ERBB2 and metastatic neoplasm: Observational studies between 2000 and 2015 in patients with HER2+ MBC showed that 12% in the US, 27–54% in Europe, and 27.1–49.2% of patients in China did not receive trastuzumab or any of the other HER2+ agents as first- and/or subsequent-line treatment for metastatic disease.