HGG-59. Pediatric high-grade gliomas and the WHO classification on CNS Tumors - Different perspectives of pediatric neuro-oncologists and neuropathologists in the light of recent updates

Abstract

Abstract BACKGROUND: The WHO Classification of Tumors of the Central Nervous System has undergone major restructuring following rapid advances in brain tumor genomics and epigenomics. The most significant changes resulted from the introduction of molecularly defined diagnostic criteria in 2016 (revised 4th edition). In 2021 (5th edition), further essential molecular criteria were incorporated. In the present study, we sought to investigate potential differences between specialists in perception of these newly defined molecular subtypes of pediatric high-grade gliomas (pedHGG). METHODS: We designed a 22-question survey studying the impact of the revised 4th edition of the WHO classification on pedHGG. Data were collected and statistically analyzed to capture the spectrum of viewpoints and possible differences among neuro-oncologists and neuropathologists. RESULTS: 465 participants from 53 countries responded, of which 187 pediatric neuro-oncologists (40%), 160 neuropathologists (34%) and 118 experts in other related fields (neurosurgeons, radiotherapists, neuroradiologists and others; 26%). Neuro-oncologists reported having issues with the introduction of new molecular entities, such as the abolishment and renaming of established tumor entities. Neuropathologists did not define these problems to the same extent. However, both groups felt that in the 2016 version, less relevant or insufficient diagnostic definitions were available for pedHGG. Within the 2021 WHO classification, a substantial improvement was perceived regarding the definition of pedHGG entities. However, some issues of high clinical relevance, like the definition of clinical phenotypes such as diffuse intrinsic pontine glioma (DIPG) and gliomatosis cerebri, are yet to be addressed. CONCLUSIONS: Within the WHO classification of pediatric brain tumors, such as high-grade gliomas, rapid changes in nomenclature have been introduced because of substantial improvement in molecular characterization. This study highlights that ongoing cross-talk between advancing classification of pedHGG subtypes and its biological relevance and clinical impact is essential.