Spinal Radiosurgery: Delayed Radiation-Induced Myelopathy
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Spinal cord dose parameters to minimize the risk of radiation myelopathy are relatively well-defined in the conventionally fractionated setting, but remain controversial for the high dose-per-fraction, partial-cord dosimetry encountered in stereotactic radiosurgery (SRS). Myelopathy has been only rarely described in the setting of SRS, and a variety of suggested dose constraints exist in the literature, ranging from a maximum cord dose (cord Dmax) of 10 to 14 Gy or a partial volume tolerance of 10 Gy (V10) to 10% of the contoured cord. Ever-improving attempts at normal tissue complication probability (NCTP) modeling permit estimation of the potential toxicity of high dose-per-fraction regimens, while animal models provide additional insights on a partial cord volume tolerance model for radiation myelopathy and suggest regional differences in radiation sensitivity across the spinal cord. The literature to date contains only ten reported cases of SRS-induced myelopathy; however, with increasing use of SRS for both benign and metastatic lesions of the spine, refining our understanding of the tolerance of the human spinal cord to hypofractionated dosimetry remains crucial.
KeywordsSpinal Cord Biologically Effective Dose Normal Tissue Complication Probability Linear Quadratic Model Radiation Myelopathy
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