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

"1. Adelumab: 1200 mg on Day 1, every 3 weeks (q3w).~2. VEX Metronomic Chemotherapy:~ Vinorelbine: 20 mg orally, every other day, every 3 weeks (q3w). Cyclophosphamide: 50 mg orally, once daily, every 3 weeks (q3w). Capecitabine: 500 mg orally, three times daily, every 3 weeks (q3w).~3. Radiotherapy: The interval between radiotherapy and immunotherapy should be within 3 weeks, with no specific order required. Different radiotherapy techniques will be selected based on the size and location of the metastatic lesions:~Stereotactic Body Radiation Therapy (SBRT), Spatially Fractionated Radiation Therapy (SFRT), Low-dose Radiotherapy (LDRT)."

"1. Adelumab: 1200 mg on Day 1, every 3 weeks (q3w).~2. VEX Metronomic Chemotherapy:~ Vinorelbine: 20 mg orally, every other day, every 3 weeks (q3w). Cyclophosphamide: 50 mg orally, once daily, every 3 weeks (q3w). Capecitabine: 500 mg orally, three times daily, every 3 weeks (q3w).~3. Radiotherapy:~If there is intracranial disease progression but extracranial disease remains stable, the systemic treatment regimen of Adelumab + VEX metronomic chemotherapy will be continued, with the addition of intracranial radiotherapy.~If there is intracranial disease progression and extracranial disease progression, the systemic treatment regimen will be modified, with the addition of intracranial radiotherapy.~The radiotherapy positioning and techniques will be the same as those used in the experimental group."