Long-term efficacy of adjuvant trastuzumab emtansine for stage I HER2-positive breast cancer: 5-year results from ATEMPT

Long-term outcomes of patients with stage I HER2-positive breast cancer receiving adjuvant trastuzumab emtansine (T-DM1) are undefined and predictive biomarkers represent an unmet need. The multicenter phase 2 ATEMPT trial randomized stage 1 HER2-positive breast cancer to one year of T-DM1 or paclitaxel plus trastuzumab. Five-year outcomes of the T-DM1 arm have now been published. T-DM1 resulted in outstanding invasive disease-free survival, recurrence-free interval, overall survival, and breast cancer-specific survival. Among patients with sufficient tissue for HER2DX testing, HER2DX risk score was significantly associated with 5-year recurrence risk. The authors conclude that adjuvant T-DM1 for one year leads to excellent long-term outcomes among patients with stage I HER2-positive breast cancer. A high HER2DX risk score predicted higher risk of recurrence.