Tumor DNA from tumor in situ fluid was used to track genomic status and evolutionary models of gliomas under first-line treatment

Abstract Background: Tumor DNA from tumor in situ fluid (TISF) provides a minimally invasive approach to repeatedly interrogated the glioma genome and provides an opportunity to monitor the dynamics of pressure-induced cloning for recurrence and treatment selectivity. Understanding the evolution of glioma will be of great help in clinical and scientific research of glioma. Currently, no study has explored the recurrence process of glioma.Methods: We performed high-depth generation gene sequencing in multiple regions of matched primary and recurrent tumors. Using 60 primary tumor tissues and their TISF, 26 of whom had tumor recurrence and 6 underwent 2 surgeries, we analyzed the heterogeneity of each period.Results：We measured considerable genomic variation in glioma patients at different times under the stress of first-line treatment. In gliomas dominated by genomic alleles with low frequency (VAF < 1%), radiographic residues had higher VAF (p = 0.016), and patients with postoperative recurrence also had higher VAF (p < 0.0001). Under the pressure of treatment, polyclonal mutations gradually increased with tumor evolution, and high-frequency dominant clones gradually appeared. Samples of relapsed TISF contained more abundant clonal mutations. Sequencing of relapsed tumor tissue and relapsed TISF samples showed high consistency in mutation detection and estimation of allele frequency (p < 0.0001, VAF correlation, R2 = 0.8737). Heterogeneity at different stages of the tumor was shown in patients who were continuously monitored. We determined that TISF may detect elevated Tumor DNA variant allele fraction prior to positive imaging findings and effectively identify patients with pseudoprogression.Conclusions: Continuous TISF-DNA analysis reveals the evolutionary structure of gliomas under first-line therapy and can be used to track postoperative residual disease and tumor recurrence. Most importantly, it could move glioma research forward.