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Int J Radiat Oncol Biol Phys. 2017 Feb 1;97(2):263-269. doi: 10.1016/j.ijrobp.2016.10.035. Epub 2016 Oct 31.

Radiation Dose-Dependent Hippocampal Atrophy Detected With Longitudinal Volumetric Magnetic Resonance Imaging.

Author information

1
Department of Radiation Medicine and Applied Sciences, University of California, San Diego, La Jolla, California.
2
Department of Radiology, University of California, San Diego, La Jolla, California.
3
Department of Radiology, University of California, San Diego, La Jolla, California; Department of Neurosciences, University of California, San Diego, La Jolla, California.
4
Department of Psychiatry, University of California, San Diego, La Jolla, California.
5
Department of Radiation Medicine and Applied Sciences, University of California, San Diego, La Jolla, California. Electronic address: jhattangadi@ucsd.edu.

Abstract

PURPOSE:

After radiation therapy (RT) to the brain, patients often experience memory impairment, which may be partially mediated by damage to the hippocampus. Hippocampal sparing in RT planning is the subject of recent and ongoing clinical trials. Calculating appropriate hippocampal dose constraints would be improved by efficient in vivo measurements of hippocampal damage. In this study we sought to determine whether brain RT was associated with dose-dependent hippocampal atrophy.

METHODS AND MATERIALS:

Hippocampal volume was measured with magnetic resonance imaging (MRI) in 52 patients who underwent fractionated, partial brain RT for primary brain tumors. Study patients had high-resolution, 3-dimensional volumetric MRI before and 1 year after RT. Images were processed using software with clearance from the US Food and Drug Administration and Conformité Européene marking for automated measurement of hippocampal volume. Automated results were inspected visually for accuracy. Tumor and surgical changes were censored. Mean hippocampal dose was tested for correlation with hippocampal atrophy 1 year after RT. Average hippocampal volume change was also calculated for hippocampi receiving high (>40 Gy) or low (<10 Gy) mean RT dose. A multivariate analysis was conducted with linear mixed-effects modeling to evaluate other potential predictors of hippocampal volume change, including patient (random effect), age, hemisphere, sex, seizure history, and baseline volume. Statistical significance was evaluated at α = 0.05.

RESULTS:

Mean hippocampal dose was significantly correlated with hippocampal volume loss (r=-0.24, P=.03). Mean hippocampal volume was significantly reduced 1 year after high-dose RT (mean -6%, P=.009) but not after low-dose RT. In multivariate analysis, both RT dose and patient age were significant predictors of hippocampal atrophy (P<.01).

CONCLUSIONS:

The hippocampus demonstrates radiation dose-dependent atrophy after treatment for brain tumors. Quantitative MRI is a noninvasive imaging technique capable of measuring radiation effects on intracranial structures. This technique could be investigated as a potential biomarker for development of reliable dose constraints for improved cognitive outcomes.

Comment in

PMID:
28068234
PMCID:
PMC5267344
DOI:
10.1016/j.ijrobp.2016.10.035
[Indexed for MEDLINE]
Free PMC Article

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