Table 2.

The results of univariate and multivariate Cox regression analyses on variables

Variables	Univariate analysis		Multivariate analysis
	Hazard ratio (95% CI)	P value	Hazard ratio (95% CI)	P value
Age	1.030 (1.024–1.035)	< 0.001	1.021 (1.015–1.028)	< 0.001
Race
White	Reference		Reference
Black	1.416 (1.153–1.739)	< 0.001	1.476 (1.191–1.828)	< 0.001
Others	1.002 (0.760–1.320)	0.989	1.190 (0.900–1.574)	0.222
Marital status
Married	Reference		Reference
Unmarried	1.512 (1.301–1.757)	< 0.001	1.267 (1.084–1.479)	0.003
Grades
I	Reference
II	0.782 (0.526–1.163)	0.225
III	0.873 (0.588–1.294)	0.498
Unknown	1.124 (0.738–1.711)	0.586
Tumor size	0.9991 (0.9932–1.005)	0.778
T Stage
T1	Reference
T2	1.072 (0.910–1.264)	0.403
N stage
N0	Reference		Reference
N1	0.756 (0.649–0.881)	< 0.001	0.921 (0.787–1.079)	0.309
Laterality
Left	Reference
Right	1.021 (0.879–1.186)	0.785
ER
Negative	Reference		Reference
Positive	0.650 (0.554–0.762)	< 0.001	0.595 (0.480–0.739)	< 0.001
PR
Negative	Reference		Reference
Positive	0.683 (0.588–0.793)	< 0.001	0.725 (0.593–0.888)	0.002
HER2
Negative	Reference		Reference
Positive	0.531 (0.453–0.623)	< 0.001	0.534 (0.448–0.636)	< 0.001
Surgery
No	Reference		Reference
Yes	0.627 (0.517–0.759)	< 0.001	0.740 (0.608–0.900)	0.003
Chemotherapy
No	Reference		Reference
Yes	0.489 (0.417–0.574)	< 0.001	0.628 (0.522–0.755)	< 0.001
Radiotherapy
No	Reference
Yes	1.174 (0.988–1.396)	0.068
Brain metastatic
No	Reference		Reference
Yes	2.298 (1.810–2.917)	< 0.001	2.061 (1.603–2.650)	< 0.001
Lung metastatic
No	Reference		Reference
Yes	1.560 (1.324–1.838)	< 0.001	1.158 (0.972–1.378)	0.100
Bone metastatic
No	Reference		Reference
Yes	1.350 (1.161–1.570)	< 0.001	1.235 (1.054–1.447)	0.009
ICD-O-3
8500	Reference
Others	1.134 (0.942–1.365)	0.183