title: Framework for radiation pneumonitis risk stratification based on anatomic and perfused lung dosimetry.
abstract: OBJECTIVE
  To design and apply a framework for predicting symptomatic radiation pneumonitis in patients undergoing thoracic radiation, using both pretreatment anatomic and perfused lung dose-volume parameters.
  
  
  METHODS
  Radiation treatment planning CT scans were coregistered with pretreatment [99mTc]MAA perfusion SPECT/CT scans of 20 patients who underwent definitive thoracic radiation. Clinical radiation pneumonitis was defined as grade ≥ 2 (CTCAE v4 grading system). Anatomic lung dose-volume parameters were collected from the treatment planning scans. Perfusion dose-volume parameters were calculated from pretreatment SPECT/CT scans. Equivalent doses in 2 Gy per fraction were calculated in the lung to account for differences in treatment regimens and spatial variations in lung dose (EQD2lung).
  
  
  RESULTS
  Anatomic lung dosimetric parameters (MLD) and functional lung dosimetric parameters (pMLD70%) were identified as candidate predictors of grade ≥ 2 radiation pneumonitis (AUC > 0.93, p < 0.01). Pairing of an anatomic and functional dosimetric parameter (e. g., MLD and pMLD70%) may further improve prediction accuracy. Not all individuals with high anatomic lung dose (MLD > 13.6 GyEQD2lung, 19.3 Gy for patients receiving 60 Gy in 30 fractions) developed radiation pneumonitis, but all individuals who also had high mean dose to perfused lung (pMLD70%> 13.3 GyEQD2) developed radiation pneumonitis.
  
  
  CONCLUSIONS
  The preliminary application of this framework revealed differences between anatomic and perfused lung dosimetry in this limited patient cohort. The addition of perfused lung parameters may help risk stratify patients for radiation pneumonitis, especially in treatment plans with high anatomic mean lung dose. Further investigations are warranted.
authors.affiliation: Department of Radiation Oncology, University of Washington School of Medicine, 98195, Seattle, WA, USA.
authors.forename: Gurleen
authors.initials: G
authors.lastname: Dhami
authors.affiliation: Department of Radiation Oncology, University of Washington School of Medicine, 98195, Seattle, WA, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Zeng
authors.affiliation: Department of Radiology, University of Washington School of Medicine, 98195, Seattle, WA, USA.
authors.forename: Hubert J
authors.initials: HJ
authors.lastname: Vesselle
authors.affiliation: Department of Radiology, University of Washington School of Medicine, 98195, Seattle, WA, USA.
authors.forename: Paul E
authors.initials: PE
authors.lastname: Kinahan
authors.affiliation: Department of Radiology, University of Washington School of Medicine, 98195, Seattle, WA, USA.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Miyaoka
authors.affiliation: Department of Radiation Oncology, University of Washington School of Medicine, 98195, Seattle, WA, USA.
authors.forename: Shilpen A
authors.initials: SA
authors.lastname: Patel
authors.affiliation: Department of Radiation Oncology, University of Washington School of Medicine, 98195, Seattle, WA, USA.
authors.forename: Ramesh
authors.initials: R
authors.lastname: Rengan
authors.affiliation: Department of Radiation Oncology, University of Washington School of Medicine, 98195, Seattle, WA, USA. srbowen@uw.edu.|Department of Radiology, University of Washington School of Medicine, 98195, Seattle, WA, USA. srbowen@uw.edu.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Bowen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D017564:Radiation Pneumonitis / Q000175:diagnosis* / Q000209:etiology* / Q000517:prevention & control; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods; D012680:Sensitivity and Specificity; D000072098:Single Photon Emission Computed Tomography Computed Tomography / Q000379:methods; D016896:Treatment Outcome
keywords: Computed tomography; Radiotherapy; SPECT; Sequelae; Toxicity