QOL-20. IMPACT OF RADIATION DOSE AND VOLUME ON MEMORY FUNCTIONING IN CHILDREN WITH MEDULLOBLASTOMA: A REPORT FROM CHILDREN’S ONCOLOGY GROUP (COG) ACNS0331

BACKGROUND/OBJECTIVES We examined longitudinal verbal and visual memory functioning in children treated for medulloblastoma on COG protocol ACNS0331. METHODS Children with medulloblastoma participated in neuropsychological testing at three timepoints over a 6-year period. Children aged 3–7 years were randomized to receive craniospinal irradiation (CSI) of either 23.4Gy (standard dose; SDCSI) or 18Gy (lower dose; LDCSI). Children aged 8+ received SDCSI. All children were also randomized to receive either a reduced radiation boost to the involved field (IFRT) or a standard boost to the whole posterior fossa (PFRT). Memory functioning was evaluated an average of 0.67(T1), 2.95(T2), and 4.90(T3) years post-diagnosis. RESULTS Of 464 eligible patients enrolled on ACNS0331, 354 (76%; 65.3% male, 83.1% white) completed some neuropsychological testing. Mean age at diagnosis was 9.1 years (range=3–19). Verbal and visual short-term memory and learning were broadly within the average range for the overall sample at all three timepoints. However, a large percentage of children exhibited scores ≥1SD below the mean on tasks of verbal learning both immediately (43.4%) and after a delay (40.7%) at T3. In addition, 58.6% of children randomized to SDCSI exhibited impairment in verbal learning after a delay compared to 34.8% of children randomized to LDSCI, and 35.0% of those aged ≥8 at diagnosis receiving SDCSI. CONCLUSIONS Younger children receiving SDCSI have particularly high rates of memory impairment five years after diagnosis of medulloblastoma. Limiting CSI dose and/or volume in young children treated for this diagnosis may improve outcomes for memory functioning.