Deformation heterogeneity radiomics to predict molecular subtypes of pediatric Medulloblastoma on routine MRI.

Medulloblastoma (MB) is the most common malignant brain tumor in children. Currently, "one-size-fits-all" radiation and chemotherapy treatment regimen is employed for treating MB patient, causing at least some children to undergo highly aggressive and in some cases, inadequate radiation therapy. Consequently, there is a need for prognostic and predictive tools for identifying disease aggressiveness and ultimately which patients with MB may be able to benefit from de-escalation of therapy. Genomic characterization of MB has recently identified 4 distinct molecular subgroups: Sonic Hedgehog (SHH), Wingless (WNT), Group 3, Group 4 each exhibiting different clinical behavior. The molecular sub-types have unique risk-profiles and outcomes, and patients could potentially benefit from sub-group specific treatments. However, the transition of these molecular MB subtypes into clinical practice has been limited due to challenges in availability of molecular profiling in most hospitals, as well as variability in clinical assessment. In this work, we present a radiomic feature that captures subtle tissue deformations caused due to the impact of tumor growth on the normal-appearing brain around tumor (BAT), to distinguish molecular sub-types of MB. First, we obtain voxel-wise deformation magnitude from the deformation orientations, after registering Gadolinium (Gd)-enhanced T1-w MRI scan for every study to a normal age-specific T1w MRI template. Deformation statistics are then computed within every 5mm annular BAT region, 0 < d < 60mm, where d is the distance from the tumor infiltrating edge, to capture subtle localized deformation changes around the tumor. Our results using multi-class comparison via one way ANOVA and post-hoc comparison showed significant differences across deformation magnitudes obtained for Group 3, Group 4, and SHH molecular sub-types, observed up to 15-mm outside the infiltrating edge. Our feasibility results suggest that the subtle deformation features in BAT observed on routine Gd-T1w MRI may potentially serve as surrogate markers to non-invasively characterize molecular sub-types of pediatric MB.