Real-world Study of Sacituzumab Govitecan Monotherapy or Combination Therapy in Recurrent or Metastatic HER2-negative Breast Cancer

Inclusion Criteria: 1. Age and Gender Male or female aged 18 years or older. 2. Pathological Diagnosis and Classification Criteria (Must Meet Either Cohort Condition) 2.1 Triple-Negative Breast Cancer (TNBC) Cohort Histologically/cytologically confirmed triple-negative breast cancer (TNBC) by pre-SG biopsy/pathology report, with the following criteria: HER2-negative: Immunohistochemistry (IHC) score of 0 or 1+; if IHC score is 2+, HER2 negativity must be confirmed by fluorescence in situ hybridization (FISH). Estrogen and progesterone receptor-negative: \<1% of cells express hormone receptors as determined by IHC. Presence of locally advanced, recurrent, or metastatic disease (locally advanced disease must be confirmed by investigators as ineligible for curative resection). 2.2 Hormone Receptor-Positive/HER2-Negative Breast Cancer (HR+/HER2- BC) Cohort Histologically/cytologically confirmed HR+/HER2- breast cancer by pre-SG biopsy/pathology report, with the following criteria: HER2-negative: Immunohistochemistry (IHC) score of 0 or 1+; if IHC score is 2+, HER2 negativity must be confirmed by fluorescence in situ hybridization (FISH). HR-positive: Hormone receptor positivity (HR, including ER or PR status) is defined as ≥1% cell expression by IHC. Presence of locally advanced, recurrent, or metastatic disease (locally advanced disease must be confirmed by investigators as ineligible for curative resection). 3. Treatment Protocol Requirements Planned to receive SG monotherapy or combination therapy. 4. Other Enrollment Criteria Willing to participate in the study, sign the informed consent form, and demonstrate good compliance. Exclusion Criteria: 1. Pregnant or lactating women. 2. Known allergy to sacituzumab govitecan (SG) or any of its components. 3. History of other malignancies, except the following: Cured basal cell carcinoma, squamous cell skin carcinoma, cervical in situ carcinoma, or papillary thyroid carcinoma. A second primary cancer that has been completely cured with a tumor-free interval of ≥5 years. Other malignancies where the primary tumor source of metastatic foci has been clearly identified by investigators. 4. Diagnosis of other malignancies within the past 5 years 5. Current participation in other interventional clinical studies. 6. Presence of acute or chronic infections, or coexisting serious diseases (such as decompensated heart, lung, liver, or renal failure), assessed by investigators as incompatible with tolerating the study treatment. 7. Mental illness or psychiatric disorders leading to poor compliance, inability to cooperate with the study, or inability to describe treatment responses. 8. Modification of the treatment regimen after SG administration for reasons other than disease progression. 9. Any other circumstances deemed by investigators as likely to interfere with study evaluation, affect subject safety, or render the patient unsuitable for enrollment.