title: Optimizing SABR delivery for synchronous multiple lung tumors using volumetric-modulated arc therapy.
abstract: BACKGROUND
  Volumetric-modulated arc therapy (VMAT) delivery for stereotactic ablative radiotherapy (SABR) of multiple lung tumors allows for faster treatments. We report on clinical outcomes and describe a general approach for treatment planning.
  
  
  METHODS
  Patients undergoing multi iso-center VMAT-based SABR for ≥2 lung lesions between 2009 and 2014 were identified from the VU University Medical Center and London Health Sciences Centre. Patients were eligible if the start date of the SABR treatment for the different lesions was within a time range of 30 days. SABR was delivered using separate iso-centers for lesions at a substantial distance from each other. Tumors were either treated with a single fraction of 34 Gy, or using three risk-adapted dose-fractionation schemes, namely three fractions of 18 Gy, five fractions of 11 Gy, or eight fractions of 7.5 Gy, depending on the tumor size and the location. Multivariable analysis was performed to assess factors predictive of clinical outcomes.
  
  
  RESULTS
  Of 84 patients (188 lesions) identified, 46% were treated for multiple metastases and 54% for multiple primary NSCLC. About 97% were treated for two or three lesions, and 56% had bilateral disease. After a median follow-up of 28 months, median overall survival (OS) for primary tumors was 27.6 months, and not reached for metastatic lesions (p = .028). Grade ≥3 toxicity was observed in 2% of patients. Multivariable analysis showed that grade 2 or higher radiation pneumonitis (n = 9) was best predicted by a total lung V35Gyof ≥6.5% (in 2Gy/fraction equivalent) (p = .007).
  
  
  CONCLUSIONS
  Severe toxicity was uncommon following SABR using VMAT for up to three lung tumors. Further investigations of planning parameters are needed in patients presenting with more lesions.
authors.affiliation: a Department of Radiation Oncology , VU University Medical Center , Amsterdam , The Netherlands.
authors.forename: Hilâl
authors.initials: H
authors.lastname: Tekatli
authors.affiliation: a Department of Radiation Oncology , VU University Medical Center , Amsterdam , The Netherlands.
authors.forename: Shyama U
authors.initials: SU
authors.lastname: Tetar
authors.affiliation: b Department of Radiation Oncology , London Health Sciences Centre , London , Ontario , Canada.
authors.forename: Timothy K
authors.initials: TK
authors.lastname: Nguyen
authors.affiliation: b Department of Radiation Oncology , London Health Sciences Centre , London , Ontario , Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Warner
authors.affiliation: a Department of Radiation Oncology , VU University Medical Center , Amsterdam , The Netherlands.
authors.forename: Wilko F
authors.initials: WF
authors.lastname: Verbakel
authors.affiliation: b Department of Radiation Oncology , London Health Sciences Centre , London , Ontario , Canada.
authors.forename: David A
authors.initials: DA
authors.lastname: Palma
authors.affiliation: a Department of Radiation Oncology , VU University Medical Center , Amsterdam , The Netherlands.
authors.forename: Max
authors.initials: M
authors.lastname: Dahele
authors.affiliation: b Department of Radiation Oncology , London Health Sciences Centre , London , Ontario , Canada.
authors.forename: Stewart
authors.initials: S
authors.lastname: Gaede
authors.affiliation: a Department of Radiation Oncology , VU University Medical Center , Amsterdam , The Netherlands.
authors.forename: Cornelis
authors.initials: C
authors.lastname: Haasbeek
authors.affiliation: a Department of Radiation Oncology , VU University Medical Center , Amsterdam , The Netherlands.
authors.forename: Femke O
authors.initials: FO
authors.lastname: Spoelstra
authors.affiliation: a Department of Radiation Oncology , VU University Medical Center , Amsterdam , The Netherlands.
authors.forename: Patricia F
authors.initials: PF
authors.lastname: de Haan
authors.affiliation: a Department of Radiation Oncology , VU University Medical Center , Amsterdam , The Netherlands.
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Slotman
authors.affiliation: a Department of Radiation Oncology , VU University Medical Center , Amsterdam , The Netherlands.
authors.forename: Suresh
authors.initials: S
authors.lastname: Senan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008175:Lung Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*