Re-Irradiation of the Spine with Stereotactic Radiosurgery: Efficacy & Toxicity

Publication date: Available online 25 May 2017
Source:Practical Radiation Oncology
Author(s): David Boyce-Fappiano, Erinma Elibe, Bo Zhao, M. Salim Siddiqui, Ian Lee, Jack Rock, Samuel Ryu, Farzan Siddiqui
PurposeTo determine the potential benefits and adverse effects associated with re-irradiating the spinal cord when at least one course of radiation therapy (RT) is stereotactic radiosurgery (SRS).Methods and MaterialsThis IRB approved retrospective review included 162 patients (237 re-irradiated spine lesions). All patients received SRS at our institution between 2001–2013. Electronic medical records were reviewed for clinical exams and radiologic tests (CT/ MRI). Primary endpoints were pain, neurological, radiographic responses and the development of adverse effects.ResultsOne hundred and twenty patients (74.1%) were deceased with a median survival of 13months, Time between courses of RT was a median of 10.2months. Median SRS dose was 16Gy in 1 fraction while the median conventional external beam radiation therapy (cEBRT) dose was 30Gy in 10 fractions. The median tumor equivalent dose in 2Gy fractions (EQD2) for SRS doses was 34.7Gy while the median tumor EQD2 for cEBRT was 32.5Gy providing a median total tumor EQD2 of 69.3Gy (22Gy – 145.6Gy). The median critical nervous system (CNT) EQD2 for SRS and cEBRT was 56Gy and 37.5Gy respectively resulting in a median total CNT EQD2 of 93.5Gy. Overall pain, neurological, and radiographic response rates were 81%, 82%, and 71% respectively. Adverse effects occurred in 11(6.8%) patients. Seventy-seven vertebral compression fractures (VCFs) were observed, 22 (9.3%) of which may be attributed to RT.ConclusionsOur results demonstrate that re-irradiation achieves favorable response rates with minimal toxicity if recommended dose constraints to the spinal cord with SRS are carefully observed. To the best of our knowledge, this is the largest reported single institution experience analyzing the efficacy and toxicity of re-irradiation of the spine when at least one course of RT is stereotactic radiosurgery.



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