ERBB2 and breast cancer: Although there are no randomized trials of ET versus not in the adjuvant setting for HER2+ early-stage breast cancer in the post-trastuzumab era, the observation that the specific type of ET in the Short-HER trial is significantly associated with long-term time-to-event clinical outcomes (i.e., DFS) strongly suggests that ET is impactful (compared to omission of anti-estrogen treatment) in patients with HER2+ early-stage disease in the adjuvant setting88.