ERBB2 and breast cancer: As an adjuvant treatment for early stage HER2+ breast cancer patients with node-positive disease or a tumour ≥ 1 cm, a 12-mo regimen of trastuzumab therapy compared with chemotherapy alone reduces the risk of death by a third (hazard ratio [HR] for overall survival [OS] = 0.66; 95% CI 0.57–0.77), although (usually reversible) cardiac dysfunction may occur [5].