MBCL-44. THE MOLECULAR AND CLINICAL LANDSCAPE OF INFANT MEDULLOBLASTOMA (iMB): RESULTS AND MOLECULAR ANALYSIS FROM A PROSPECTIVE, MULTICENTER PHASE II TRIAL (SJYC07)

Abstract BACKGROUND iMB has inferior survival to older children principally due to radiation-sparing therapy. To better understand which patients may benefit from radiation-sparing protocols, we describe the molecular landscape of iMB and report the iMB outcome on the SJYC07 trial designed to defer, reduce, or delay radiation exposure. METHODS We assembled a molecular cohort of 190 iMBs and a SJYC07 trial cohort of 81 iMBs. Tumors were sub-classified into molecular subgroups based on DNA methylation profiles and overlaid with mutations and copy-number alterations. PFS and OS for the SJYC07 cohort was estimated across clinical risk groups, consensus molecular subgroups, and in the context of novel MB subtypes. RESULTS Computational analysis of DNA methylation array data divided iMB into three of the four consensus subgroups: SHH, G3, and G4 (absent WNT). Clinical outcome of iMBSHH was superior to iMBGroup3/Group4 (5-year PFS: 51 ± 8% vs 11 ± 10%, P