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.

Patients with advanced breast cancer who have already received and continue to use immunotherapy, or are planned to receive immunotherapy, and have been recommended for radiotherapy following evaluation by a multidisciplinary team (MDT) in the early stage and have completed radiotherapy, are registered and followed up in this study.