Spinal cord tolerance to single-session uniform irradiation in pigs: Implications for a dose-volume effect

Abstract Background and purpose This study was performed to test the hypothesis that spinal cord radiosensitivity is significantly modified by uniform versus laterally non-uniform dose distributions. Materials and methods A uniform dose distribution was delivered to a 4.5–7.0 cm length of cervical s...

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Published in:Radiotherapy and oncology 2013-01, Vol.106 (1), p.101-105
Main Authors: Medin, Paul M, Foster, Ryan D, van der Kogel, Albert J, Sayre, James W, McBride, William H, Solberg, Timothy D
Format: Article
Language:English
Subjects:
Animals
Dose-Response Relationship, Radiation
Dose-volume effect
Female
Hematology, Oncology and Palliative Medicine
Normal tissue tolerance
Radiation Dosage
Radiation Tolerance
Spinal Cord - radiation effects
Spinal cord tolerance
Stereotactic spinal radiosurgery
Swine
Swine, Miniature
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Summary:Abstract Background and purpose This study was performed to test the hypothesis that spinal cord radiosensitivity is significantly modified by uniform versus laterally non-uniform dose distributions. Materials and methods A uniform dose distribution was delivered to a 4.5–7.0 cm length of cervical spinal cord in 22 mature Yucatan minipigs for comparison with a companion study in which a laterally non-uniform dose was given [1] . Pigs were allocated into four dose groups with mean maximum spinal cord doses of 17.5 ± 0.1 Gy ( n = 7), 19.5 ± 0.2 Gy ( n = 6), 22.0 ± 0.1 Gy ( n = 5), and 24.1 ± 0.2 Gy ( n = 4). The study endpoint was motor neurologic deficit determined by a change in gait within one year. Spinal cord sections were stained with a Luxol fast blue/periodic acid Schiff combination. Results Dose–response curves for uniform versus non-uniform spinal cord irradiation were nearly identical with ED50 ’s (95% confidence interval) of 20.2 Gy (19.1–25.8) and 20.0 Gy (18.3–21.7), respectively. No neurologic change was observed for either dose distribution when the maximum spinal cord dose was ⩽17.8 Gy while all animals experienced deficits at doses ⩾21.8 Gy. Conclusion No dose-volume effect was observed in pigs for the dose distributions studied and the endpoint of motor neurologic deficit; however, partial spinal cord irradiation resulted in less debilitating neurologic morbidity and histopathology.
ISSN:0167-8140
1879-0887
DOI:10.1016/j.radonc.2012.08.007