A Prospective, Multicenter, Observational Cohort Study Assessing the Efficacy and Safety of Radiotherapy-sensitized Immunotherapy in Advanced Breast Cancer

Inclusion Criteria: Subjects are eligible for inclusion in the study only if all the following criteria apply: 1. Men or women who are 18 years of age or older on the day of signing the informed consent; 2. Patients with advanced breast cancer that is inoperable or has metastasized, confirmed by histology or cytology; 3. Patients who, after MDT discussion at the metastatic breast cancer stage, are considered suitable for radiotherapy and have completed radiotherapy; 4. Patients who have previously received and continue to use immunotherapy, or are planned to receive immunotherapy, and are scheduled to receive a systemic treatment regimen including immunotherapy as chosen by the physician within 3 weeks after completing radiotherapy; 5. Patients with a traceable medical history during treatment; 6. Subjects who are able to sign an informed consent to participate in the study. Exclusion Criteria: 1. Subjects with brain metastases or leptomeningeal metastases; if there are any suspected symptoms or signs of CNS involvement, they should be excluded by a cranial MRI scan; 2. Have not signed the informed consent form; 3. Pregnant or lactating women; 4. Other conditions deemed unsuitable for inclusion in the study by the investigator.