Clinical applicability of biologically effective dose calculation for spinal cord in fractionated spine stereotactic body radiation therapy

Background. The aim of the study was to investigate whether biologically effective dose (BED) based on linearquadratic model can be used to estimate spinal cord tolerance dose in spine stereotactic body radiation therapy (SBRT) delivered in 4 or more fractions. Patients and methods. Sixty-three meta...

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Bibliographic Details
Published in:Radiology and oncology 2015-06, Vol.49 (2), p.185-191
Main Authors: Lee, Seung Heon, Lee, Kyu Chan, Choi, Jinho, Ahn, So Hyun, Lee, Seok Ho, Sung, Ki Hoon, Kil, Se Hee
Format: Article
Language:English
Subjects:
biologically effective dose
linear quadratic model
Metastasis
Radiation therapy
Spinal cord
spine stereotactic body radiation therapy
tolerance dose
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Summary:Background. The aim of the study was to investigate whether biologically effective dose (BED) based on linearquadratic model can be used to estimate spinal cord tolerance dose in spine stereotactic body radiation therapy (SBRT) delivered in 4 or more fractions. Patients and methods. Sixty-three metastatic spinal lesions in 47 patients were retrospectively evaluated. The most frequently prescribed dose was 36 Gy in 4 fractions. In planning, we tried to limit the maximum dose to the spinal cord or cauda equina less than 50% of prescription or 45 Gy . BED was calculated using maximum point dose of spinal cord. Results. Maximum spinal cord dose per fraction ranged from 2.6 to 6.0 Gy (median 4.3 Gy). Except 4 patients with 52.7, 56.4, 62.4, and 67.9 Gy , equivalent total dose in 2-Gy fraction of the patients was not more than 50 Gy (12.1- 67.9, median 32.0). The ratio of maximum spinal cord dose to prescription dose increased up to 82.2% of prescription dose as epidural spinal cord compression grade increased. No patient developed grade 2 or higher radiationinduced spinal cord toxicity during follow-up period of 0.5 to 53.9 months. Conclusions. In fractionated spine SBRT, BED can be used to estimate spinal cord tolerance dose, provided that the dose per fraction to the spinal cord is moderate, e.g. < 6.0 Gy. It appears that a maximum dose of up to 45-50 Gy to the spinal cord is tolerable in 4 or more fractionation regimen.
ISSN:1318-2099
1581-3207
1581-3207
0485-893X
DOI:10.1515/raon-2015-0008