BIOM-04. CORRELATIVE PERFORMANCE OF CEREBROSPINAL FLUID (CSF) CIRCULATING TUMOR CELLS (CTC) AND CELL-FREE TUMOR-DERIVED DNA (CTDNA) IN LEPTOMENINGEAL METASTASES (LM) AND PARENCHYMAL BRAIN METASTASES (BM)

Abstract BACKGROUND CSF-CTC analysis through the CellSearch® platform has been studied as a diagnostic and prognostic tool for LM from solid tumors. CSF-ctDNA can be detected in and/or BM, with unclear significance. We aimed to evaluate CSF-CTCs predictors of diagnosis survival BM. METHODS retrospectively reviewed charts patients tumors who underwent ctDNA evaluation same lumbar puncture between 2016-2021 at Memorial Sloan Kettering Cancer Center. was diagnosed by MRI CSF cytology; considered “positive” if next-generation sequencing (NGS) ≥ 1 mutations using clinically validated thresholds. Associations newly were performed logistic regression, development cause-specific competing risks models. Survival analyses Cox proportional hazards modeling date first collection, adjusted time-dependent variable. RESULTS Out 151 total patients, 99 had time (58/99 LM, within 30 days collection), 52 BM only, which 8/52 (15%) developed later (median LM=235 days, range 57-364). predictive (OR=1.006, 95% CI:1.002-1.01, p=0.002 continuous CSF-CTCs; OR=3.60, CI:1.65-7.87, p=0.001 positive CSF-ctDNA). In small cohort without almost statistically significant predicting (HR=4.14, CI: 0.98-17.57, p=0.054) while not (HR=1.02, 0.99-1.04, p=0.21). all both (OR=1.004, 1.001-1.006, p=0.002) (OR=2.49, 1.51-4.15, p=0.0004) predicted survival. CONCLUSION could predict Presence CTCs associated poor central nervous system metastases.