Abstract
More than half of pediatric tumors of central nervous system (CNS) primarily originate in the posterior fossa and are conventionally treated with radiation therapy (RT). The objective of this study was to establish whether corpus callosum volumes (CCV) and whole brain volumes (WBV) are correlated and to determine the impact of whole-brain lowvs high-dose RT on brain parenchymal volume loss as assessed using each technique. Of the 30 identified children (6-12 years) with newly diagnosed posterior fossa tumors treated with cranial RT, including focal and whole-brain RT, suitable imaging was obtained for 23. Radiotherapy regimens were the following: no whole-brain RT (Group 1, n = 7), low-dose whole-brain RT (<30 Gy, Group 2, n = 9) and high-dose whole-brain RT (>30 Gy, Group 3, n = 7) in addition to focal boost. Magnetic resonance images (MRIs) were analyzed at baseline and follow-up (median 14 months). The CCVs were manually segmented on midline sagittal slice (n = 23), while WBVs were segmented semi-automatically using Freesurfer (n = 15). This was done twice (6-month interval) for all baseline CCV measurements and 5 randomly selected WBV measurements to establish measurement reproducibility. Correlations between CCV and WBV were investigated and percentage of children demonstrating reduction in CCV or WBV noted. Correlation between baseline CCV and WBV was not significant (p = 0.37). Measurement reproducibility was from 6% to -9% for CCV and from 4.8% to -1.2% for WBV. Among the children studied, 30.4% (7/23) had >9% reduction in CCV at follow-up, while 33.3% (5/15) had >1.2% reduction in WBV. Five of 7 patients with CCV loss were not picked up by WBV measurements. Similarly, 3 of 5 patients with WBV loss were not picked up by CCV measurements. The CCV and the WBV are unrelated and may indicate different brain parenchymal losses following RT. Up to a third of posterior fossa tumors treated with RT have measurable CCV or WBV loss; incidence was equivalent in lowvs high-dose whole-brain RT.
Highlights
More than half of pediatric tumors of the central nervous system (CNS) primarily originate in the posterior fossa and are conventionally treated with radiation therapy (RT).[1]
The objective of this study was to establish whether corpus callosum volumes (CCV) and whole brain volumes (WBV) are correlated and to determine the impact of whole-brain low- vs high-dose RT on brain parenchymal volume loss as assessed using each technique
Measurement reproducibility was from 6% to –9% for CCV and from 4.8% to –1.2% for WBV
Summary
More than half of pediatric tumors of the central nervous system (CNS) primarily originate in the posterior fossa and are conventionally treated with radiation therapy (RT).[1]. Various degrees of parenchymal volume loss and generalized white matter signal changes have been reported in children treated for medulloblastoma (MDL).[4,5,6,7] Most studies used a fully automated hybrid neural network segmentation as well as a classification method to quantitatively derive volumes of brain parenchyma from these images.[4,7,8] Volumes of the corpus callosum (CC) have been advocated as a surrogate to quantify volumes of neuroparenchyma, because the nearly 180 million myelinated axons within this white matter commissure make it susceptible to radiation-induced damage.[5,9] a correlation between CC volume (CCV) and whole brain volume (WBV) has not been demonstrated. More than half of pediatric tumors of central nervous system (CNS) primarily originate in the posterior fossa and are conventionally treated with radiation therapy (RT)
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