MBCL-37. CHEMOTHERAPY STRATEGIES FOR YOUNG CHILDREN NEWLY DIAGNOSED WITH CLASSIC (CLMB) OR ANAPLASTIC/LARGE CELL (A/LCMB) MEDULLOBLASTOMA UP TO THE ERA OF MOLECULAR PROFILING – A COMPARATIVE OUTCOMES ANALYSIS

BACKGROUND/OBJECTIVE: The introduction of German regimens, supplementing “standard” chemotherapy with both intravenous high-dose (HD-MTX) and intraventricular (IVENT-MTX) methotrexate, and North American regimens incorporating marrow-ablative chemotherapy with autologous hematopoietic cell rescue (HDCx+AuHCR), report encouraging outcomes for young children with medulloblastoma. We performed a comparative outcomes analysis of treatment strategies for young children with ClMB or A/LCMB. DESIGN/ METHODS: Data from 12 prospective multi-center trials published between 2005 and 2019 for children <six-years-old with ClMB or A/LCMB were reviewed; survivals were compared. RESULTS: COG-9921, UKCCSG-CNS9204, COG-P9934 and SJYCO7 employing standard chemotherapy with either no or risk-based irradiation, reported 3-5-year event-free survival (EFS) of 17+/-5%, 33+/-28% (ClMB), 14+/-7% and 13.8+/-9% (ClMB) respectively, with reported EFS of 0% for A/LCMB in UKCCSG-CNS9204 and SJYCO7. HIT-SKK’87, HIT-SKK’92 and HIT-SKK’00 incorporating HD-MTX and IVENT-MTX reported 2-10-year EFS of 30–34+/-10–11% for ClMB and 33+/-27% (HIT-SSK’00) for A/LCMB. Head Start HS-I-II combined, CCG-99703 and HS-III employing induction chemotherapy, with or without HD-MTX, followed by single or tandem HDCx+AuHCR reported 3-5-year EFS of 42+/-14%, 50+/-11% and 27+/-6% for ClMB, with EFS for A/LCMB of 38+/-13% (HS-III). Finally, 5-year overall survivals for ACNS0334, without or with induction HD-MTX, are 39% and 69% respectively for ClMB and A/LCMB combined. CONCLUSIONS: A trend towards better outcomes for young children with ClMB and A/LCMB is observed in trials including either HD-MTX and IVENT-MTX or including HD-MTX-containing induction chemotherapy and HDCx+AuHCR. Trials excluding HD-MTX, IVENT-MTX and HDCx+AuHCR have poorer outcomes.