Detection of circulating hybrid cells and circulating tumor cells in cerebrospinal fluid for leptomeningeal metastasis diagnosis and therapeutic prediction.

Purpose: Leptomeningeal metastasis (LM) represents a serious complication of advanced malignancies with poor prognosis. Conventional diagnostic approaches, such as MRI and cerebrospinal fluid (CSF) cytology lack sufficient sensitivity-particularly in early-stage disease or when imaging modalities are inconclusive. This study explores the diagnostic utility of circulating tumor cells (CTCs) and circulating hybrid cells (CHCs) in CSF for LM detection. Methods: A cascaded filter deterministic lateral displacement microfluidic chip was utilized to enrich CTCs and CHCs from the CSF of 27 patients with LM and 22 individuals with non-neoplastic neurological conditions. Identification of CSF-derived CTCs and CHCs was based on immunofluorescence staining combined with characteristic neoplastic morphology. Results: The detection frequency and absolute counts of CTCs and CHCs were markedly elevated in LM patients compared to non-LM controls (p < 0.0001). A positive correlation was observed between CTC and CHC levels (rs = 0.8406, p < 0.0001). ROC analysis revealed robust diagnostic performance, with AUC values of 0.8727 for CTCs, 0.8600 for CHCs, and 0.9545 for CK-positive cells (a composite of CTCs and CHCs). Importantly, in two LM cases where MRI and cytology failed to provide diagnostic confirmation, CSF-CTC and CHC analyses successfully identified significant cell counts. Conclusion: CSF-CTCs and CHCs represent promising biomarkers for LM diagnosis and therapeutic prediction with high sensitivity and specificity, complementing traditional MRI and cytology diagnostic approaches. These findings highlight their potential clinical utility and underscore the need for further studies to explore CHC formation mechanisms and their implications in LM pathogenesis and treatment strategies.