Neratinib Combined With Fulvestrant and Eribulin in the Treatment ofHR+/HER2+ Advanced Breast Cancer

Inclusion Criteria: * Female patients aged ≥18 years and ≤75 years; * ECOG performance status of 0-2; * Histologically confirmed HR-positive/HER2-positive advanced breast cancer: * Definition of HER2 positivity: IHC 3+ or IHC 2+/ISH positive prior to T-DXd treatment; * Definition of HR positivity: ER or PR ≥1%; * Refractory to prior treatment containing T-DXd (definition of resistance: a. Definite disease progression per RECIST v1.1 criteria; b. Intolerance to T-DXd treatment); * Prior exposure to anthracyclines and taxanes (including use in the adjuvant/neoadjuvant setting); * Presence of at least one measurable lesion (per RECIST v1.1 criteria); * Estimated survival time ≥3 months; * Adequate function of major organs, meeting the following requirements (no blood transfusion, no use of leukocyte- or platelet-stimulating agents within 2 weeks prior to screening); * For premenopausal or non-surgically sterilized female patients: Agreement to abstain from sexual activity or use effective contraceptive methods during treatment and for at least 7 months after the last dose of study treatment; * Voluntary participation in the study, signing of the informed consent form, good compliance, and willingness to cooperate with follow-up. Exclusion Criteria: * Severe allergic reactions to neratinib, eribulin, fulvestrant, or any of their excipients; * Prior treatment with neratinib, other small-molecule anti-HER2 TKIs, or eribulin; * Patients with inflammatory breast cancer; * A histor…