Pyrotinib and Disitamab for Advanced HER2-positive Breast Cancer

Inclusion Criteria: 1. Aged ≥ 18 years old; 2. Histopathologically confirmed HER2-positive inoperable locally advanced or metastatic breast cancer; 3. Patients with first-line or second-line advanced disease: First-line advanced disease: no prior systemic therapy for locally advanced or metastatic disease. For patients who received neoadjuvant or adjuvant therapy, the disease-free interval (DFI) after the completion of the last chemotherapy or HER2-targeted therapy was more than 12 months; Second-line advanced disease: prior treatment with taxane combined with trastuzumab, with or without pertuzumab, in the advanced setting; or recurrence occurring during neoadjuvant/adjuvant therapy, or a disease-free interval (DFI) of ≤ 12 months after completion of the last neoadjuvant/adjuvant chemotherapy and HER2-targeted therapy; 4. Planned to receive pyrotinib-containing regimen, and judged by investigators based on clinical practice to have potential subsequent treatment with Ruikang trastuzumab after failure of pyrotinib-containing therapy; 5. Traceable medical records available throughout the treatment period. Exclusion Criteria: 1. Failure to sign the informed consent form; 2. Pregnant or lactating females; 3. Patients participating in any interventional clinical trial involving investigational drugs or marketed drugs at enrollment; 4. Other conditions deemed ineligible for enrollment by the investigator's judgment.