SU-E-J-143: Short- and Near-Term Effects of Proton Therapy On Cerebral White Matter

Authors


Abstract

Purpose:

To assess early effects of proton therapy on the structural integrity of cerebral white matter in relation to the subsequent near-term development of such effects.

Methods:

Sixteen children (aged 2–19 years) with craniopharyngioma underwent proton therapy of 54 Cobalt Gray Equivalent (CGE) in a prospective therapeutic trial. Diffusion tensor imaging (DTI) was performed at baseline before proton therapy and every 3 months thereafter. Tract-based spatial statics analysis of DTI data was performed to derive the fractional anisotropy (FA) and radial diffusivity (RD) in 26 volumes of interest (VOIs). The dose distributions were spatially normalized to identify VOIs prone to high doses. The longitudinal percentage changes of the FA and RD in these VOIs at 3 and 12 months from the baseline were calculated, and their relationships were evaluated.

Results:

The average dose was highest to the cerebral peduncle (CP), corticospinal tract (CST) in the pons, pontine crossing tract (PCT), anterior/posterior limbs of the internal capsule (ALIC/PLIC), and genu of the corpus callosum (GCC). It ranged from 33.3 GCE (GCC) to 49.7 GCE (CP). A mild but statistically significant (P<0.05) decline of FA was observed 3 months after proton therapy in all VOIs except the PLIC and ranged from −1.7% (ALIC) to −2.8% (PCT). A significant increase of RD was found in the CP (3.5%) and ALIC (2.1%). The average longitudinal change from the baseline was reduced at 12 months for most VOIs. However, the standard deviation increased, indicating that the temporal pattern varied individually. The follow-up measurements at 3 and 12 months correlated for the CP, CST, PCT, and GCC (P < 0.04).

Conclusion:

DTI data suggest early (3 months) effects of proton therapy on microstructures in the white matter. The subsequent follow-up indicated individual variation of the changes, which was partly implied by the early effects.

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