Different Breast Cancer Subtypes Show Different Metastatic Patterns: A Study from A Large Public Database

BACKGROUND: Receptor status in breast cancer is known to be related to survival. However, the relationship between breast cancer subtype, preferential sites of metastasis, and overall survival is not clear. METHODS: A total of 414,528 patients from the National Cancer Database (2010-2013) were examined. All patients received surgery and systemic treatments. Breast cancer was subtyped based on hormonal receptor (HR) and HER2 status. RESULTS: HR-/HER2+ breast cancer patients had the highest overall rate of metastasis while HR+/HER2- had the lowest. HR+/HER2+ cancer had the most frequent metastasis to the bone, and HR-/HER2+ to brain, liver, lung and multiple sites. Generally, patients with brain or multiple metastasis had the worst overall survival (OS) across different subtypes. Patients with bone oligometastasis tend to have better OS than patients with metastasis to other site but significantly worse OS than patients without any metastasis. CONCLUSIONS: This large study exhibits how breast cancer subtype plays a role in the rate and site of metastasis as well as in overall survival. Surveillance and treatment strategies should be tailored on the risk and potential site of metastases based upon receptor subtype.