BIOM-08. TARGETSELECTORTM CEREBROSPINAL FLUID (CSF) CIRCULATING TUMOR CELLS AND BIOMARKER ANALYSIS: IMPROVING SENSITIVITY AND TARGETED TREATMENT OPTIONS IN BREAST AND NSCLC CANCER PATIENTS WITH CNS INVOLVEMENT

Abstract

Abstract BACKGROUND Liquid biopsy has emerged as a minimally invasive and cost-effective strategy to assess cancer biomarkers without the risk of complications associated with biopsies. Once a tumor has metastasized to the brain, circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA) can be found in the cerebrospinal fluid (CSF). We analyzed CSF samples from patients(pts) with primary lung or breast cancer with either brain (BM) or leptomeningeal disease (LMD). Here we report the analytical and clinical validation of Target Selector™ CSF assays. METHODS CSF was collected prospectively from pts with a prior solid tumor diagnosis and confirmed or clinical/ radiological suspicion of BM or LMD. CTCs were captured in microfluidic channel and classified as either CK+ or CK-. Cell-free total nucleic acids (cfTNA) was extracted from CSF supernatant and underwent both Target Selector™ single gene and next-generation sequencing (NGS) NSCLC and breast multi-gene testing. For NGS, data analysis was performed using Torrent Suite with annotation and curation by Ion Reporter and Oncomine Knowledgebase Reporter software. RESULTS The Target Selector™ CTC platform assays performed on clinical samples (n = 89) resulted in clinical sensitivity = 80.0%, clinical specificity = 96.6%, positive predictive value (PPV) = 98%, negative predictive value (NPV) = 70.0% at a limit of detection of 2 CTCs. For molecular analyses, Target Selector™ platform assays resulted in clinical sensitivity = 85.2%, clinical specificity = 88.3%, PPV = 76.7%, and NPV = 93.0%. CONCLUSIONS Target Selector™ is a viable and sensitive platform for CTC detection and molecular analysis of CSF samples from patients with NSCLC or breast cancer with CNS metastases compared to the current standard of care (CSF cytology) and when imaging findings are equivocal. Identifying CTCs and actionable biomarkers can help to confirm CNS involvement when clinically suspected, guide targeted therapy selection and potentially monitor treatment response.