title: Salvage Stereotactic Body Radiotherapy (SBRT) Following In-Field Failure of Initial SBRT for Spinal Metastases.
abstract: OBJECTIVE
  We report our experience in salvaging spinal metastases initially irradiated with stereotactic body radiation therapy (SBRT), who subsequently progressed with imaging-confirmed local tumor progression, and were re-irradiated with a salvage second SBRT course to the same level.
  
  
  METHODS
  From a prospective database, 56 metastatic spinal segments in 40 patients were identified as having been irradiated with a salvage second SBRT course to the same level. In addition, 24 of 56 (42.9%) segments had initially been irradiated with conventional external beam radiation therapy before the first course of SBRT. Local control (LC) was defined as no progression on magnetic resonance imaging at the treated segment, and calculated according to the competing risk model. Overall survival (OS) was evaluated for each patient treated by use of the Kaplan-Meier method.
  
  
  RESULTS
  The median salvage second SBRT total dose and number of fractions was 30 Gy in 4 fractions (range, 20-35 Gy in 2-5 fractions), and for the first course of SBRT was 24 Gy in 2 fractions (range, 20-35 Gy in 1-5 fractions). The median follow-up time after salvage second SBRT was 6.8 months (range, 0.9-39 months), the median OS was 10.0 months, and the 1-year OS rate was 48%. A longer time interval between the first and second SBRT courses predicted for better OS (P=.02). The crude LC was 77% (43/56), the 1-year LC rate was 81%, and the median time to local failure was 3.0 months (range, 2.7-16.7 months). Of the 13 local failures, 85% (11/13) and 46% (6/13) showed progression within the epidural space and paraspinal soft tissues, respectively. Absence of baseline paraspinal disease predicted for better LC (P<.01). No radiation-induced vertebral compression fractures or cases of myelopathy were observed.
  
  
  CONCLUSIONS
  A second course of spine SBRT, most often with 30 Gy in 4 fractions, for spinal metastases that failed initial SBRT is a feasible and efficacious salvage treatment option.
authors.affiliation: Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Thibault
authors.affiliation: Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Mikki
authors.initials: M
authors.lastname: Campbell
authors.affiliation: Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Chia-Lin
authors.initials: CL
authors.lastname: Tseng
authors.affiliation: Department of Biostatistics, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Eshetu G
authors.initials: EG
authors.lastname: Atenafu
authors.affiliation: Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Daniel
authors.initials: D
authors.lastname: Letourneau
authors.affiliation: Department of Radiology, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Eugene
authors.initials: E
authors.lastname: Yu
authors.affiliation: Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: B C John
authors.initials: BC
authors.lastname: Cho
authors.affiliation: Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Young K
authors.initials: YK
authors.lastname: Lee
authors.affiliation: Department of Radiology, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Fehlings
authors.affiliation: Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada. Electronic address: arjun.sahgal@sunnybrook.ca.
authors.forename: Arjun
authors.initials: A
authors.lastname: Sahgal
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D019583:Dose Fractionation, Radiation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery / Q000379:methods* / Q000401:mortality; D000069475:Re-Irradiation / Q000379:methods; D016879:Salvage Therapy / Q000379:methods* / Q000401:mortality; D013125:Spinal Neoplasms / Q000401:mortality / Q000556:secondary* / Q000601:surgery*; D013997:Time Factors; D017211:Treatment Failure; D055815:Young Adult