Journal of clinical oncology : official journal of the American Society of Clinical Oncology
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Targeted therapy with the humanized monoclonal antibody trastuzumab has become a mainstay for human epidermal growth factor receptor 2 (HER2) -positive breast cancer (BC). The mechanisms of action of trastuzumab have not been fully elucidated, and data available to date are reviewed here. The impact of the mechanisms of action on clinical benefit also is discussed. ⋯ Trastuzumab is the foundation of care for patients with HER2-positive BC. Emerging data from studies of other targeted agents may provide alternative treatment combinations to maximize the clinical benefit from trastuzumab and prevent or delay resistance. The continued development of trastuzumab highlights promising treatment approaches for the future.