Diagnostic value of circulating tumor cells in cerebrospinal fluid

OBJECTIVE: To assess circulating tumor cells in cerebrospinal fluid as a diagnostic approach to identify meningeal metastasis in patients with non-small cell lung cancer by using tumor marker immunostaining–fluorescence in situ hybridization (TM-iFISH). METHODS: In 5 non-small cell lung cancer patients who were confirmed to have developed meningeal metastasis by cerebrospinal fluid cytology, 20 ml of cerebrospinal fluid was obtained through lumbar puncture, from which 7.5 ml was utilized for TM-iFISH to identify and quantitate circulating tumor cells, 10ml for cerebrospinal fluid cytology, and 2.5ml for detection of cerebrospinal fluid tumor markers. RESULTS: TM-iFISH examination identified 18 to 1,823 circulating tumor cells per 7.5ml cerebrospinal fluid. In contrast, cytology assessment revealed tumor cells in only 2 cases. The expression levels of cerebrospinal fluid tumor markers were all increased in all 5 patients when compared with their respective serum levels. Contrast-enhanced MRI scans demonstrated presence of meningeal metastasis in all 5 cases. CONCLUSION: TM-iFISH may become a novel cerebrospinal fluid-based diagnostic strategy to identify circulating tumor cells and meningeal metastasis as compared to traditional diagnostic approaches, although its superior sensitivity and specificity needs to be confirmed through additional studies with a larger sample size.