Eribulin Mesylate-based Therapy in Patients With Advanced HER2-negative Breast Cancer Previously Treated With ADC

Inclusion Criteria: 1. At least 18 years old; 2. Inoperable locally advanced or metastatic breast cancer; 3. Planning to use a single-agent or combination treatment regimen based on eribulin; 4. HER2 negative (IHC 0,+, or ++ but ISH negative); 5. Previously received ADC treatment at the local advanced or metastatic disease stage; 6. Previously received chemotherapy (including ADC) for local advanced or metastatic disease no more than 2 lines, where one treatment line is defined as completing at least one cycle of chemotherapy; 7. Eastern Cooperative Oncology Group (ECOG) performance status score (PS) 0-2; 8. The investigators have evaluated that the patient's organ and bone marrow functions are suitable for medication use and there are no relevant contraindications; 9. The subjects voluntarily join the study and sign the informed consent. Exclusion Criteria: 1. HER2-positive tumors 2. The hormone receptor status is unknown; 3. Patients who have received eribulin treatment before; 4. Those who have had other malignant tumors within the past 5 years (excluding the following situations: cured skin basal cell carcinoma, cervical carcinoma in situ, papillary thyroid carcinoma; second primary cancer that has been cured and has no recurrence within 5 years; subjects who have clearly identified the origin of the metastatic lesion as being from a certain primary tumor); 5. Mental illness or mental disorder, patients with poor compliance and inability to cooperate and describe treatment responses; 6. Pregnant or lactating women; 7. Other serious or uncontrollable diseases, or other conditions assessed by the researcher as not suitable for enrollment.