Medulloblastoma in adults: Cytogenetic phenotypes identify prognostic subgroups

Medulloblastoma (MB) is a rare disease in adults. In this study we elucidated the genetic landscape and prognostic impact of genetic aberrations in a cohort of 117 adult medulloblastomas. Histological features and pathway activation were evaluated on the protein level; 14.5% showed WNT activation, 63.3% SHH activation and 22.2% were annotated to non-WNT/non-SHH-MB. Genome-wide copy number analysis was performed by molecular inversion probe array technology. MB-related genes were sequenced in WNT- and SHH-activated MBs. 79.7% of SHH-MBs showed desmoplastic/nodular, all other MBs classic histology. WNT-MBs carried oncogenic CTNNB1 mutations in 88.2% and had monosomy 6 in 52.9%. In SHH-MBs, TERT promoter mutations occurred in 97%, mutations in PTCH1 in 38.2%, SMO in 15.5%, SUFU in 7.4%, and TP53-mutations in 4.1%. 84.6% of non-WNT/non-SHH-MBs had an isochromosome 17q. A whole chromosomal aberration (WCA) signature was present in 45.1% of SHH-TP53wt-MBs and 65.4% of non-WNT/non-SHH-MBs. In 98 cases with survival data, WNT-MBs had a 5-year overall survival (OS) of 68.6%. SHH-MBs TP53-wild-type and non-WNT/non-SHH-MBs showed 5-year OS of 80.4% and 70.8%, respectively. TP53-mutant SHH-MBs represented a prognostically unfavorable entity; all patients died within 5 years. Patients with a WCA signature showed significantly increased OS (p-=-0.011 for SHH-TP53wt-MBs, p-=-0.048 for non-WNT/non-SHH-MBs). Bisulphite converted FFPE-DNA from 27 samples were hybridised to the Illumina Infinium MethylationEPIC BeadChip (850K)