Reirradiation Human Spinal Cord Tolerance for Stereotactic Body Radiotherapy
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, Princess Margaret Hospital, University of Toronto, Toronto (Canada)
- Department of Radiation Oncology, University of California San Francisco, San Francisco, CA (United States)
- University of California San Francisco Helen Diller Family Comprehensive Cancer Center Biostatistics Core, San Francisco, CA (United States)
- Department of Radiation Oncology, Stanford University, Stanford, CA (United States)
- Departments of Radiation Oncology and Neurosurgery, Cleveland Clinic, Cleveland, OH (United States)
- Department of Neurosurgery, Korea Institute of Radiation and Medical Science, Seoul (Korea, Republic of)
- Department of Radiation Oncology, Thomas Jefferson University Hospital, Philadelphia, PA (United States)
- Department of Radiation Oncology, M.D. Anderson Cancer Center, University of Texas, Houston, TX (United States)
- Department of Neurosurgery, Inje University, Seoul (Korea, Republic of)
- Department of Radiation Oncology, Princess Margaret Hospital, University of Toronto, Toronto (Canada)
- Department of Radiation Oncology, Henry Ford Hospital, Detroit, MI (United States)
- Departments of Neurological Surgery and Radiation Oncology, University of Pittsburgh Medical Center, Pittsburgh, PA (United States)
- Departments of Human Oncology and Medical Physics, University of Wisconsin, WI (United States)
- Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto (Canada)
Purpose: We reviewed the treatment for patients with spine metastases who initially received conventional external beam radiation (EBRT) and were reirradiated with 1-5 fractions of stereotactic body radiotherapy (SBRT) who did or did not subsequently develop radiation myelopathy (RM). Methods and Materials: Spinal cord dose-volume histograms (DVHs) for 5 RM patients (5 spinal segments) and 14 no-RM patients (16 spine segments) were based on thecal sac contours at retreatment. Dose to a point within the thecal sac that receives the maximum dose (P{sub max}), and doses to 0.1-, 1.0-, and 2.0-cc volumes within the thecal sac were reviewed. The biologically effective doses (BED) using {alpha}/{beta} = 2 Gy for late spinal cord toxicity were calculated and normalized to a 2-Gy equivalent dose (nBED = Gy{sub 2/2}). Results: The initial conventional radiotherapy nBED ranged from {approx}30 to 50 Gy{sub 2/2} (median {approx}40 Gy{sub 2/2}). The SBRT reirradiation thecal sac mean P{sub max} nBED in the no-RM group was 20.0 Gy{sub 2/2} (95% confidence interval [CI], 10.8-29.2), which was significantly lower than the corresponding 67.4 Gy{sub 2/2} (95% CI, 51.0-83.9) in the RM group. The mean total P{sub max} nBED in the no-RM group was 62.3 Gy{sub 2/2} (95% CI, 50.3-74.3), which was significantly lower than the corresponding 105.8 Gy{sub 2/2} (95% CI, 84.3-127.4) in the RM group. The fraction of the total P{sub max} nBED accounted for by the SBRT P{sub max} nBED for the RM patients ranged from 0.54 to 0.78 and that for the no-RM patients ranged from 0.04 to 0.53. Conclusions: SBRT given at least 5 months after conventional palliative radiotherapy with a reirradiation thecal sac P{sub max} nBED of 20-25 Gy{sub 2/2} appears to be safe provided the total P{sub max} nBED does not exceed approximately 70 Gy{sub 2/2}, and the SBRT thecal sac P{sub max} nBED comprises no more than approximately 50% of the total nBED.
- OSTI ID:
- 22055922
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 82, Issue 1; Other Information: Copyright (c) 2012 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
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