The experience of using liquid biopsy in diffuse midline gliomas of the brain in children

Introduction. Diffuse midline gliomas (DMG) in children are among most severe diseases in neuro- oncology. Radical surgical treatment of these tumors is impossible, since they are located close to the nuclei of the cranial nerves and the pathways located in the brainstem. The development of cytological and molecular genetics has led to the understanding that the molecular biological characteristics of tumors are extremely important, since in the same histological picture, genetically different neoplasms have different prognosis and require different therapeutic approaches. The modern WHO classification of CNS tumors from 2021 is based not only on the histological structure of the neoplasm, but also on the molecular and biological characteristics of clinical significance. At the same time, the lack of morphological verification in children with DMG does not allow to expand and personalize therapy. Performing a liquid biopsy of cerebrospinal fluid and blood allows noninvasively examining the molecular profile of DMG, allowing to choose the optimal treatment protocol and predict the course of the process.The purpose of this work is to study the concentration of ctDNA K27M of the mutant and wild type H3F3A gene in the cerebrospinal fluid, their prognostic significance, and their dynamics in blood plasma in children with DMG before and during radiotherapy (RT).Patients and research methods. Patients with DMG were divided into the groups with or without disease progression according to CNS MRI data 3 months after completion of the RT course. With the help of digital drip PCR (ddPCR), the cerebrospinal fluid and peripheral blood of 157 patients with DMG were analyzed.Results. A significant increase in the concentration of mutant ctDNA and wild-type ctDNA of the H3F3A (K27M) gene in blood plasma was shown. An increase in the concentration of mutant ctDNA and wild-type ctDNA of the H3F3A (K27M) gene by the end of the RT course was typical for patientswith disease progression in the form of the appearance of metastatic foci in the central nervous system or continued tumor growth ( p function show_eabstract() { $('#eabstract1').hide(); $('#eabstract2').show(); $('#eabstract_expand').hide(); }