Biocept, Inc. presented a study demonstrating the ability of its CNSide™ assay to identify HER2 and other actionable tumor alterations in the cerebrospinal fluid of patients with breast cancer and leptomeningeal disease (LMD). The poster was chosen for a Spotlight Presentation at the San Antonio Breast Cancer Symposium on Dec. 8, 2021. LMD is a devastating complication in which cancer spreads to the membrane surrounding the brain and spinal cord. The current standard of care for diagnosing LMD is through clinical evaluation, imaging and cytology, which have limited sensitivity and are unable to identify important tumor biomarkers such as HER2. HER2-targeted treatment for patients with breast cancer and LMD may provide substantial survival advantages over the expected median survival of less than three months. In this analysis, cerebrospinal fluid (CSF) of 63 patients with stage IV breast cancer and LMD was collected, and CSF tumor cells were captured and characterized using CNSide. HER2 amplification was detected in 56% of all patients. HER2 status differed between the primary tumor and LMD in 38% of cases, with more than 80% of those patients exhibiting a switch from a HER2-negative primary tumor to HER2-positive LMD.