TOWARDS CLINICAL IMPLEMENTATION OF LIQUID BIOPSY ANALYSIS FOR PAEDIATRIC BRAIN TUMOUR PATIENTS - A PAN-EUROPEAN EFFORT FOR STANDARDIZATION

BACKGROUND Liquid biopsies (LBs) allow for analysis of tumour-derived molecules, such as cell-free DNA (cfDNA) and microRNAs (miRNAs), complementing cancer diagnostics, therapy monitoring, and minimal residual disease detection. While circulation-based LB has benefit for extracranial tumour entities, peripheral blood has not historically been a reliable source for diagnosis and disease-monitoring in brain tumours. For these tumours, cerebrospinal fluid (CSF) analysis is better suited for detection despite being a more invasive procedure. However, standardized protocols for sample collection and pre-analytical parameters for these LBs currently are limited. AIM We aim to establish an evidence-based gold standard protocol for cfDNA and miRNA analyses from CSF in paediatric brain tumour patients. In addition to higher compliance in trial-related CSF sampling, this initiative seeks to facilitate identification of clinically relevant indications and time-points for collection, thereby paving the way for well-informed, routine CSF molecular diagnostics. METHODS AND RESULTS We have initiated the Liquid Biopsy Working Group within the framework of the International Society of Paediatric Oncology Europe Brain Tumour Group (SIOPE-BTG). Available literature on LB in brain tumours was critically assessed regarding pre-analytical parameters, downstream analyses and LB assay performance. To directly evaluate confounding by pre-analytical factors, we experimentally compared the impact of CSF sampling sites, storage conditions, and different pre-processing protocols. cfDNA and miRNA yields, purity, and the fraction of tumour-derived material were selected as read-outs and correlated with tumour tissue information. To prepare for clinical translation, we consulted clinical paediatric brain tumour trial coordinators to identify major bottlenecks for CSF sampling in routine clinical practice. In addition, clinical practitioners and patient/ parent representatives have been consulted to comprehensively represent the perspectives and needs of all stakeholders. Together, results of this collaborative effort will be fundamental to the successful clinical integration of LBs to improve the future management of paediatric brain tumour patients.