ERBB2 and metastatic neoplasm: The patterns of frontline treatment for metastatic disease were similar between the groups, with 1812 patients (44.4%) in the ERBB2-low group and 3859 patients (47.1%) in the ERBB2-zero group receiving endocrine-based therapy, and 2271 patients (55.6%) in the ERBB2-low group and 4329 patients (52.9%) in the ERBB2-zero group receiving chemotherapy.