Abstract
In February 2013, ado-trastuzumab emtansine (T-DM1, Kadcyla®) received regulatory approval in the United States for treatment-refractory human epidermal growth factor receptor 2 (HER2) positive metastatic or locally advanced breast cancer based on results from EMILIA, a large phase III trial that compared standard of care lapatinib plus capecitabine to T-DM1. Several other studies have been reported in the metastatic setting and multiple trials are ongoing or planned in the neoadjuvant, adjuvant and advanced disease settings. Here we provide an updated and comprehensive review of clinical trials evaluating T-DM1, discuss management of toxicity associated with this drug, propose potential mechanisms of resistance and offer practical considerations for the treating oncologist.