncology Group (TROG) 09.02 'CHISEL' study protocol excluded patients with tumours within 1 cm of the chest wall. The purpose of this study is to evaluate the implication of chest wall proximity constraints on patient eligibility, toxicity and potential accrual.
  
  
  METHODS
  Exclusion zones of 1 cm beyond the mediastinum and 2 cm beyond the bifurcation of the lobar bronchi were incorporated into the CHISEL credentialing CT dataset. Volumes of lung within which tumours varying from 1 cm to 5 cm in diameter may occupy and remain eligible for the CHISEL study were calculated. These volumes were compared to a hypothetical model in which the 1 cm chest wall proximity restriction was removed.
  
  
  RESULTS
  The percentage of lung area in which a tumour mass can occupy and be suitable for CHISEL in the left and right lung were 54% and 60% respectively. Removing the constraint increased the percentage of available lung to 83% and 87% respectively. Considering a 2 cm spherical tumour, only 21% and 31% of tumours in the left and right lung would be eligible with the chest wall constraint, whilst 39% and 50% respectively would be eligible without the constraint.
  
  
  CONCLUSIONS
  The exclusion of tumours less than 1 cm to chest wall significantly reduces the proportion of patients eligible for the CHISEL protocol. A review of the literature pertaining to chest wall toxicity after stereotactic radiotherapy supports a change in chest wall exclusion criteria for the CHISEL study.
authors.affiliation: Department of Radiation Oncology, University of Melbourne, Melbourne, Victoria, Australia. shankar.siva@petermac.org
authors.forename: Shankar
authors.initials: S
authors.lastname: Siva
authors.forename: Mark
authors.initials: M
authors.lastname: Shaw
authors.forename: Brent
authors.initials: B
authors.lastname: Chesson
authors.forename: Suki
authors.initials: S
authors.lastname: Gill
authors.forename: David
authors.initials: D
authors.lastname: Ball
mesh_terms: D059925:Anatomic Landmarks / Q000000981:diagnostic imaging; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000601:surgery*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery*; D008297:Male; D018579:Patient Selection; D011379:Prognosis; D016634:Radiosurgery / Q000379:methods*; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods; D035441:Thoracic Wall / Q000000981:diagnostic imaging* / Q000601:surgery; D014057:Tomography, X-Ray Computed / Q000379:methods