title: Volume specific response criteria for brain metastases following salvage stereotactic radiosurgery and associated predictors of response.
abstract: BACKGROUND
  We aimed to derive three-dimensional volume-based (V(3D)) response criteria that approximate those based on Response Evaluation Criteria in Solid Tumours (RECIST) in patients with brain metastases (BM) treated with salvage stereotactic radiosurgery (SRS).
  
  
  METHODS
  Seventy patients with 178 BM were treated with SRS. Each BM was characterised at baseline and at each follow-up MRI according to its widest diameter and V(3D) using ITK-SNAP image segmentation software.
  
  
  RESULTS
  The median tumour diameter was 1.2 cm (range, 0.2-4.5 cm) and V(3D) was 0.73 cm(3) (range, 0.01-22.7 cm(3)). The V(3D) percent changes that best matched RECIST response criteria were: an increase of ≥71.5% for progressive disease, a ≥58.5% decrease for partial response and a <58.5% decrease or increase of <71.5% for stable disease (k =0.85). A baseline diameter >3.0 cm (p =0.006) and a V(3D) >6.0 cm(3) (p =0.043) predicted for local failure, and a baseline cumulative V(3D) of >3.0 cm(3) (p =0.02) was adversely prognostic for survival.
  
  
  CONCLUSIONS
  We define 3D volume specific criteria to base response upon for brain metastases treated with salvage SRS. Tumours with a V(3D) of greater than 6 cm(3) are at a higher risk of local failure.
authors.affiliation: Department of Radiation Oncology, Princess Margaret Hospital, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Follwell
authors.forename: Kathleen J
authors.initials: KJ
authors.lastname: Khu
authors.forename: Lu
authors.initials: L
authors.lastname: Cheng
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.forename: David J
authors.initials: DJ
authors.lastname: Mikulis
authors.forename: Barbara-Ann
authors.initials: BA
authors.lastname: Millar
authors.forename: May N
authors.initials: MN
authors.lastname: Tsao
authors.forename: Normand J
authors.initials: NJ
authors.lastname: Laperriere
authors.forename: Mark
authors.initials: M
authors.lastname: Bernstein
authors.forename: Arjun
authors.initials: A
authors.lastname: Sahgal
mesh_terms: D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000401:mortality / Q000556:secondary* / Q000601:surgery*; D019583:Dose Fractionation, Radiation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000401:mortality / Q000473:pathology / Q000601:surgery*; D011379:Prognosis; D016634:Radiosurgery; D012189:Retrospective Studies; D016879:Salvage Therapy; D015996:Survival Rate; D047368:Tumor Burden