Prognostic significance of clinical, histopathological, and molecular characteristics of medulloblastomas in the prospective HIT2000 multicenter clinical trial cohort

Abstract

This study aimed to prospectively evaluate clinical, histopathological and molecular variables for outcome prediction in medulloblastoma patients. Patients from the HIT2000 cooperative clinical trial were prospectively enrolled based on the availability of sufficient tumor material and complete clinical information. This revealed a cohort of 184 patients (median age 7.6 years), which was randomly split at a 2:1 ratio into a training (n = 127), and a test (n = 57) dataset in order to build and test a risk score for this population. Independent validation was performed in a non-overlapping cohort (n = 83). All samples were subjected to thorough histopathological investigation, CTNNB1 mutation analysis, quantitative PCR, MLPA and FISH analyses for cytogenetic variables, and methylome analysis. By univariable analysis, clinical factors (M-stage), histopathological variables (large cell component, endothelial proliferation, synaptophysin pattern), and molecular features (chromosome 6q status, MYC amplification, subgrouping) were found to be prognostic. Molecular consensus subgrouping (WNT, SHH, Group 3, Group 4) was validated as an independent feature to stratify patients into different risk groups. When comparing methods for the identification of WNT-driven medulloblastoma, this study identified CTNNB1 sequencing and methylation profiling to most reliably identify these patients. After removing patients with particularly favorable (CTNNB1 mutation, extensive nodularity) or unfavorable (MYC amplification) markers, a risk score for the remaining “intermediate molecular risk” population dependent on age, M-stage, pattern of synaptophysin expression, and MYCN copy-number status was identified, with speckled synaptophysin expression indicating worse outcome. Test and independent validation of the score confirmed significant discrimination of patients by risk profile. Methylation subgrouping and CTNNB1 mutation status represent robust tools for the risk stratification of medulloblastoma. A simple clinico-pathological risk score was identified, which was confirmed in a test set and by independent clinical validation.Electronic supplementary materialThe online version of this article (doi:10.1007/s00401-014-1276-0) contains supplementary material, which is available to authorized users.

DNA methylation-based classification of central nervous system tumours

“…Areas with highest tumour cell content (≥70%) were selected for DNA extraction. Subsets of the reference cohort have been previously published 4,9–16,26–33 . Additional patient characteristics are given in Supplementary Table 2.…”

Risk stratification of childhood medulloblastoma in the molecular era: the current consensus

“…[5][45] The diagnosis of WNT tumors can be established by several methods, the most accurate being sequencing exon 3 of CTNNB1 , DNA methylation profiling or gene expression profiling. [39] A combination of both immunohistochemistry for nuclear beta-catenin and FISH or DNA copy number array profiling demonstrating monosomy 6 can also be used to reliably identify WNT tumors. [39] [11, 17]…”

Genetic and molecular alterations across medulloblastoma subgroups

“…The next generation of clinical trials is already taking subgroup into account to rationally stratify patients and tailor therapy. Accurate, robust, and inexpensive subgroup prediction methods are essential; molecular subgroups can be reliably assigned by either expression profiling or through the use of genome wide methylation arrays [13, 14]. Further investigation into the molecular genetics of medulloblastoma will hopefully pave the way for new targeted therapeutic strategies to cure this devastating childhood disease.…”

“…Less frequent is Gorlin syndrome which is an autosomal dominate disease characterised by mutations of the transmembrane receptor Patched1 ( PTCH1 ). The majority of these patients will acquire basal cell carcinoma, while about 5–20% will get medulloblastoma [13, 14]. Deletion of the PTCH1 locus results in higher Smoothened (SMO) activity and upregulation of the Sonic Hedgehog (Shh) signalling pathway, a marker of the SHH subgroup.…”