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Radiother Oncol. 2013 Jan;106(1):101-5. doi: 10.1016/j.radonc.2012.08.007. Epub 2012 Sep 14.

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

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  • 1Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, TX 75390-8542, USA. Paul.medin@utsouthwestern.edu

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 ED(50)'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.

Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

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