Liquid Biopsy and Primary Brain Tumors

SIMPLE SUMMARY: Despite a substantial increase in publications in recent years, liquid biopsy from blood, cerebrospinal fluid (CSF), and other body fluids is usually not routinely used in cancer diagnostics and tumor monitoring. In this regard, brain tumors represent an additionally challenging group of tumors due to the blood–brain barrier as a potential suppressor of migrating tumor cells and their property of rarely metastasizing via the blood. Surprisingly, however, circulating tumor cells (CTCs) have been found in 20% of glioblastoma patients, which may allow for monitoring of tumor progression and response to therapies based on the genetic profiling of such tumors. Genetic biomarkers from CTC, circulating tumor DNA (ctDNA), extracellular vesicles, and microRNA (miRNA) are discussed. Here, we review the recent developments and future potential of liquid biopsy in brain tumors. ABSTRACT: Two decades of “promising results” in liquid biopsy have led to both continuing disappointment and hope that the new era of minimally invasive, personalized analysis can be applied for better diagnosis, prognosis, monitoring, and therapy of cancer. Here, we briefly highlight the promises, developments, and challenges related to liquid biopsy of brain tumors, including circulating tumor cells, cell-free nucleic acids, extracellular vesicles, and miRNA; we further discuss the urgent need to establish suitable biomarkers and the right standards to improve modern clinical management of brain tumor patients with the use of liquid biopsy.