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

This study is a single-arm, prospective Phase I/II clinical trial, evaluating the safety, feasibility, and potential efficacy of combining Sacituzumab Govitecan with intrathecal pemetrexed chemotherapy for leptomeningeal metastases from HER2-negative breast cancer. The treatment regimen includes intravenous administration of Sacituzumab Govitecan (10 mg/kg) on Days 1 and 8 of each 21-day cycle, continuing until disease progression or unacceptable toxicity. Intrathecal pemetrexed chemotherapy is initiated on Day 2 via intracerebroventricular or lumbar puncture. The treatment is divided into three phases: induction therapy, 15 mg twice weekly for 2 weeks; consolidation therapy, once weekly for 4 weeks; maintenance therapy, once monthly for patients with an effective response until relapse or death. In the Phase I cohort, 3-6 patients were enrolled. If dose-limiting toxicity (DLT) occurred in ≥2 patients, the intrathecal dose of pemetrexed was reduced to 10 mg, and enrollment continued to ensure a total of 6 evaluable patients. If DLT recurred in ≥2 patients among the subsequently enrolled patients, the trial would be terminated. If DLT occurred in ≤1 patient, the trial would proceed to Phase II.