title: Estimated Risk Level of Unified Stereotactic Body Radiation Therapy Dose Tolerance Limits for Spinal Cord.
abstract: A literature review of more than 200 stereotactic body radiation therapy spine articles from the past 20 years found only a single article that provided dose-volume data and outcomes for each spinal cord of a clinical dataset: the Gibbs 2007 article (Gibbs et al, 2007(1)), which essentially contains the first 100 stereotactic body radiation therapy (SBRT) spine treatments from Stanford University Medical Center. The dataset is modeled and compared in detail to the rest of the literature review, which found 59 dose tolerance limits for the spinal cord in 1-5 fractions. We partitioned these limits into a unified format of high-risk and low-risk dose tolerance limits. To estimate the corresponding risk level of each limit we used the Gibbs 2007 clinical spinal cord dose-volume data for 102 spinal metastases in 74 patients treated by spinal radiosurgery. In all, 50 of the patients were previously irradiated to a median dose of 40Gy in 2-3Gy fractions and 3 patients developed treatment-related myelopathy. These dose-volume data were digitized into the dose-volume histogram (DVH) Evaluator software tool where parameters of the probit dose-response model were fitted using the maximum likelihood approach (Jackson et al, 1995(3)). Based on this limited dataset, for de novo cases the unified low-risk dose tolerance limits yielded an estimated risk of spinal cord injury of ≤1% in 1-5 fractions, and the high-risk limits yielded an estimated risk of ≤3%. The QUANTEC Dmax limits of 13Gy in a single fraction and 20Gy in 3 fractions had less than 1% risk estimated from this dataset, so we consider these among the low-risk limits. In the previously irradiated cohort, the estimated risk levels for 10 and 14Gy maximum cord dose limits in 5 fractions are 0.4% and 0.6%, respectively. Longer follow-up and more patients are required to improve the risk estimates and provide more complete validation.
authors.affiliation: Bott Cancer Center, Holy Redeemer Hospital, Meadowbrook, PA. Electronic address: jimmgrimmjr@yahoo.com.
authors.forename: Jimm
authors.initials: J
authors.lastname: Grimm
authors.affiliation: Sunnybrook Health Sciences Center, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Arjun
authors.initials: A
authors.lastname: Sahgal
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, CA.
authors.forename: Scott G
authors.initials: SG
authors.lastname: Soltys
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, CA.
authors.forename: Gary
authors.initials: G
authors.lastname: Luxton
authors.affiliation: Department of Radiation Oncology, MD Anderson Cancer Center at Cooper University Hospital, Camden, NJ.
authors.forename: Ashish
authors.initials: A
authors.lastname: Patel
authors.affiliation: Division of Radiation Oncology, Abington Memorial Hospital, Abington, PA.
authors.forename: Scott
authors.initials: S
authors.lastname: Herbert
authors.affiliation: Department of Radiation Oncology, MD Anderson Cancer Center at Cooper University Hospital, Camden, NJ.
authors.forename: Jinyu
authors.initials: J
authors.lastname: Xue
authors.affiliation: Department of Radiation Oncology, University of California at San Francisco, San Francisco, CA.
authors.forename: Lijun
authors.initials: L
authors.lastname: Ma
authors.affiliation: Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Ellen
authors.initials: E
authors.lastname: Yorke
authors.affiliation: Department of Neurosurgery, Stanford University, Stanford, CA.
authors.forename: John R
authors.initials: JR
authors.lastname: Adler
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, CA.
authors.forename: Iris C
authors.initials: IC
authors.lastname: Gibbs
mesh_terms: D006801:Humans; D011832:Radiation Injuries / Q000517:prevention & control; D011836:Radiation Tolerance; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D012306:Risk; D013116:Spinal Cord / Q000528:radiation effects*