HER2-Positive Breast Cancer is a type of breast cancer that tests positive for the human epidermal growth factor receptor 2 (HER2). Trastuzumab emtansine (T-DM1) is an antibody-drug comprising humanized monoclonal antibody trastuzumab linked to the cytotoxic agent DM1. T-DM1is can be effective in keeping cancer cells from growing, but its efficacy is treating women with HER2 positive breast cancer is not well studied. This study aims to examine the benefits of T-DM1in women with HER2 positive metastatic breast cancer.

This phase-3, open-label trial involved a total of 1,486 patients with HER2-positive early breast cancer with residual invasive disease. The patients were randomly assigned in a 1:1 ratio to receive adjuvant T-DM1 (n=743) or trastuzumab (n=743) for 14 cycles. The primary outcome of the study was invasive disease-free survival.

Invasive disease or death occurred in 91 patients in the T-DM1 group (12.2%) and 165 patients in the trastuzumab group (22.2%). Invasive disease-free survival at 3 years was 88.3% in the T-DM1 group and 77.0% in the trastuzumab group. Recurrence of disease occurred in 10.5% and 15.9% in the T-DM1 and trastuzumab, respectively.

The research concluded that in patients with HER2-positive early breast cancer, adjuvant T-DM1 lowered the risk of death or recurrence of invasive breast cancer by 50%, as compared with trastuzumab.

Ref: https://www.nejm.org/doi/full/10.1056/NEJMoa1814017