• Histologically or cytologically confirmed HER-2 positive breast cancer (immunohistochemistry indicates HER-2 3+ and/or fluorescence in situ hybridization indicates HER-2 gene amplification)

• Diagnosed with breast cancer with leptomeningeal metastasis based on cerebrospinal fluid cytology combined with central nervous system function and brain imaging findings

• The patient has an Ommaya reservoir implanted or is eligible for implantation

• KPS ≥ 30

• Adequate bone marrow and liver and kidney function reserves: absolute neutrophil count (ANC) ≥ 1.5 x 109/L, platelets ≥ 100 x 109/L, hemoglobin ≥ 90 g/L. International normalized ratio (INR) or prothrombin time (PT) ≤ 1.5 x ULN. Activated partial thromboplastin time (aPTT) ≤ 1.5 x ULN. Total serum bilirubin ≤ 1.5 x ULN (patients with Gilbert's syndrome can be enrolled if total bilirubin \< 3 x ULN). Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.5 x ULN; if the patient has liver metastasis, this criterion is AST and ALT ≤ 5 x ULN.

• Female, aged between 18 and 75 years old

• Left ventricular ejection fraction (LVEF) \> 50%

• Voluntary signing of informed consent form