Sacituzumab Govitecan and Intrathecal Chemotherapy for Treating Leptomeningeal Metastases From Her2-negative Breast Cancer

This trial tests sacituzumab govitecan (a targeted chemotherapy drug) combined with chemotherapy injected directly into the spinal fluid to treat leptomeningeal metastases — cancer that has spread to the fluid and membranes surrounding the brain and spinal cord — in patients with HER2-negative breast cancer. **You may be eligible if...** - You are 18 or older with confirmed HER2-negative breast cancer (IHC 0, 1+, or 2+/ISH-negative) - Cancer cells have been found in your spinal fluid (CSF), or imaging and symptoms strongly suggest leptomeningeal spread - Your major organ function is adequate **You may NOT be eligible if...** - You have poor blood counts (low white cells, platelets, or hemoglobin) - You have significant liver dysfunction - You are HIV-positive or have serious immune deficiency - You are pregnant or breastfeeding - You are unwilling to use contraception if of childbearing potential Talk to your doctor to see if this trial is right for you.