Keeping a track on leptomeningeal disease in non-small cell lung cancer: A single-institution experience with CNSide

Background: Leptomeningeal disease (LMD) is a devastating complication for patients with advanced cancer. Diagnosis and monitoring the response to therapy remains challenging due to limited sensitivity and specificity of standard-of-care (SOC) diagnostic modalities, including cerebrospinal fluid (CSF) cytology, MRI, and clinical evaluation. These hindrances contribute to the poor survival of LMD patients. CNSide is a CLIA-validated test that detects and characterizes CSF-derived tumor cells and cell-free (cf) DNA. We performed a retrospective analysis on the utility of CNSide to analyze CSF obtained from advanced non-small cell lung cancer (aNSCLC) patients with suspected LMD treated at the Huntsman Cancer Institute in Salt Lake City, UT. Methods: CNSide was used to evaluate CSF from 15 patients with aNSCLC. CSF tumor cell quantification was performed throughout treatment for 5 patients. CSF tumor cells and cfDNA were characterized for actionable mutations. Results: In LMD-positive patients, CNSide detected CSF tumor cells in 88% (22/25) samples versus 40% (10/25) for cytology (matched samples). CSF tumor cell numbers tracked response to therapy in 5 patients where CNSide was used to quantify tumor cells throughout treatment. In 75% (9/12) of the patients, genetic alterations were detected in CSF, with the majority representing gene mutations and amplifications with therapeutic potential. The median survival for LMD patients was 16.1 m (5.2-NR). Conclusions: We show that CNSide can supplement the management of LMD in conjunction with SOC methods for the diagnosis, monitoring response to therapy, and identifying actionable mutations unique to the CSF in patients with LMD.