Spinal Cord Dose Tolerance to Stereotactic Body Radiation Therapy.

Sahgal, Arjun; Chang, Joe H; Ma, Lijun; Marks, Lawrence B; Milano, Michael T; Medin, Paul; Niemierko, Andrzej; Soltys, Scott G et al. · Int J Radiat Oncol Biol Phys · 2021

review · Level V

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Abstract

Spinal cord tolerance data for stereotactic body radiation therapy (SBRT) were extracted from published reports, reviewed, and modelled. For de novo SBRT delivered in 1 to 5 fractions, the following spinal cord point maximum doses (D<sub>max</sub>) are estimated to be associated with a 1% to 5% risk of radiation myelopathy (RM): 12.4 to 14.0 Gy in 1 fraction, 17.0 Gy in 2 fractions, 20.3 Gy in 3 fractions, 23.0 Gy in 4 fractions, and 25.3 Gy in 5 fractions. For reirradiation SBRT delivered in 1 to 5 fractions, reported factors associated with a lower risk of RM include cumulative thecal sac equivalent dose in 2 Gy fractions with an alpha/beta of 2 (EQD2<sub>2</sub>) D<sub>max</sub> ≤70 Gy; SBRT thecal sac EQD2<sub>2</sub> D<sub>max</sub> ≤25 Gy, thecal sac SBRT EQD2<sub>2</sub> D<sub>max</sub> to cumulative EQD2<sub>2</sub> D<sub>max</sub> ratio ≤0.5, and a minimum time interval to reirradiation of ≥5 months. Larger studies containing complete institutional cohorts with dosimetric data of patients treated with spine SBRT, with and without RM, are required to refine RM risk estimates.

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