Circulating Tumor Cells and Cell-free Tumor DNA in Evaluation and Management of Gliomas

Liquid biopsy (LB) is the real-time sampling of tumor cells or tumor nucleotides from biofluids such as serum and cerebrospinal fluid (CSF). In systemic malignancies, LB is established as a useful clinical tool, but its role in central nervous system (CNS) tumors is less clear. Gliomas are primary brain tumors that are generally incurable; the most common malignant brain tumor in adults is glioblastoma which carries a dismal prognosis. LB holds promise in the clinical care of gliomas, particularly as it could enable tumor assessment without requiring invasive tissue biopsy or reliance on imaging which is subject to misleading results. Circulating tumor cells (CTCs) are released from the primary tumor site into the circulation and cell-free tumor DNA (ctDNA) are fragments of tumor DNA released from the breakdown of tumor cells into the biofluids. Both have been explored as diagnostic, prognostic, and predictive tools in gliomas. This review explores the potential future clinical applications of LB in glioma and the limitations to the current research.