Circulating tumour DNA from the cerebrospinal fluid allows the characterisation and monitoring of medulloblastoma

Genètica del càncer; Càncer del SNC; Càncer pediàtricGenética del cáncer; Cáncer del SNC; Cáncer pediátricoCancer genetics; CNS cancer; Paediatric cancerThe molecular characterisation of medulloblastoma, the most common paediatric brain tumour, is crucial for the correct management and treatment of this heterogenous disease. However, insufficient tissue sample, the presence of tumour heterogeneity, or disseminated disease can challenge its diagnosis and monitoring. Here, we report that the cerebrospinal fluid (CSF) circulating tumour DNA (ctDNA) recapitulates the genomic alterations of the tumour and facilitates subgrouping and risk stratification, providing valuable information about diagnosis and prognosis. CSF ctDNA also characterises the intra-tumour genomic heterogeneity identifying small subclones. ctDNA is abundant in the CSF but barely present in plasma and longitudinal analysis of CSF ctDNA allows the study of minimal residual disease, genomic evolution and the characterisation of tumours at recurrence. Ultimately, CSF ctDNA analysis could facilitate the clinical management of medulloblastoma patients and help the design of tailored therapeutic strategies, increasing treatment efficacy while reducing excessive treatment to prevent long-term secondary effects.We would like to thank the patients at the Vall d’Hebron Hospital that were enrolled in the study and their families. The study was undertaken with the support of the Fundación Asociación Española contra el Cáncer (AECC), FERO (EDM), Ramón Areces Foundation, Cellex Foundation, BBVA (CAIMI), the ISCIII, FIS (PI16/01278) and the Juan de la Cierva fellowship (L.E). X.S.P. is supported by Ministerio de Economía y Competitividad (MINECO) SAF2013-45836-R and CIBERONC; A.D.N. is supported by the Department of Education of the Basque Government (grant number PRE_2017_1_0100). We thank CERCA Programme/Generalitat de Catalunya for institutional support