Bridging the treatment gap in infant medulloblastoma: Molecularly informed outcomes of a globally feasible regimen.

BACKGROUND: Infant medulloblastoma represents an enormous challenge in neuro-oncology, due to their simultaneous high-risk of recurrence and high risk of severe neurodevelopmental sequelae with craniospinal irradiation. Currently infant medulloblastoma are treated with intensified protocols, either comprising intraventricular methotrexate or autologous transplant, both of which carry significant morbidity and are not feasible in the majority of the world. We sought to evaluate the molecular predictors of outcome in a cohort of infants homogeneously treated with induction chemotherapy, focal radiation and maintenance chemotherapy. METHODS: A retrospective analysis of twenty-nine young children treated with a craniospinal irradiation sparing strategy from Hospital Garrahan in Buenos Aires were profiled using Illumina HumanMethylationEPIC arrays, and correlated with survival. RESULTS: Twenty-nine children (range 0.3 - 4.6 years) were identified, comprising 17 SHH, 10 Group 3/4 and 2 non-medulloblastomas. Progression-free survival (PFS) across the entire cohort was 0.704 (95% CI 0.551-0.899). t-SNE analysis revealed three predominant groups, SHHβ, SHHγ and Group3. Survival by subtype was highly prognostic with SHHγ having an excellent 5-year PFS of 100% (95% CI 0.633-1) and SHHβ having a PFS of 0.56 (95% CI 0.42-1). Group 3 had a PFS of 0.50 (95% CI 0.25-1). Assessment of neurocognitive outcome was performed in 11 patients, the majority of survivors fell within the low average to mild intellectual disability, with a median IQ of 73.5. CONCLUSIONS: We report a globally feasible and effective strategy avoiding craniospinal radiation in the treatment of infant medulloblastoma, including a robust molecular correlation along with neurocognitive outcomes.