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This research investigates the relationship between radiation doses to key brain structures and neurocognitive outcomes in children treated for medulloblastoma.

June 26, 2026Open Access

ID #1210 Associations Between Radiation Dose to Critical Brain Structures and Neurocognitive Outcomes in Patients Treated for Medulloblastoma on COG ACNS0331: A Report from the Children’s Oncology Group.

Key Points

This research investigates the relationship between radiation doses to key brain structures and neurocognitive outcomes in children treated for medulloblastoma.
Examined data from 128 medulloblastoma patients in ACNS0331 with neurocognitive testing and radiation plans.
Analyzed radiation doses to various CNS regions including the supratentorial brain and temporal lobes.
Compared radiation modalities: 3DCRT, IMRT/VMAT, and protons.
Estimated IQ decreased by 2.4 points for each 1 Gy increase in mean ST dose for ages 3-7 (p=0.01).
For LTL, the IQ decreased by 1.3 points with 1 Gy increase in ages 3-7 (p=0.01) and by 1 point in all ages (p=0.02).
Significant dose-dependent correlations observed between radiation and neurocognitive dysfunction.

Abstract

Abstract Background The COG study ACNS0331 randomized medulloblastoma patients to receive an involved field (IF) vs a whole posterior fossa (PF) boost following craniospinal irradiation (CSI) and children under 8 years of age were randomized to either standard dose CSI to 23.4Gy or a reduced dose CSI to 18Gy.Children aged 3+ participated in neuropsychological testing. Methods We identified 128 consecutive patients from ACNS0331 with both neurocognitive testing and complete radiation plan data.CNS regions including whole brain, supratentorial brain (ST), temporal lobes (TL), cerebellum, and brainstem were re-contoured in all patients for consistency. Results At T2 (2-3yrs post-dx), estimated IQ decreased by 2.4 points for every 1 Gy increase to the mean ST dose in pts ages 3-7 (p = 0.01), decreased by 1.3 points (ages 3-7) and 1 point (all ages) for every 1 Gy increase to the mean LTL dose (p = 0.01; p = 0.02), and decreased by 1 points for every 4% increase to LTL V30 and 3% increase to LTL V40 in pts of all ages (p = 0.04; p 0.01).RT dose to CNS structures was examined by modality (3DCRT vs IMRT/VMAT vs Protons). Patients receiving PF boost with 3DCRT had the highest mean ST/LTL doses (32Gy/44Gy) and those receiving IF boost and protons had the lowest mean ST/LTL doses (27Gy/30Gy).Mean LTL V50 was: PF + 3D (40%), PF+IMRT (25%), PF+protons (10%), IF + 3D (18%), IF+IMRT (15%), IF+protons (8%). Late Breaking Results T3 (5 year) timepoints have been updated and will be analyzed.Correlations between dose to Hippocampus, Corpus Callosum, Cochlea and neurocognitive outcomes will be presented, which were not included in the 2018 T2 analysis.Supratentorial and Temporal Lobe correlations will be updated.Critical structure dosimetry from proton cohort compared to photon cohort will be presented as well. Conclusions Relatively small increases in dose across sensitive CNS regions significantly increased the risk of neurocognitive dysfunction and radiation modality influenced structural doses significantly, independent of randomization.

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