BIOM-70. CSF TUMOR CELL (CSF-TC) DETECTION, QUANTIFICATION AND BIOMARKER ASSESSMENT HELPS IN CLINICAL MANAGEMENT OF BREAST CANCER AND NON-SMALL CELL LUNG CANCER PATIENTS HAVING LEPTOMENINGEAL DISEASE (FORESEE STUDY, NCT05414123)

Abstract Leptomeningeal metastases (LM) or the presence of cancer cells in the cerebrospinal fluid (CSF)/pia remains a challenging disease to diagnosis and treat. Current standard of care methods to diagnose or assess treatment response of LM (Clinical Evaluation, MRI and Cytology) have limited sensitivity and specificity and are poorly quantifiable. This creates challenges for physicians to manage LM or determine the best course of treatment. The FORESEE Study was a multi-center, prospective clinical trial evaluating a novel diagnostic platform, CNSide, that aimed to overcome these challenges. The FORESEE study enrolled patients with breast or non-Small Cell Lung Cancer (NSCLC) with suspicion of or confirmed LM. CNSide can detect and quantify tumor cells in the CSF from patients with breast cancer or NSCLC having a suspicious or confirmed LM. This platform also is able to identify actionable mutations in the CSF via Fluorescent In Situ Hybridization (FISH) and next-generation sequencing. The primary end point of the FORESEE study was clinical utility and the impact of CNSide on physician treatment decisions. Secondary endpoints included evaluating the clinical performance of CNSide vs. cytology in tumor cell detection (sensitivity, specificity, PPV and NPV). The study enrolled 40 patients (22 breast cancer and 18 NSCLC). Each patient underwent standard of care diagnostic evaluations at baseline and at three follow up timepoints through their treatment. CNSide aided clinical decision making in 93% (50/54) of the clinical decisions. At baseline 39 patients were assessed and confirmed a positive LM diagnosis in 15% (6/39), a negative LM diagnosis in 8% (3/39), progression in 15% (6/39), resolution in 15% (6/39) and no progression, or resolution in 36% (14/39) of the patients. CNSide informed the specific drug selected for treatment in 26% (10/39) patients at baseline and demonstrated clinical high utility. The FORESEE data is undergoing ongoing analysis; updated analysis will be presented at the meeting.