Evaluating the Efficacy and Safety of PD-L1 Monoclonal Antibody Combined With VEX Metronomic Chemotherapy and Concurrent or Delayed Radiotherapy in Patients With Advanced HER2-Negative Breast Cancer With Brain Metastasis

Exclusion criteria

• . The subject has leptomeningeal metastasis.
• . If the patient has concurrent brain metastasis, the neurological symptoms are too severe to cooperate with radiotherapy.
• . Malabsorption syndrome, or the disease significantly affects gastrointestinal function; or after subtotal gastrectomy, or after proximal small bowel resection, which may affect the absorption of oral metronomic chemotherapy agents.
• . The subject has dysphagia or is unable to swallow tablets.
• . Known history of another invasive malignancy that is progressing or requires active treatment within the past 5 years. (Subjects with a history of cutaneous basal cell carcinoma, squamous cell carcinoma of the skin, ductal carcinoma in situ of the breast treated with curative intent, or in situ cervical cancer are not excluded.)
• . Previous treatment with anti-PD-1, anti-PD-L1, or anti-PD-L2 agents, or targeted drugs acting on another stimulatory or co-inhibitory T-cell receptor (e.g., CTLA-4, OX40, CD137).
• . Diagnosis of immunodeficiency or receiving long-term systemic corticosteroid therapy (daily dose exceeding 10 mg prednisone equivalent) or any form of immunosuppressive therapy within 7 days before the first dose of study treatment.
• . Active autoimmune disease requiring systemic treatment within the past 2 years (e.g., use of disease-modifying drugs, corticosteroids, or immunosuppressive agents).