MBCL-21. EARLY CHILDHOOD MEDULLOBLASTOMA: SUBGROUP-SPECIFIC SURVIVAL IN PATIENTS TREATED WITH SYSTEMIC CHEMOTHERAPY AND INTRAVENTRICULAR MTX TO AVOID CRANIOSPINAL RADIOTHERAPY

Abstract PURPOSE/METHODS Methylation-based tumor classification results were obtained from 86 patients younger than four years with medulloblastoma treated with systemic chemotherapy and intraventricular methotrexate to avoid craniospinal radiotherapy (CSI). 70 were HIT trial participants and 16 observational patients. Subgroup specific survival was analyzed. RESULTS Median follow-up was 8.3 years in the 61 patients alive at last follow-up. 33 patients presented with metastatic disease. Methylation profiling results were WNT (n=1), SHH_INF (n=43), Group 3 (GRP3; n=32) and Group 4 (GRP4; n=10). Of 39 patients with desmoplastic/nodular histology, 38 patients had SHH_INF, one GRP4 medulloblastoma. Survival differed significantly according to methylation subgroup (5y-PFS WNT: 0%, SHH_INF: 79%, GRP3: 31%, GRP4: 70%, p