Distribution and Prognosis of Metastatic Disease in Newly Diagnosed Stage IV Breast Cancer

Background Thorough population-based estimates of the epidemiological features of metastatic disease in newly diagnosed stage IV breast cancer are lacking.

Methods Target patients were identified using the Surveillance, Epidemiology, and End Results (SEER) database. Logistic regression was used to estimate the odds ratios (ORs) for different metastasis patterns (bone, brain, liver and lung), stratified by sociodemographic and clinicopathological variables. Survival estimates were performed using the Kaplan-Meier method and the Cox regression.

Results A total of 356789 patients with breast cancer were included of which 18036 (5.06%) had stage IV disease. Bone metastasis had the highest composition ratio (42.6%). Patients with HR-/HER2+ subtype had the highest metastasis at diagnosis incidence proportions (1310/15062 [8.7%] of the entire cohort). Female breast cancer patients were more susceptible to bone metastasis, lung metastasis, and liver metastasis than male patients (all P<0.01). Hispanics were the most likely to have brain metastases (P<0.01). Compared with other subtypes, HR-/HER2- patients was the most likely to have lung metastases. Patients with bone metastasis displayed the longest median survival (27 months). Among patients with brain or liver metastases, Grade III patients had the worst prognosis (P<0.01). Among patients with lung metastasis, infiltrating duct mixed with other types of carcinoma (IDM) had a better prognosis than infiltrating duct carcinoma (IDC) (P<0.01). For liver metastases, TNM N0 stage patients had the highest risk of death, followed by N2 (P<0.01).

Conclusion We believe this is the most comprehensive analysis of the distribution and prognosis of metastatic disease in newly diagnosed stage IV breast cancer. It lends support to consideration of further studies evaluating the utility of modern screening strategies of the bone, brain, liver and lung among patient subsets at high risk for metastasis.