Multimodal Treatment in Severe Breast Cancer Leptomeningeal Metastasis: A Rare Case of Prolonged Clinical Benefit

We report the case of a 44-year-old woman with previously treated hormone receptor-positive (HRpositive), human epidermal growth factor receptor 2 (HER2)-negative breast cancer who developed a late metastatic recurrence with extensive leptomeningeal metastasis (LM), intracranial hypertension, and symptomatic hydrocephalus.Rapid neurological deterioration resulted in an Eastern Cooperative Oncology Group performance status (ECOG PS) of 4. Placement of a programmable ventriculoperitoneal shunt controlled hydrocephalus and resulted in marked neurological and functional recovery to ECOG PS 1, enabling treatment with intrathecal methotrexate and systemic letrozole and ribociclib.An ovarian metastasis identified during systemic staging was subsequently resected.Treatment was associated with a reduction in malignant cells in the cerebrospinal fluid (CSF), normalization of serum tumor markers, and sustained extracranial disease control.Intrathecal methotrexate was discontinued following the development of radiological leukoencephalopathy and persistent/progressive spinal leptomeningeal involvement.Despite persistent radiological and cytological evidence of LM, the patient remains clinically stable, functionally independent, and professionally active, with an ECOG-PS of 1 and sustained extracranial disease control, 15 months after LM diagnosis.This case highlights the potential for prolonged clinical benefit from an individualized multimodal strategy in severe breast cancer LM.Effective management of hydrocephalus was critical in restoring performance status and enabling subsequent intrathecal and systemic treatment.