Cerebrospinal fluid (CSF) represents a promising source of
cell-free DNA (
cfDNA) for
tumors of the central nervous system. A CSF-based liquid biopsy may obviate the need for riskier tissue biopsies and serve as a means for monitoring
tumor recurrence or response to
therapy. Spinal
ependymomas most commonly occur in adults, and aggressive resection must be delicately balanced with the risk of injury to adjacent normal tissue. In patients with subtotal resection, recurrence commonly occurs. A CSF-based liquid biopsy matched to the patient's spinal
ependymoma mutation profile has potential to be more sensitive then surveillance MRI, but the utility has not been well characterized for
tumors of the spinal cord. In this study, we collected matched blood,
tumor, and CSF samples from three adult patients with WHO grade II intramedullary spinal
ependymoma. We performed whole exome sequencing on matched
tumor and normal
DNA to design Droplet Digital™ PCR (ddPCR) probes for
tumor and wild-type mutations. We then interrogated CSF samples for
tumor-derived
cfDNA by performing ddPCR on extracted
cfDNA.
Tumor cfDNA was not reliably detected in the CSF of our cohort. Anatomic sequestration and low grade of intramedullary
spinal cord tumors likely limits the role of CSF liquid biopsy.