ERBB2 and breast cancer: Figure 1 indicated that BCLM patients (median OS, 31.4 months) had significantly poorer prognosis than non-BCLM patients (median OS, 50.0 months, P = 0.000) at first MBC diagnosis. The OS of BCLM patients stratified by breast cancer subtype was showed in Figure 2. BCLM patients with HR+/HER2− subtype had the longest survival (38.2 months) while triple-negative the shortest (18.0 months, P = 0.000). The median OS of BCLM patients with HR-/HER2+ (vs. HR+/HER2−, P = 0.282) and HR+/HER2+ (vs. HR+/HER2-, P = 0.518) subtypes were 29.0 and 31.9 months, respectively.