Incidence We identified 310789 patients with breast cancer diagnosed from 2010 to 2014. Stratified by molecular subtype, there were 61.7%,9.5%,4.1%,10.4%, 8.9% patients molecularly tested as HR+/HER2-, HR+/HER2+, HR-/HER2+, TNBC and unknown respectively. Among metastases to any site patients, there were 50%, 14%,7.6%,11% and 17.4% tested as HR+/HER2-, HR+/HER2+, HR-/HER2+, TNBC and unknown respectively. Within all included patients, 11300 had bone metastases which took up 3.6% of the entire cohort and 50 .5% of metastases patients. The highest incidence proportion was from the HR+/HER2+ (5.0%)and HR-/HER2+ (4.5%) cohort. (Shown in Table1). Based on our multivariable logistic regression analysis, HR+/HER2+ compared with HR+/HER2- (OR, 1. 19; 95% CI, 1. 06 -1. 35; P = 0. 003), N3 compared withN0 (OR, 2.76; 95% CI, 1.66-4.60; P < 0.01), metastases to brain compared with None (OR,4.03; 95% CI, 2. 67 -6. 09; p<0. 01), to lung compared with None (OR, 27.31 ; 95% CI, 20.06-37.17; p<0.01) and liver compared with None (OR, 10.45; 95% CI, 4.63-23.59; p<0. 01) were associated with higher possibility of developing bone metastases. Triple-Negative was associated with lower risk of bone metastases at diagnosis compared with HR+/HER2- (OR, 0. 72; 95% CI, 0. 64 -0. 82; P <0. 01). Other factors such as age, gender and marital status were not significantly related to developing bone metastases.(Shown in Table 2)
Survival According to eligible data, patients stratified by molecular subtype with follow-up during the study time were summarized in Table 1. As shown in Figure 1, among patients with bone metastases at diagnose, HR+/HER2+ experienced the longest survival time (41 months) and triple-negative patients had the shortest survival period (10 months). Figures comparing bone metastases (median survival 30 months) with lung (21 months), brain (11 months) and liver (19 months)was shown as Figure 2, Figure 3 and Figure 4. Comparing with other distal organ metastases, bone metastases had longer survival time. By performing Cox Regression Analysis, we identified age between 61 to 80 (vs. age 18-40; hazard ratio[HR],1. 79; 95% CI, 1. 68-1.91, p<0.01) and older than 80 (vs. age 18- 40; HR,5.32; 95% CI, 4.99-5.67, p<0.01), black race (vs. white; HR ,1. 35; 95% CI, 1. 30 -1. 39, p<0.01), molecular subtype as HR−/HER2+ (vs. HR+/HER2−; HR, 1. 55; 95% CI, 1. 48 -1. 63; p<0. 01) and Triple-negative (vs. HR+/HER2−;HR, 2. 60; 95% CI, 2. 52 -2. 68; p<0.01), lymph node statusN3(vs. N0; HR, 3. 21; 95% CI, 3. 09 -3. 35; p<0.01) , N2(vs. N0; HR, 2. 42; 95% CI, 2. 31 -2. 54; p<0.01) , N(vs. N0; HR, 1. 75; 95% CI, 1. 69 -1. 80; p<0.01), distal metastases to brain (vs. None; HR, 2. 22; 95% CI, 2. 07 -2. 40; p<0. 01), lung (vs. None; HR, 1. 97; 95% CI, 1. 88 -2. 07; p<0. 01) and liver (vs. None; HR, 2. 78; 95% CI, 264-2.92; p<0.01) as possible factors which were associated with greater all-cause mortality. Detailed data was shown in Table3. Briefly, increased mortality and poorer survival were associated with more extent distal metastases and specific molecular subtype. Moreover, we also identified married (vs. unmarried, HR, 0. 67; 95% CI, 0. 65 -0. 69, p<0. 01) and insured (vs. uninsured, HR, 0. 67; 95% CI, 0. 62 -0. 72, p<0. 01) status as protective factor of all-cause mortality.