The aim of this trial is to explore the real-world patient-reported health-related quality of life (HRQOL), functioning, symptoms and symptom tolerability of sacituzumab govitecan or chemotherapy of the physician's choice for Chinese mTNBC patients. Evaluation of HRQOL and functioning using the EORTC QLQ-C30 and QLQ-BR45 questionnaires, including change from baseline and time to deterioration in each scale or item. Treatment-related symptoms and tolerability were assessed using the Patient-Reported Outcomes of the PRO-CTCAE and PGI-TT questionnaires.

Inclusion Criteria:

1. Patients aged over 18 years old.
2. Patients have been diagnosed with metastatic triple-negative breast cancer (mTNBC). ER, PgR, and HER2 status were determined locally by immunohistochemistry (IHC) of patients' primary or metastatic tumor sections. ER-negative and PgR-negative status was defined as≤1% staining in the nuclei by IHC. HER2-negative status was defined by IHC staining 0 to 1+ or fluorescence in situ hybridization ratio <2.0 if IHC 2+ or IHC not performed.
3. The metastatic disease was confirmed by clinical, imaging, histological, or cytological measures, including unresectable locally advanced breast cancer, de novo stage IV breast cancer, and recurrent metastatic breast cancer.
4. Patients who have received at least 1 prior regimen in the metastatic setting.
5. Plan to receive or has received sacituzumab govitecan monotherapy or chemotherapy of the physician's choice.
6. Available medical history.
7. All patients can provide an informed consent before enrolment and data collection.

Exclusion Criteria:

1. If participating in any controlled clinical trial, the subject cannot take part in this study.
2. HER2 overexpression or gene amplification, ie, immunohistochemistry (IHC) 3+ or fluorescence in situ hybridisation (FISH)+, where appropriate.
3. Pregnancy and lactation.
4. Severe hepatic impairment.

Patients have been diagnosed with metastatic triple-negative breast cancer (mTNBC). ER, PgR, and HER2 status were determined locally by immunohistochemistry (IHC) of patients' primary or metastatic tumor sections.