Primary Prevention of Thrombocytopenia Associated With T-DM1 Therapy in HER2 Positive Breast Cancer With Herombopag

Inclusion Criteria: 1. Female, age ≥18 years; 2. Histopathologically or cytologically confirmed diagnosis of breast cancer; 3. Tumor tissue confirmed as HER2-positive, defined as immunohistochemistry (IHC) showing +++, or IHC++ with fluorescence in situ hybridization (FISH) demonstrating HER2-positive status; 4. Planned to receive T-DM1 regimen based on clinical judgment; 5. ECOG PS score: 0-2; 6. Expected survival greater than 12 weeks; 7. Adequate organ and bone marrow function. Exclusion Criteria: 1. A confirmed history of severe allergic reactions to the active ingredients or excipients of the therapeutic drug; 2. Presence of other underlying diseases or comorbidities causing thrombocytopenia, such as aplastic anemia, immune thrombocytopenia, myelodysplastic syndrome, etc.; 3. Individuals with hereditary bleeding disorders, coagulation dysfunction, high bleeding risk, or a history of thrombotic events (e.g., transient ischemic attack, cerebral hemorrhage, cerebral infarction, pulmonary embolism) within 6 months prior to initial medication use; 4. Individuals with uncontrolled hypertension and a history of hypertensive crisis or hypertensive encephalopathy; 5. Pregnant or lactating women; 6. Presence of multiple factors affecting oral drug absorption, such as dysphagia, nausea/vomiting, chronic diarrhea, or intestinal obstruction; 7. History of severe psychiatric disorders, substance abuse, alcoholism, or drug addiction; 8. Currently participating in interventional clinical research treatment, or having received other investigational drugs or devices within 4 weeks prior to first dosing (individuals who failed screening for other clinical trials may be included in this study); 9. Any other factors deemed by the investigator to increase study risk, affect patient compliance with the protocol, or impact the patient's ability to complete the trial, such as physiological or psychological conditions that make participation in this study inappropriate;