title: Predictive parameters of symptomatic radiation pneumonitis following stereotactic or hypofractionated radiotherapy delivered using volumetric modulated arcs.
abstract: OBJECTIVE
  To identify dosimetric factors that predict development of radiation pneumonitis (RP) following stereotactic or hypofractionated radiotherapy for lung tumors.
  
  
  METHODS
  Seventy-nine consecutive patients with either a planning target volume (PTV)>100 cm(3) (n=69) or prior pneumonectomy or bi-lobectomy (n=13) were identified. Radiation doses (range: 5-50 Gy, with 5 Gy increments) were converted to equivalent doses (EQD(2 Gy)) (α/β=3). Total lung (TL), ipsilateral (IL) and contralateral lung (CL) volumes minus PTV, receiving 5 Gy (V5) up to 50 Gy (V50) and mean lung dose (MLD) were analyzed. Predictors of grade ≥3 RP (CTCAEv4.03) were identified with concordance-statistics (C-statistic) and p-values used to quantify the performance of the model. Factors found to be significant were entered into a recursive partitioning analysis (RPA).
  
  
  RESULTS
  Median PTV was 150 cm(3). Grade ≥3 RP was observed in 8 patients (10%). In univariable analysis, CL-MLD, CL-V5-15, TL-MLD, TL-V5-V10 and ITV size were predictive of RP (p<0.05). In multivariable analysis, contralateral MLD (p=.007) and ITV (p=.063) were the strongest predictors of grade ≥3 RP, with excellent discrimination (C-statistic: 0.868).
  
  
  CONCLUSIONS
  Contralateral MLD and ITV size are both strong predictors of grade ≥3 RP post treatment. Planning constraints should aim to keep contralateral MLD below 3.6 Gy.
authors.affiliation: Department of Radiation Oncology, VU University Medical Center, Amsterdam, The Netherlands. Electronic address: e.bongers@vumc.nl.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Bongers
authors.forename: Angela
authors.initials: A
authors.lastname: Botticella
authors.forename: David A
authors.initials: DA
authors.lastname: Palma
authors.forename: Cornelis J A
authors.initials: CJ
authors.lastname: Haasbeek
authors.forename: Andrew
authors.initials: A
authors.lastname: Warner
authors.forename: Wilko F A R
authors.initials: WF
authors.lastname: Verbakel
authors.forename: Ben
authors.initials: B
authors.lastname: Slotman
authors.forename: Umberto
authors.initials: U
authors.lastname: Ricardi
authors.forename: Suresh
authors.initials: S
authors.lastname: Senan
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D017564:Radiation Pneumonitis / Q000209:etiology*; D016634:Radiosurgery / Q000009:adverse effects*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects*; D047368:Tumor Burden
keywords: Lung tumors; Radiation pneumonitis; Stereotactic radiotherapy