QOS-58IMPACT OF CRANIAL RADIATION THERAPY ON HIPPOCAMPAL SUBFIELD VOLUMES AND DECLARATIVE MEMORY IN PEDIATRIC BRAIN TUMOR SURVIVORS

Abstract

QOS-58. IMPACT OF CRANIAL RADIATION THERAPY ON HIPPOCAMPAL SUBFIELD VOLUMES AND DECLARATIVE MEMORY IN PEDIATRIC BRAIN TUMOR SURVIVORS Alexandra Decker1,2, Kamila Szulc1, Jovanka Skocic1, Cynthia de Medeiros1, Lily Riggs1, Eric Bouffet3, Colleen Dockstader1,2, Suzanne Laughlin4, M. Mallar Chakravarty5,6, and Donald Mabbott1,2; Neurosciences and Mental Health, Hospital for Sick Children, Toronto, ON, Canada; Psychology, University of Toronto, Toronto, ON, Canada; Hematology/ Oncology, Hospital for Sick Children, Toronto, ON, Canada; Diagnositic Imaging, Hospital for Sick Children, Toronto, ON, Canada; Cerebral Imaging Centre, Douglas Mental Health University Institute, Montreal, QC, Canada; Departments of Psychiatry and Biological and Biomedical Engineering, McGill University, Montreal, QC, Canada BACKGROUND: Cranial radiation therapy (CRT) is associated with declarative memory impairment and hippocampal volume loss in pediatric brain tumor survivors (PBTS). Animal studies suggest that this may reflect arrested neurogenesis in the dentate gyrus, the neurogenic region of the hippocampus. However, little is known about the distribution of CRT-induced volume loss across hippocampal subfields in humans and how this relates to memory. The goal of the present study was to characterize hippocampal subfield volume loss and relations to memory performance in PBTS. METHODS: MRI scans were obtained for 19 PBTS treated with CRT and 19 ageand sexmatched controls. An automated segmentationalgorithm wasused to segment hippocampi in each hemisphere into CA1, CA2/3, dentate gyrus (DG)/CA4, stratum radiatum/lacunosum/moleculare (SR/SL/SM) and subiculum. A subset of patients completed a paired associate verbal memory test from the Children’s or Wechsler’s Memory Scale (n 1⁄4 11). RESULTS: Global hippocampal volumes were reduced bilaterally in PBTS (p 1⁄4 0.002), but not all subfields differed significantly between groups. Bilateral DG/CA4 (p 1⁄4 0.049) and SR/SL/SM (p 1⁄4 0.019) were significantly smaller in patients. Diagnosis age in patients correlated with DG/CA4 (r 1⁄4 0.57) and SR/SL/SM (r 1⁄4 0.77) volumes, with younger diagnosis age predicting smaller volumes. Left DG/CA4 volume correlated with memory performance (r 1⁄4 0.72), with smaller volume predicting poorer performance. CONCLUSION: Hippocampal subfields are differentially vulnerable to CRT, with DG/CA4 and SR/SL/SM displaying particular compromise. Patients diagnosed at younger ages may be at the greatest risk for volume loss. The brain-behavior relationship that we observed suggests that DG/CA4 compromise may contribute to impaired memory in PBTS. Neuro-Oncology 18:iii145–iii158, 2016. doi:10.1093/neuonc/now081.58 #The Author(s) 2016. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.