IMG-30. DIFFUSE MIDLINE GLIOMA MAP TO A COMMON FUNCTIONAL NETWORK ASSOCIATED WITH TUMOUR PROGRESSION AND OVERALL SURVIVAL

Abstract

Abstract BACKGROUND Gliomas form bidirectional, functional synapses with otherwise healthy neurons: increasing neuronal excitability and driving tumour growth. The prognostic significance of this phenomenon does, however, remain unknown. METHODS This study used tumour location and tumour network mapping to identify brain networks associated with tumour progression and overall survival (OS) in 90 children with diffuse midline glioma, H3K27-altered (DMG). Tumours were segmented on volumetric magnetic resonance imaging and mapped to a standard template. Brain networks functionally connected to each tumour were computed using normative paediatric resting-state functional magnetic resonance imaging (n=525). RESULTS Median OS in the discovery cohort was 9.5 months (interquartile range 7.0-14.5 months). Comparison of tumour location in short-term (<18 months; n=75) and long-term (≥18 months; n=15) survivors of DMG identified an area of maximal anatomic overlap associated with short-term survival in the mid-pontine tegmentum and corticospinal tracts (89%; P<0.05). Tumour location was, however, not associated with OS (P=0.347). We, therefore, seeded tumour-to-brain resting-state functional connectivity maps from this a priori tegmental region-of-interest, identifying a specific brain network associated with short-term survival defined by functional connectivity to the medial prefrontal cortex, thalami, and cerebellum (P<0.0005). High and low tumour connectivity to this network was associated with short-term and long-term OS, respectively, using both univariate (P=0.013) and multivariate models controlling for treatment and tumour volume (P=0.016). Final, subset analysis of longitudinal neuroimaging in children within one month of death (n=21) showed tumour progression mapped to this same functional network and exhibited a dominant (left) hemispheric predominance (P<0.05), underpinned by increased tumour connectivity to the right (P=0.0270) rather than left (P=0.1802) corticospinal tract, and associated with OS (P=0.02). DISCUSSION We map DMG to a unified and prognostically important functional network, further establishing DMG as a circuit disorder. Interventions aiming to modulate this network may inform future treatment strategies for affected children.