Comparison of patterns and prognosis among distant metastatic breast cancer patients by age groups: a SEER population-based analysis

Abstract

To investigate the effects of age at diagnosis on metastatic breast cancer and patients' prognosis, we collected patient data from the Surveillance, Epidemiology, and End Results (SEER) database. We finally identified 4932 eligible metastatic breast cancer patients diagnosed between 2010-2013, including 850 younger patients (<50 years), 2,540 middle-aged patients (50-69 years) and 1,542 elder patients (>69 years). The results revealed that in stage IV patients, elder patients were more likely to have lung metastasis (P < 0.001) and less likely to have only distant lymphatic spread (P = 0.004). Higher proportion of younger (34.9%) and middle-aged (36.2%) patients had multiple metastatic sites than elder patients (28.3%) (P < 0.001). In survival analysis, younger patients presented the best prognosis, while elder patients had the worst both in overall survival (χ² = 121.9, P < 0.001) and breast cancer-specific survival (χ² = 69.8, P < 0.001). Age at diagnosis was an independent prognostic factor for metastatic breast cancer patients. Moreover, patients with bone metastasis only had superior survival compared to other metastatic patients (P < 0.001). Brain metastasis only group and multiple sites metastasis group had the poorest prognosis (P < 0.05). We hope the results will provide insights into a better understanding of distant metastatic breast cancer.

Figure 1

Comparison of survival in younger, middle-aged and elder metastatic breast cancer patients. Kaplan Meier analysis for overall survival (OS, χ² = 121.9, P < 0.001, Fig. 1A) and breast cancer-specific survival (BCSS, χ² = 69.8, P < 0.001, Fig. 1B) were shown in the graph. The prognosis became worse with the increase of age. The 1-year, 2-year survival rate and median survival time (MST) were listed respectively in the table below the graph.

Figure 2

Comparison of survival in breast cancer patients with different hormone receptor status. Kaplan Meier analysis for OS and BCSS in different subgroups were shown in the graph. In hormone receptor positive (A,B) patients, the prognosis became worse with the increase of age (P < 0.001). In hormone receptor negative patients (C,D), middle-aged patients had similar survival to younger patients (P > 0.05), though older patients still had the worst prognosis. HoR+: hormone receptor positive; HoR-: hormone receptor negative.

Figure 3

Comparison of survival in breast cancer patients with single or multiple metastatic sites. Kaplan Meier analysis for OS (χ² = 147.7, P < 0.001, Fig. 2A) and BCSS (χ² = 145.7, P < 0.001, Fig. 2B) were shown. The 1-year, 2-year survival rate and median survival time (MST) were listed respectively in the table below the graph. MST: median survival time.