The Early Breast Cancer Trialists’ Collaborative Group (EBCTCG)'s ongoing extensive searches of bibliographic databases, including MEDLINE, Embase, the Cochrane Library, and meeting abstracts, up to March 31, 2020, identified seven trials comparing chemotherapy plus trastuzumab, a humanised IgG1 monoclonal antibody that targets the extracellular domain of the HER2 protein, with the same chemotherapy alone for early-stage, HER2-positive breast cancer. Here, ERBB2 is linked to breast carcinoma.