International Spine Radiosurgery Consortium Consensus Guidelines for Target Volume Definition in Spinal Stereotactic Radiosurgery

• DOI: 10.1016/j.ijrobp.2012.03.009
• Publication Date: 2012-07-07T03:26:36Z
• Authors: Brett W. Cox; Daniel E. Spratt; Michael Lovelock; Mark H. Bilsky; Eric Lis; Samuel Ryu; Jason Sheehan; Peter C. Gerszten; Eric Chang; Iris Gibbs; Scott Soltys; Arjun Sahgal; Joe Deasy; John Flickinger; Mubina Quader; Stefan Mindea; Yoshiya Yamada
• Keywords: 03 medical and health sciences; Lumbar Vertebrae; Spinal Neoplasms; 0302 clinical medicine; Humans; Radiosurgery; Magnetic Resonance Imaging; Thoracic Vertebrae; Tumor Burden; 3. Good health

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.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.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.This report provides consensus guidelines for target volume definition for spinal metastases receiving upfront SRS in common clinical situations.