Phase II Clinical Trial of PD-L1 in Combination With Vinorelbine + Cyclophosphamide + Capecitabine (VEX) Metronomic Chemotherapy With or Without Radiotherapy for Advanced Triple-negative Breast Cancer.

You may be eligible if

• Subjects are eligible to be included in the study only if all of the following criteria apply:
• 1. Male or female who is 18 years of age or older on the day of signing the informed consent form.
• 2. Subjects with metastatic triple-negative breast cancer, with clear clinical data records; specific reference to the "American Society of Clinical Oncology - College of American Pathologists (ASCO/CAP) guidelines."
• 3. Have received less than or equal to 1 line of chemotherapy for metastatic breast cancer;
• 4. Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 as assessed within 10 days before the start of study treatment;
• 5. Subjects must have at least one measurable lesion present; specific reference to the "Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST v1.1)" guidelines;
• 6. Subjects may have previously received treatment with anthracyclines (e.g., doxorubicin, epirubicin) and/or taxanes (e.g., paclitaxel, docetaxel) as follows: a) The subject has used anthracyclines and/or taxanes during adjuvant and/or neoadjuvant therapy before breast cancer recurrence. b) The subject has experienced treatment failure during or after chemotherapy based on anthracyclines and/or taxanes. c) According to the investigator's judgment, the Subject is not suitable for anthracyclines and/or taxanes-based chemotherapy as a first-line treatment option.
• 7. Female subjects are not pregnant, not lactating, and agree to use necessary contraceptive measures.
• 8. Subjects are able to sign an informed consent form to participate in the study.
• 9. Have appropriate organ function, as detailed in Table 1; all screening laboratory tests should be completed within 10 days before the start of study treatment.