NCOG-45. DIFFERENTIAL AND DOSE-DEPENDENT EFFECTS OF CRANIAL IRRADIATION ON BRAIN STRUCTURES AND NEUROPSYCHOLOGICAL OUTCOMES IN CHILDREN WITH POSTERIOR FOSSA BRAIN TUMORS TREATED WITH DIFFERENT MODALITIES

Abstract BACKGROUND Studies investigating dose-dependent effects of cranial irradiation (CRT) in children with posterior fossa brain tumors are limited by examining combined surgery, chemotherapy, and radiation. We aimed to determine alterations volume microstructure, neuropsychological outcomes treated surgery alone, CRT combined. explored the relationship radiation dose thalamus, putamen, hippocampus intelligence, processing speed, executive functions, memory, social/emotional functioning. METHODS Forty-seven (17 surgery; 11 chemotherapy; 19 CRT) underwent neuroimaging assessment a mean 4.8 years after treatment, along 17 healthy sibling controls (n=64). The thalamus were manually segmented on MRI, structural doses calculated. Differences demographics medical history evaluated using χ2 t-tests. Linear regression examined differences performance, volumes, diffusion indices. Pearson correlation relationships indices outcomes. RESULTS All patients scored lower Block Design than (p=0.01), chemotherapy group lowest. There was no significant difference fractional anisotropy (FA) values putamen between three patient groups controls. Hippocampal approached (r= -0.49; p=0.07). Right FA correlated (r=0.56; p=0.02). When controlling for age, thalamic lowest irradiated (p=0.02). CONCLUSIONS Treatment pediatric impacts may have effect microstructure compared treatment surgery/chemotherapy.