Consensus guidelines for postoperative stereotactic body radiation therapy for spinal metastases: results of an international survey.
OBJECTIVE Although postoperative stereotactic body radiation therapy (SBRT) for spinal metastases is increasingly performed, few guidelines exist for this application. The purpose of this study is to develop consensus guidelines to promote safe and effective treatment for patients with spinal metastases. METHODS Fifteen radiation oncologists and 5 neurosurgeons, representing 19 centers in 4 countries and having a collective experience of more than 1300 postoperative spine SBRT cases, completed a 19-question survey about postoperative spine SBRT practice. Responses were defined as follows: 1) consensus: selected by ≥ 75% of respondents; 2) predominant: selected by 50% of respondents or more; and 3) controversial: no single response selected by a majority of respondents. RESULTS Consensus treatment indications included: radioresistant primary, 1-2 levels of adjacent disease, and previous radiation therapy. Contraindications included: involvement of more than 3 contiguous vertebral bodies, ASIA Grade A status (complete spinal cord injury without preservation of motor or sensory function), and postoperative Bilsky Grade 3 residual (cord compression without any CSF around the cord). For treatment planning, co-registration of the preoperative MRI and postoperative T1-weighted MRI (with or without gadolinium) and delineation of the cord on the T2-weighted MRI (and/or CT myelogram in cases of significant hardware artifact) were predominant. Consensus GTV (gross tumor volume) was the postoperative residual tumor based on MRI. Predominant CTV (clinical tumor volume) practice was to include the postoperative bed defined as the entire extent of preoperative tumor, the relevant anatomical compartment and any residual disease. Consensus was achieved with respect to not including the surgical hardware and incision in the CTV. PTV (planning tumor volume) expansion was controversial, ranging from 0 to 2 mm. The spinal cord avoidance structure was predominantly the true cord. Circumferential treatment of the epidural space and margin for paraspinal extension was controversial. Prescription doses and spinal cord tolerances based on clinical scenario, neurological compromise, and prior overlapping treatments were controversial, but reasonable ranges are presented. Fifty percent of those surveyed practiced an integrated boost to areas of residual tumor and density override for hardware within the beam path. Acceptable PTV coverage was controversial, but consensus was achieved with respect to compromising coverage to meet cord constraint and fractionation to improve coverage while meeting cord constraint. CONCLUSIONS The consensus by spinal radiosurgery experts suggests that postoperative SBRT is indicated for radioresistant primary lesions, disease confined to 1-2 vertebral levels, and/or prior overlapping radiotherapy. The GTV is the postoperative residual tumor, and the CTV is the postoperative bed defined as the entire extent of preoperative tumor and anatomical compartment plus residual disease. Hardware and scar do not need to be included in CTV. While predominant agreement was reached about treatment planning and definition of organs at risk, future investigation will be critical in better understanding areas of controversy, including whether circumferential treatment of the epidural space is necessary, management of paraspinal extension, and the optimal dose fractionation schedules.
Department of Radiation Oncology and Molecular Radiation Sciences, The John Hopkins University, Baltimore, Maryland.
Kristin J
KJ
Redmond
Department of Radiation Oncology, University Hospitals Seidman Cancer Center, Case Comprehensive Cancer Center.
Simon S
SS
Lo
Department of Radiation Oncology, Stanford Cancer Institute, Stanford University, Stanford.
Scott G
SG
Soltys
Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York.
Yoshiya
Y
Yamada
Department of Radiation Oncology, University of California, San Francisco.
Igor J
IJ
Barani
Department of Radiation Oncology, MD Anderson Cancer Center.
Paul D
PD
Brown
Department of Radiation Oncology, Norris Cancer Center and Keck School of Medicine at University of Southern California.
Eric L
EL
Chang
Department of Neurological Surgery and Radiation Oncology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
Peter C
PC
Gerszten
Department of Radiation Oncology, Rose Ella Burkhardt Brain Tumor and Neurooncology Center, Cleveland Clinic, Cleveland, Ohio.
Samuel T
ST
Chao
Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, Florida.
Robert J
RJ
Amdur
Department of Neurological Surgery, Brain Research Institute, University of California, Los Angeles, California.
Antonio A F
AA
De Salles
Department of Radiation Oncology, University of Zurich, Switzerland.
Matthias
M
Guckenberger
Department of Radiation Oncology, Houston Methodist Hospital, Cancer Center and Research Institute, Weill Cornell Medical College, Houston, Texas.
Bin S
BS
Teh
Department of Neurological Surgery, University of Virginia Health System, Charlottesville.
Jason
J
Sheehan
Department of Radiation Oncology, Riverside Radiation Oncology Specialists, Newport News, Virginia.
Charles R
CR
Kersh
Division of Neurosurgery and Spine Program, Toronto Western Hospital, University of Toronto.
Michael G
MG
Fehlings
Department of Neurological Surgery, Radiosurgery Center, Inje University Ilsan Paik Hospital, College of Medicine, Goyang; and.
Moon-Jun
MJ
Sohn
Department of Neurosurgery, Korea Institute of Radiological and Medical Sciences, Seoul, South Korea.
Ung-Kyu
UK
Chang
Department of Radiation Oncology, Stony Brook Cancer Center, Stony Brook, New York.
Samuel
S
Ryu
Department of Radiation Oncology, Stanford Cancer Institute, Stanford University, Stanford.
Iris C
IC
Gibbs
Department of Radiation Oncology, Sunnybrook Health Sciences Center, University of Toronto, Toronto, Ontario, Canada.
Arjun
A
Sahgal
D032921:Consensus; D019583:Dose Fractionation, Radiation; D006801:Humans; D009362:Neoplasm Metastasis; D011184:Postoperative Period; D017410:Practice Guidelines as Topic; D016634:Radiosurgery / Q000379:methods; D013117:Spinal Cord Compression / Q000175:diagnosis / Q000209:etiology / Q000601:surgery*; D013125:Spinal Neoplasms / Q000175:diagnosis / Q000532:radiotherapy* / Q000556:secondary / Q000601:surgery*; D011795:Surveys and Questionnaires
ASIA = American Spinal Injury Association; CTV = clinical tumor volume; GTV = gross tumor volume; MESCC = malignant epidural spinal cord compression; PRV = planning risk volume; PTV = planning target volume; RT = radiation therapy; RTOG = Radiation Therapy Oncology Group; SBRT; SBRT = stereotactic body radiation therapy; consensus guidelines; oncology; postoperative spine stereotactic body radiation therapy; spinal metastases