Many regimens, including (1) a combination of single HER2-targeted agent with chemotherapy (C) (i.e., trastuzumab + chemotherapy (TC), pertuzumab + chemotherapy (PC), lapatinib + chemotherapy (LC)), (2) dual HER2-targeted agents with chemotherapy (i.e., pertuzumab + trastuzumab + chemotherapy (PTC), lapatinib + trastuzumab +chemotherapy(LTC)], or (3) dual HER2-targeted agents without chemotherapy (i.e., pertuzumab + trastuzumab (PT), trastuzumab emtansine + pertuzumab (T-DM1P)) have been used as neoadjuvant systemic therapies for early-stage or locally advanced breast cancers. The gene discussed is ERBB2; the disease is breast carcinoma.