Efficacy and Safety of Disitamab Vedotin Plus Pyrotinib or Naratinib in HER2-positive Breast Cancer Patients With Brain Metastasis

Treatment Plan After patient screening, patients will receive treatment with trastuzumab injection plus either pyrotinib maleate tablets or neratinib maleate tablets, with each cycle lasting 14 days until disease progression. Trastuzumab Injection: Intravenous infusion, initial loading dose of 2 mg/kg, administered via intravenous infusion over 30-90 minutes (usually recommended around 60 minutes), administered on day 1 of each cycle, with each cycle lasting 14 days. Pyrotinib Maleate Tablets: 400 mg, taken orally once daily, within 30 minutes after a meal, at the same time every day. Taken continuously, with each cycle lasting 14 days. If a patient misses a dose of pyrotinib, it should not be made up for, and the next dose should be taken as scheduled. Neratinib Maleate Tablets: 240 mg, taken orally once daily with a meal, at the same time every day. The neratinib tablet should be swallowed whole (it should not be chewed, crushed, or split before swallowing). Taken continuously, with each cycle lasting 14 days. If a patient misses a dose of neratinib, it should not be made up for, and the next dose should be taken as scheduled. Note: The choice between pyrotinib maleate tablets or neratinib maleate tablets for treatment should be based on the patient's previous treatment history as decided by the investigator. Treatment medication should be continued until disease progression or the occurrence of intolerable toxic reactions. Study Steps 1) Screening Period (Visit 1: -14 to -1 days, approximately 2 weeks): Subjects will sign an informed consent form during Visit 1 and undergo a series of examinations (see Table 1. Treatment Flowchart). Based on the examination results and inclusion/exclusion criteria, the investigator will determine if the subject meets the inclusion criteria and does not meet the exclusion criteria. 2) Treatment Period (Visit 2 to disease progression, 1 visit every 2 cycles): Subjects will receive treatment with trastuzumab injection plus pyrotinib maleate tablets plus capecitabine tablets on the experimental Day 0, with each cycle lasting 21 days, until disease progression. During this period, a series of examinations will be conducted every 2 cycles (see flowchart for visits 2 to N). The investigator will evaluate the effectiveness and safety of the treatment based on the subject's examination results. 3) Survival Follow-up Period (1 follow-up every 3 months after withdrawal from the study): After patients withdraw due to disease progression or other endpoint events, a telephone follow-up will be conducted every 3 months until the patient's death or loss to follow-up. Detailed records of disease progression, related treatments, and survival information should be documented.