Prognostic significance of molecular subtype, metastatic site and primary tumor surgery for survival in primary metastatic breast cancer: A SEER-based study

The incidence of primary metastatic breast cancer (PMBC) has not decreased despite the increasing popularity of mammography screening and data on the survival among these patients are limited. Therefore, we conducted an extensive population-based study to investigate the factors influencing the survival of patients with PMBC. We identified 14,306 patients with de novo stage-IV breast cancer using the Surveillance, Epidemiology, and End Results data from 2010 to 2015. The overall survival (OS) time and breast cancer-specific survival (BCSS) time were compared by the Kaplan-Meier method. Univariate and multivariate analyses were performed to determine the effect of different prognostic factors. Patients with hormone receptor positive/human epidermal growth factor receptor 2 positive showed the longest median survival time in OS (39 months) and BCSS (43 months), and those with triple negative exhibited the shortest in OS (11 months) and BCSS (12 months). We concluded that patients who had undergone primary tumor surgery had better survival than those who did not. The incidence of distant visceral metastasis in the whole cohort was as follows: bone, lung, liver, and brain. This study also substantiated that patients with only brain metastasis had poorer survival than patients with metastasis at multiple sites metastasis, not including brain metastasis (P < .0001). This study confirmed that molecular subtypes, metastatic site and primary tumor surgery were associated with the survival of PMBC patients.