SC trastuzumab for human epidermal growth factor receptor 2 (HER2)-positive breast cancer had non-inferior PK (meeting the prespecified margin for the difference between groups in Ctrough of 0.8) and efficacy (meeting the prespecified margin for the difference between groups in pathological complete remission of − 12.5%), compared with IV administration, in a phase III, randomised, open-label trial in patients with early HER2-positive breast cancer [19]. Here, ERBB2 is linked to breast cancer.