PATH-13. Methylation analysis in the diagnosis of pediatric CNS tumors; a single center experience

BACKGROUND: Tumors of Central Nervous System (CNS) comprise major cause of cancer-related morbidity and mortality during childhood. Recent advances in genome and epigenome research allow for molecular classification of CNS tumors, treatment stratification and therapeutic target identification. In many countries, including Greece, this integrated diagnosis is not possible, yet, in a routine setting due to financial and infrastructural reasons. DESIGN/METHODS: We analyzed the results from the methylation profiling performed on tumor samples from newly diagnosed and selected retrospective patients followed in our unit. Analyses were performed through the PTT2.0 and MNP2.0 Studies, as part of a collaboration project between ACCC (Athens Cancer Comprehensive Center) and DKFZ (German Cancer Research Center). RESULTS: Methylation arrays from 50 patients (mean age: 8years, range: 0-17years) have been analyzed. High calibrated score (>0.9) was achieved in 38 patients (76%) and in 33 (86%) of these, the histological diagnosis matched the methylation class. The remaining 5 cases, diagnosed by the local pathologist as ganglioneuroma, primitive neuroectodermal tumor, anaplastic astrocytoma, pineoblastoma and oligodendroglioma, were classified according to the methylation profiling as dermatofibrosarcoma protuberans, medulloblastoma group 3, high-grade glioma H3.3G34mutant, high-grade neuroepithelial tumor with BCOR alteration and glioneuronal tumor, respectively. Only four cases had no match in the classifier, while seven cases received low score (0.5-0.8). In 6 out of the 7 cases with low score, the diagnosis was confirmed with the use either of the copy-number profile inferred from the methylation array or by additional testing for gene fusions and mutations. In 25 medulloblastomas, methylation profiling provided molecular classification, according to the 2021 WHO Classification. CONCLUSIONS: Our experience on the first 50 cases suggests that methylation array needs to be considered as an integral part of the diagnostic process of pediatric patients with CNS tumors and highlights the importance of international collaboration programs in pediatric neuro-oncology.