Locoregional tumor burden and risk of mortality in metastatic breast cancer

The role of lymph node involvement and tumor size in metastatic disease including breast cancer is unclear. Here, nodal metastasis and T stage on the risk of mortality were investigated in de novo metastatic breast cancer population (35812 patients) in the Surveillance, Epidemiology, and End Results (SEER) Program database in the United States. We found an association between all-cause mortality and regional node involvement (adjusted hazard ratio [HR] = 1.45, 95% confidence interval [CI] 1.36–1.55, p < 0.0001) or T stage (HR = 1.20, 95% CI 1.14–1.25, p < 0.0001), independent of known clinicopathologic measurements. Number of positive nodes, and size and chest wall involvement of the breast tumors exhibited similar significance for breast cancer-specific mortality in the population (p < 0.0001 each), and all-cause mortality in hormone receptor (HR)-positive/HER2-negative (HR(+)/HER2(–)), HR(+)/HER2(+), HR(–)/HER2(+) and triple-negative metastatic breast cancer subtypes. Thus, nodal involvement and T stage are independent risk factors for mortality in the population of de novo metastatic breast cancer.