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Abstract:

Objective To investigate the feasibility of liquid biopsy in children with medulloblastoma through detecting circulating tumor DNA（ctDNA）in Cerebrospinal Fluid（CSF）. Methods Six patients diagnosed as medulloblastoma pre⁃operation by Magnetic Resonance Imaging（MRI）from Beijing Tiantan Hospital of Capital Medical University，and one patientreceived tumor dissemination from Beijing Shijitan Hospital of Capital Medical University were recruited in this prospective study between April 2019 and Dec 2019. CSF was collected by lumbar puncture 3~4 weeks after surgery. The tumor tissue and peripheral blood were collected at the same time. In order to acquire medulloblastoma associated alterations，the DNA sequencing was applied in tissue，blood and CSF of medulloblastoma cases based on next ⁃ generation sequencing（NGS）technology. Results The quality control of ctDNA extraction was unqualified in three cases. For the remaining 4 cases，the detection rate of ctDNA in CSF was 75%. Medulloblastoma related gene mutations such as KMT2D，KMT2C，TP53，NF1，PIK3CA，SMARCA4 and KMD5A were detected in CSF，but only KMT2D and SMARCA4 were detected in tumor tissues. Conclusion It is feasible to detect ctDNA in CSF in medulloblastoma. Furthermore，there were more detectable medulloblastoma⁃ related alterations in CSF than those in tumor tissue

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