Circulating epithelial tumor cell analysis in CSF in patients with leptomeningeal metastases.

OBJECTIVE: The primary objective was to determine the sensitivity and specificity of epithelial cell adhesion molecule (EpCAM) immunoflow cytometry circulating tumor cells (CTC) analysis in CSF in patients with suspected leptomeningeal metastases (LM). The secondary objective was to explore the distribution of driver mutations in the primary tumor, plasma, cell free CSF (cfCSF), and isolated CTC from CSF in non-small cell lung cancer (NSCLC). METHODS: We tested the performance of the CTC assay vs CSF cytology in a prospective study in 81 patients with a clinical suspicion of LM but a nonconfirmatory MRI. In an NSCLC subcohort, we analyzed circulating tumor (ct)DNA of the selected driver mutations by digital droplet PCR (ddPCR). RESULTS: The sensitivity of the CTC assay was 94% (95% confidence interval [CI] 80-99) and the specificity was 100% (95% CI 91-100) at the optimal cutoff of 0.9 CTC/mL. The sensitivity of cytology was 76% (95% CI 58-89). Twelve of the 23 patients with NSCLC had mutated epidermal growth factor receptor (EGFR). All 5 tested patients with LM demonstrated the primary EGFR driver mutation in cfCSF. The driver mutation could also be detected in CTC isolated from CSF. CONCLUSION: CTC in CSF are detected with a high sensitivity for the diagnosis of LM. ddPCR can determine EGFR mutations in both cfCSF and isolated CTC from CSF of patients with EGFR-mutated NSCLC and LM. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that EpCAM-based immunoflow cytometry analysis of CSF accurately identifies patients with LM.

Integration of rare cell capture technology into cytologic evaluation of cerebrospinal fluid specimens from patients with solid tumors and suspected leptomeningeal metastasis.

INTRODUCTION: Dissemination of tumor to the leptomeninges, subarachnoid space, and cerebrospinal fluid (CSF) is termed leptomeningeal metastasis (LM) and occurs in approximately 5% of patients with solid tumors. LM is associated with dismal clinical prognosis, and routine cytologic and radiologic methods for diagnosing LM have limited sensitivity. The CellSearch immunomagnetic rare cell capture assay is FDA-approved to detect circulating tumor cells (CTCs) in peripheral blood, but whether it may have a role in identifying CSF CTCs is still unclear. MATERIAL AND METHODS: CSF specimens from 20 patients with clinically suspected solid tumor LM collected from 2 institutions between October 2016 and January 2019 were evaluated with routine CSF cytology and underwent concurrent CTC testing with the CellSearch assay (Menarini-Silicon Biosystems, Huntingdon Valley, PA). The results of CTC testing were compared to routine CSF cytology and radiologic studies for detecting LM. RESULTS: The CellSearch assay achieved a sensitivity of 88.9% and specificity of 100% for detecting LM (using a threshold of 1 CTC/mL of CSF as the definition of a positive CTC result). One patient with negative CSF cytology but positive CTCs developed positive cytology 37 days later. CONCLUSIONS: In this proof-of-principle pilot study, we demonstrate that the CellSearch assay can be successfully integrated with the routine CSF cytologic workflow to aid in the diagnosis of solid tumor LM. Importantly, CTCs detected by this rare cell capture assay are found in a subset of patients with non-positive routine CSF cytology, which may have significant implications for patient management.

Encephalitis and GABAB receptor antibodies: novel findings in a new case series of 20 patients.

OBJECTIVE: To report the clinical features of 20 newly diagnosed patients with GABAB receptor (GABABR) antibodies and determine the frequency of associated tumors and concurrent neuronal autoantibodies. METHODS: Clinical data were retrospectively obtained and evaluated. Serum and CSF samples were examined for additional antibodies using methods previously reported. RESULTS: Seventeen patients presented with seizures, memory loss, and confusion, compatible with limbic encephalitis (LE), one patient presented with ataxia, one patient presented with status epilepticus, and one patient presented with opsoclonus-myoclonus syndrome (OMS). Nineteen (95%) patients eventually developed LE during the course of the disease. Small-cell lung cancer (SCLC) was identified in 10 (50%) patients, all with LE. Treatment and outcome was available from 19 patients: 15 showed complete (n = 7) or partial (n = 8) neurologic improvement after steroids, IV immunoglobulins, or plasma exchange and oncologic treatment when indicated; 1 patient died of tumor progression shortly after the first cycle of immunotherapy, and 3 were not treated. Five patients with SCLC had additional onconeuronal antibodies (Ri, amphiphysin, or SOX1), and 2 without tumor had GAD65 and NMDAR antibodies, respectively. GABABR antibodies were not detected in serum of 116 patients with SCLC without neurologic symptoms. CONCLUSION: Our study confirms GABABR as an autoantigen of paraneoplastic and nonparaneoplastic LE and expands the phenotype of GABABR antibodies to ataxia, OMS, and status epilepticus. The long-term prognosis is dictated by the presence of a tumor. Recognition of syndromes associated with GABABR antibodies is important because they usually respond to treatment.