ERBB2 and breast carcinoma: It is also important not to make comparisons between different first line therapies, as taxane/pertuzumab/trastuzumab will have been reserved for the fitter patients with de novo HER2-positive breast cancer (or at least 12 months from completion of adjuvant chemotherapy/anti-HER2 therapy) and first line trastuzumab-emtansine for those relapsing within 6 months of adjuvant systemic therapy, representing very different populations of patients.