Tumor In Situ Fluid Was Used to Characterize Glioma in Real-Time to Monitor Minimal Residual Disease and Tumor DNA Relapse

Background: Glioma is highly heterogeneous. Real-time tumor markers in vivo can most truly reflect the clonal evolution of glioma, and can accurately monitor postoperative minimal residual disease (MRD) and early tumor DNA relapse. The histological and molecular markers of resected tumor could not represent the characteristics of recurrent tumor, and the reference basis of postoperative clinical treatment plan should be adjusted. Methods: This retrospective cohort analyzed 32 patients with glioma from January 1, 2018 to January 31, 2020. Samples of tumor tissue, tumor fluid in situ and cerebrospinal fluid were collected, and next-generation tumor DNA sequencing was performed. Findings: Adequate tumor DNA was detected in TISF. The consensus rate of shared mutations at tumor progression was 45.8%, the variant allele fractions (VAFs) for TISF mutations were between 0.1% and 84.3%. VAF and cfDNA concentrations increased as the tumor progressed. At tumor progression, 100% (15/15) of tumor DNA was positive in TISF, CSF-ctDNA was detected in only 4 patients (26.7%, 4/15). The concentration of cfDNA in TISF samples ranged from 0.9-346.5ng/ mL, while that in CSF was only 0.55-16.23ng/mL. The level of shared mutation VAF was higher than that of CSF in TISF. High concentration of cfDNA in early postoperative TISF indicates high residual disease in early postoperative TISF, which is an early recurrence risk ( 600 days Patients (p = 0.006). Interpretation: Tumor DNA derived from TISF can find the molecular information of MRD before tumor recurrence, which cannot be detected by imaging and CSF-ctDNA. It can provide accurate glioma genomic information in real-time in vivo, and can monitor tumor MRD, clonal evolution, early tumor DNA relapse, and provide clinical treatment strategies. Funding Statement: Science and Technology Tackle Program of Henan Province and Joint Project of Medical Science and Technology Tackling Plan of Henan Province (Grants no. 192102310126 and 201601016) Declaration of Interests: Authors declare that they have no competing interest. Ethics Approval Statement: Approval was obtained from the Ethics Committee and Institutional Review Committee of the People’s Hospital of Henan Province.