Advancing Beyond the Hippocampus to Preserve Cognition for Patients with Brain Metastases: Dosimetric Results from a Phase 2 Trial of Memory-Avoidance Whole Brain Radiotherapy

Introduction: Recent advances to preserve neurocognitive function in patients treated for brain metastases include stereotactic radiosurgery (SRS), hippocampal avoidance whole radiation therapy (HA-WBRT), and memantine administration. The hippocampus, corpus callosum, fornix, amygdala are key substructures with a low propensity metastases. Herein, we report our preliminary experience using “memory-avoidance” WBRT (MA-WBRT) approach that spares these >15 metastases.MethodsTen consecutive MA-WBRT on phase 2 clinical trial were reviewed. In each patient, the hippocampi, amygdalae, fornix contoured. Patients not eligible if they had substructures. A memory- region created 5mm volumetric expansion around Hotspots avoided hypothalamus pituitary gland. Coverage of was prioritized over memory dose constraints. Dose constraints structures included D100% ≤ 9Gy D0.03cc 16Gy (variation acceptable 20Gy). LINAC-based modulated arc (VMAT) plans generated prescription 30 Gy 10 fractions.ResultsOn average, structure volume 37.1 ccs (Range: 25.2-44.6 ccs), occupying 2.5% entire target volume. All treatment met constraint, 8/10 priority given tumor coverage remaining cases. Target (D98% >25Gy) homogeneity (D2% 37.5Gy) achieved all plans.ConclusionsModern VMAT techniques allow sparing amygdala, good homogeneity. After enrollment is completed, quality life cognitive data will be evaluated assess efficacy mitigate declines cognition after radiation.