title: Time course and predictive factors for lung volume reduction following stereotactic ablative radiotherapy (SABR) of lung tumors.
abstract: BACKGROUND
  Stereotactic ablative volume reduction (SAVR) is a potential alternative to lung-volume reduction surgery in patients with severe emphysema and excessive surgical risk. Having previously observed a dose-volume response for localized lobar volume reduction after stereotactic ablative radiotherapy (SABR) for lung tumors, we investigated the time course and factors associated with volume reduction.
  
  
  METHODS
  We retrospectively identified 70 eligible patients receiving lung tumor SABR during 2007-2013. We correlated lobar volume reduction (relative to total, bilateral lung volume [TLV]) with volume receiving high biologically effective doses (VXXBED3) and other pre-treatment factors in all patients, and measured the time course of volume changes on 3-month interval CT scans in patients with large V60BED3 (n = 21, V60BED3 ≥4.1 % TLV).
  
  
  RESULTS
  Median CT follow-up was 15 months. Median volume reduction of treated lobes was 4.5 % of TLV (range 0.01-13.0 %), or ~9 % of ipsilateral lung volume (ILV); median expansion of non-target adjacent lobes was 2.2 % TLV (-4.6-9.9 %; ~4 % ILV). Treated lobe volume reduction was significantly greater with larger VXXBED3 (XX = 20-100 Gy, R (2) = 0.52-0.55, p < 0.0001) and smaller with lower pre-treatment FEV1% (R (2) = 0.11, p = 0.005) in a multivariable linear model. Maximum volume reduction was reached by ~12 months and persisted.
  
  
  CONCLUSIONS
  We identified a multivariable model for lobar volume reduction after SABR incorporating dose-volume and pre-treatment FEV1% and characterized its time course.
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, 875 Blake Wilbur Drive, Stanford, CA, 94305, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Binkley
authors.affiliation: Stanford Cancer Institute, Stanford University School of Medicine, 875 Blake Wilbur Drive, Stanford, CA, 94305, USA.|Department of Cardiothoracic Surgery, Division of Thoracic Surgery, Stanford University School of Medicine, Stanford, USA.
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Shrager
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, 875 Blake Wilbur Drive, Stanford, CA, 94305, USA.
authors.forename: Aadel
authors.initials: A
authors.lastname: Chaudhuri
authors.affiliation: Department of Health Research & Policy, Stanford University School of Medicine, Stanford, USA.
authors.forename: Rita
authors.initials: R
authors.lastname: Popat
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, 875 Blake Wilbur Drive, Stanford, CA, 94305, USA.|Stanford Cancer Institute, Stanford University School of Medicine, 875 Blake Wilbur Drive, Stanford, CA, 94305, USA.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Maxim
authors.affiliation: Princess Margaret Cancer Centre, Toronto, Ontario, Canada.|University of Toronto, Toronto, Canada.
authors.forename: David Benjamin
authors.initials: DB
authors.lastname: Shultz
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, 875 Blake Wilbur Drive, Stanford, CA, 94305, USA. Diehn@Stanford.edu.|Stanford Cancer Institute, Stanford University School of Medicine, 875 Blake Wilbur Drive, Stanford, CA, 94305, USA. Diehn@Stanford.edu.|Institute for Stem Cell Biology & Regenerative Medicine, Stanford University School of Medicine, 875 Blake Wilbur Drive, Stanford, CA, 94305, USA. Diehn@Stanford.edu.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Diehn
authors.affiliation: Department of Radiation Oncology, Stanford University School of Medicine, 875 Blake Wilbur Drive, Stanford, CA, 94305, USA. BWLoo@stanford.edu.|Stanford Cancer Institute, Stanford University School of Medicine, 875 Blake Wilbur Drive, Stanford, CA, 94305, USA. BWLoo@stanford.edu.
authors.forename: Billy W
authors.initials: BW
authors.lastname: Loo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D004646:Emphysema / Q000150:complications / Q000532:radiotherapy; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D016014:Linear Models; D008168:Lung / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011013:Pneumonectomy; D049268:Positron-Emission Tomography; D016634:Radiosurgery; D011878:Radiotherapy / Q000379:methods*; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
chemical_list: D019788:Fluorodeoxyglucose F18
keywords: Emphysema; Stereotactic ablative radiotherapy