title: International Spine Radiosurgery Consortium consensus guidelines for target volume definition in spinal stereotactic radiosurgery.
abstract: OBJECTIVE
  Spinal stereotactic radiosurgery (SRS) is increasingly used to manage spinal metastases. However, target volume definition varies considerably and no consensus target volume guidelines exist. This study proposes consensus target volume definitions using common scenarios in metastatic spine radiosurgery.
  
  
  METHODS
  Seven radiation oncologists and 3 neurological surgeons with spinal radiosurgery expertise independently contoured target and critical normal structures for 10 cases representing common scenarios in metastatic spine radiosurgery. Each set of volumes was imported into the Computational Environment for Radiotherapy Research. Quantitative analysis was performed using an expectation maximization algorithm for Simultaneous Truth and Performance Level Estimation (STAPLE) with kappa statistics calculating agreement between physicians. Optimized confidence level consensus contours were identified using histogram agreement analysis and characterized to create target volume definition guidelines.
  
  
  RESULTS
  Mean STAPLE agreement sensitivity and specificity was 0.76 (range, 0.67-0.84) and 0.97 (range, 0.94-0.99), respectively, for gross tumor volume (GTV) and 0.79 (range, 0.66-0.91) and 0.96 (range, 0.92-0.98), respectively, for clinical target volume (CTV). Mean kappa agreement was 0.65 (range, 0.54-0.79) for GTV and 0.64 (range, 0.54-0.82) for CTV (P<.01 for GTV and CTV in all cases). STAPLE histogram agreement analysis identified optimal consensus contours (80% confidence limit). Consensus recommendations include that the CTV should include abnormal marrow signal suspicious for microscopic invasion and an adjacent normal bony expansion to account for subclinical tumor spread in the marrow space. No epidural CTV expansion is recommended without epidural disease, and circumferential CTVs encircling the cord should be used only when the vertebral body, bilateral pedicles/lamina, and spinous process are all involved or there is extensive metastatic disease along the circumference of the epidural space.
  
  
  CONCLUSIONS
  This report provides consensus guidelines for target volume definition for spinal metastases receiving upfront SRS in common clinical situations.
authors.affiliation: Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York, USA. coxb@mskcc.org
authors.forename: Brett W
authors.initials: BW
authors.lastname: Cox
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Spratt
authors.forename: Michael
authors.initials: M
authors.lastname: Lovelock
authors.forename: Mark H
authors.initials: MH
authors.lastname: Bilsky
authors.forename: Eric
authors.initials: E
authors.lastname: Lis
authors.forename: Samuel
authors.initials: S
authors.lastname: Ryu
authors.forename: Jason
authors.initials: J
authors.lastname: Sheehan
authors.forename: Peter C
authors.initials: PC
authors.lastname: Gerszten
authors.forename: Eric
authors.initials: E
authors.lastname: Chang
authors.forename: Iris
authors.initials: I
authors.lastname: Gibbs
authors.forename: Scott
authors.initials: S
authors.lastname: Soltys
authors.forename: Arjun
authors.initials: A
authors.lastname: Sahgal
authors.forename: Joe
authors.initials: J
authors.lastname: Deasy
authors.forename: John
authors.initials: J
authors.lastname: Flickinger
authors.forename: Mubina
authors.initials: M
authors.lastname: Quader
authors.forename: Stefan
authors.initials: S
authors.lastname: Mindea
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Yamada
mesh_terms: D006801:Humans; D008159:Lumbar Vertebrae / Q000473:pathology; D008279:Magnetic Resonance Imaging; D016634:Radiosurgery / Q000592:standards*; D013125:Spinal Neoplasms / Q000473:pathology / Q000556:secondary* / Q000601:surgery*; D013904:Thoracic Vertebrae / Q000473:pathology; D047368:Tumor Burden