Table 4.

Cox proportional hazard regression model of BCSS and OS comparing two studied groups, stratified by clinical variables after PSM.

Variables	Without adjuvant chemotherapy vs. adjuvant chemotherapya
	BCSS		OS
	HRb (95% CIc)	Cox p	HR (95% CI)	Cox p
Age (years old)
<50	1.819 (0.164–20.129)	0.626	1.819 (0.164–20.129)	0.626
≥50	0.579 (0.052–6.382)	0.655	0.522 (0.161–1.695)	0.279
Race
White	0.371 (0.039–3.568)	0.391	0.367 (0.099–1.355)	0.132
Black	63.819 (0.000–6.149E8)	0.612	1.195 (0.074–19.377)	0.900
Others	70.475 (0.000–6.90E8)	0.604	69.848 (0.001–6.114E6)	0.465
Marital status
Married	1.097 (0.069–17.565)	0.948	0.360 (0.073–1.786)	0.211
Not married	1.092 (0.153–7.766)	0.930	1.124 (0.281–4.500)	0.869
Grade
I + II	1.102 (0.069–17.625)	0.945	1.122 (0.226–5.559)	0.888
III + IV	1.086 (0.153–7.714)	0.934	0.477 (0.123–1.848)	0.284
Surgery type
BCSd	0.017 (0.000–1.742E5)	0.622	0.421 (0.082–2.169)	0.301
Mastectomy	1.832 (0.305–10.990)	0.508	0.980 (0.263–3.653)	0.976
Radiotherapy
No	3.583 (0.372–34.481)	0.269	0.671 (0.196–2.294)	0.525
Yes	0.016 (0.000–1,437.674)	0.479	0.676 (0.113–4.050)	0.668

^aGroup without adjuvant chemotherapy is reference.

^bHazard ratio.

^cConfidence interval.

^dBreast-conserving surgery.