ERBB2 and breast cancer: Stage IV HR−/HER2- breast cancer patients with bone metastases experienced the shortest survival (median OS: 11 months; 95% CI: 9.9–12.1 months), whereas stage IV HR+/HER2+ breast cancer patients with bone metastases experienced the longest survival, with a median OS of 52 months (95% CI was not estimable; P < 0.001).