This study aims to explore the efficacy and safety of neratinib combined with fulvestrant and eribulin in the treatment of HR+/HER2+ advanced breast cancer after trastuzumab deruxtecan resistance. The treatment regimen of neratinib + fulvestrant + eribulin in this study is expected to provide a new and effective therapeutic strategy for patients with triple-positive breast cancer who develop resistance to trastuzumab deruxtecan, and offer novel therapeutic insights for advanced triple-positive breast cancer.