title: Volume of Lytic Vertebral Body Metastatic Disease Quantified Using Computed Tomography-Based Image Segmentation Predicts Fracture Risk After Spine Stereotactic Body Radiation Therapy.
abstract: To determine a threshold of vertebral body (VB) osteolytic or osteoblastic tumor involvement that would predict vertebral compression fracture (VCF) risk after stereotactic body radiation therapy (SBRT), using volumetric image-segmentation software.
  
  
  
  A computational semiautomated skeletal metastasis segmentation process refined in our laboratory was applied to the pretreatment planning CT scan of 100 vertebral segments in 55 patients treated with spine SBRT. Each VB was segmented and the percentage of lytic and/or blastic disease by volume determined.
  
  
  
  The cumulative incidence of VCF at 3 and 12 months was 14.1% and 17.3%, respectively. The median follow-up was 7.3 months (range, 0.6-67.6 months). In all, 56% of segments were determined lytic, 23% blastic, and 21% mixed, according to clinical radiologic determination. Within these 3 clinical cohorts, the segmentation-determined mean percentages of lytic and blastic tumor were 8.9% and 6.0%, 0.2% and 26.9%, and 3.4% and 15.8% by volume, respectively. On the basis of the entire cohort (n=100), a significant association was observed for the osteolytic percentage measures and the occurrence of VCF (P<.001) but not for the osteoblastic measures. The most significant lytic disease threshold was observed at ≥11.6% (odds ratio 37.4, 95% confidence interval 9.4-148.9). On multivariable analysis, ≥11.6% lytic disease (P<.001), baseline VCF (P<.001), and SBRT with ≥20 Gy per fraction (P=.014) were predictive.
  
  
  
  Pretreatment lytic VB disease volumetric measures, independent of the blastic component, predict for SBRT-induced VCF. Larger-scale trials evaluating our software are planned to validate the results.
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Centre Hospitalier de L'Universite de Québec-Université Laval, Quebec, Quebec, Canada.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Thibault
authors.affiliation: Orthopaedic Biomechanics Laboratory, Sunnybrook Research Institute, Department of Surgery, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Cari M
authors.initials: CM
authors.lastname: Whyne
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Zhou
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Mikki
authors.initials: M
authors.lastname: Campbell
authors.affiliation: Department of Biostatistics, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Eshetu G
authors.initials: EG
authors.lastname: Atenafu
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Sten
authors.initials: S
authors.lastname: Myrehaug
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Hany
authors.initials: H
authors.lastname: Soliman
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Young K
authors.initials: YK
authors.lastname: Lee
authors.affiliation: Orthopaedic Biomechanics Laboratory, Sunnybrook Research Institute, Department of Surgery, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Hamid
authors.initials: H
authors.lastname: Ebrahimi
authors.affiliation: Division of Orthopaedic Surgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Albert J M
authors.initials: AJ
authors.lastname: Yee
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada. Electronic address: arjun.sahgal@sunnybrook.ca.
authors.forename: Arjun
authors.initials: A
authors.lastname: Sahgal
mesh_terms: D002574:Cervical Vertebrae / Q000000981:diagnostic imaging; D005260:Female; D005500:Follow-Up Studies; D050815:Fractures, Compression / Q000453:epidemiology / Q000209:etiology*; D006801:Humans; D015994:Incidence; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D008297:Male; D010014:Osteolysis / Q000150:complications / Q000000981:diagnostic imaging*; D016634:Radiosurgery / Q000009:adverse effects*; D011879:Radiotherapy Dosage; D018570:Risk Assessment / Q000379:methods; D012984:Software; D016103:Spinal Fractures / Q000453:epidemiology / Q000209:etiology*; D013125:Spinal Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy / Q000556:secondary*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging; D013997:Time Factors; D014057:Tomography, X-Ray Computed