• Age ≥ 18 years and ≤ 70 years, with no gender restrictions;

• ECOG performance score of 0 to 2;

• Expected survival ≥ 3 months;

• Patients with unresectable locally advanced, recurrent or metastatic triple-negative breast cancer who have failed treatment with taxane drugs are included.

• Ten tissue pathology slides of the primary lesion and/or metastatic lesion (preferably metastatic lesion) can be obtained before the start of treatment for exploratory analysis of molecular indicators related to therapeutic efficacy.

• Patients must have brain metastases confirmed by MRI, with at least one brain metastasis lesion that previously has not received radiotherapy and has a longest diameter of ≥ 1.0 cm; for brain metastasis lesions that have received local treatment, progression must be confirmed by imaging examination;

• Cohort A: Patients with brain metastases who have not received central nervous system radiotherapy before. Patients with new brain lesions after craniotomy are allowed to be included, provided that they have not received radiotherapy after surgery and at least 2 weeks have passed since the surgery;

• Cohort B: Patients with lesion progression or new lesions after whole brain radiotherapy (WBRT) or stereotactic radiotherapy (SRT). If a patient has multiple central nervous system lesions and only one or a few of them have received SRT treatment, and there are untreated lesions, such patients are still eligible for inclusion in this study;

• The use of mannitol or hormones for treatment is allowed before enrollment, but the hormone treatment dose should be stable for at least one week without the need for an increase;

⁃ All patients enrolled are required to have adequate hematologic, hepatic, and renal function;

⁃ Be able to understand the study procedures and sign informed consent.