BIOM-61. DETECTION OF HUMAN BRAIN CANCERS USING GENOMIC AND IMMUNE CELL CHARACTERIZATION OF CEREBROSPINAL FLUID THROUGH CSF-BAM

Abstract Patients who have radiographically detectable lesions in their brain or other symptoms compatible with brain tumors pose challenges for diagnosis. The only definitive way to diagnose such patients is through brain biopsy, an obviously invasive and dangerous procedure. Here we present a new workflow termed “CSF-BAM” that simultaneously identifies B cell or T cell receptor rearrangements, Aneuploidy, and Mutations using PCR-mediated amplification of both strands of the DNA from CSF samples. We first describe the details of the molecular genetic assessments and then establish thresholds for positivity using training sets of libraries from patients with or without cancer. We then applied CSF-BAM to an independent set of 209 DNA samples from patients with common, aggressive cancer types as well as other forms of brain cancers. Among the 129 samples from patients with the most common aggressive cancer types (high grade gliomas, medulloblastomas, or metastatic cancers to the brain), the sensitivity of detection was 81%. None of 30 CSF-BAM assays (100% specificity, 90% to 100% credible interval) were positive in CSF samples from patients without brain cancers. The sensitivity of CSF-BAM was considerably higher than that achieved with cytology. CSF-BAM provides an integrated multi-analyte approach to identify neoplasia in the central nervous system, provides information about the immune environment in patients with or without cancer, and has the potential to inform the subsequent management of such patients.