Circulating Tumor DNA in Cerebrospinal Fluid as an Early Biomarker of Leptomeningeal Metastasis (LM)

The contents of dead/dying tumor cells can be detected in the bloodstream, and this may be
enhanced by the leaky vasculature of solid tumors. Circulating tumor DNA has been detected in
plasma from patients with osteosarcoma, breast cancer, and colorectal cancer, and in
cerebrospinal fluid from patients with cancer-associated neoplastic meningitis. Until
recently, it was impractical to develop an assay to routinely quantify circulating tumor DNA
due to heterogeneity between patients and tumors. Advances in genomic technology now permit
sequencing a tumor genome to identify patient-specific genomic aberrations. Major genomic
alterations (i.e., insertions, amplifications, deletions, inversions, translocations) can be
readily detected using PCR primers and probes which will recognize tumor DNA but not normal
DNA, permitting creation of a personalized assay to quantify tumor DNA levels in bodily
fluids. We therefore propose a pilot study to determine whether circulating tumor DNA levels
increase in CSF prior to cytological evidence of LM in patients with a history of cancer
originating from a visceral organ.

Inclusion Criteria:

1. Patient must have a previously diagnosed solid tumor malignancy originating from a
visceral organ (i.e., outside of the CNS), and present with signs and/or symptoms
consistent with carcinomatous meningitis (headache, vision dysfunction, hearing loss,
cranial nerve deficit, cognitive dysfunction, focal weakness or numbness suggestive of
cranial neuropathy or radiculopathy, cauda equine syndrome, meningismus, and/or bowel
or bladder dysfunction).

2. Age ≥ 18 years.

3. Patients will meet accepted standard of care and follow FDA guidance for low molecular
weight heparin use prior to lumbar puncture, specifically INR < 1.4 and PT within
normal range for DHMC laboratory, and platelet count >50,000. For enoxaparin use,
delay of Lumbar puncture to allow at least 12 hours after administration of
prophylactic doses, such as those used for prevention of deep vein thrombosis. Longer
delays (24 hours) are appropriate to consider for patients receiving higher
therapeutic doses of enoxaparin (1 mg/kg twice daily or 1.5 mg/kg once daily). A
postprocedure dose of enoxaparin should usually be given no sooner than 4 hours after
lumbar puncture. Aspirin and other antiplatelet therapy is permitted without timing
constraints prior to or after lumbar puncture.

4. Patient must consent to provide up to additional CSF (10 mL) and blood (10 mL) when
these fluids are drawn as part of clinically indicated procedures.

5. Patient must consent to permit genetic analysis of their cancer.

6. Patient capable of giving informed consent.

7. MRI of clinically symptomatic area (spine and/or brain) and/or head CT within the last
3 months to exclude brain disease that would contraindicate lumbar puncture.

Exclusion Criteria:

1. Evidence of a CNS mass creating mass‐effect or midline shift such that lumbar puncture
is contraindicated.

2. Previous or current hematological malignancy.

3. Previous or current primary CNS malignancy.

4. Prior treatment for CNS metastasis.

5. Known CNS autoimmune or inflammatory disease (i.e., Multiple Sclerosis,
neurosarcoidosis, chronic fungal, rickettsial or bacterial meningitis).

6. Patient is currently receiving treatment for LM.

7. Patient was previously diagnosed with LM.