Table 4. Multivariate Cox proportional hazard regression model of breast cancer-specific survival (BCSS) and overall survival (OS) for the 1:1 matched surgery and non-surgery groups, stratified by the T stage, N stage, breast subtype and metastasis status.

Variablesb	Surgery vs. Non-surgerya
	BCSS		OS
	HR (95% CI)	P	HR (95% CI)	P
T stage
T1 + T2	0.492 (0.431–0.562)	<0.001	0.504 (0.443–0.572)	<0.001
T3 + T4	0.580 (0.521–0.646)	<0.001	0.594 (0.535–0.659)	<0.001
N stage
N0 + N1	0.528 (0.475–0.587)	<0.001	0.538 (0.486–0.596)	<0.001
N2 + N3	0.564 (0.493–0.646)	<0.001	0.585 (0.513–0.667)	<0.001
Breast subtype
HR+/HER2−	0.554 (0.489–0.628)	<0.001	0.573 (0.508–0.646)	<0.001
HR +/HER2+	0.462 (0.361–0.592)	<0.001	0.473 (0.372–0.601)	<0.001
HR −/HER2+	0.459 (0.346–0.609)	<0.001	0.490 (0.374–0.643)	<0.001
TNBC	0.536 (0.455–0.631)	<0.001	0.534 (0.455–0.627)	<0.001
Metastasis status
Bone-only metastasis	0.495 (0.423–0.580)	<0.001	0.501 (0.431–0.583)	<0.001
Visceral metastasis	0.562 (0.510–0.619)	<0.001	0.568 (0.517–0.625)	<0.001

Notes.

^aNon-surgery as a reference.

^bAdjusted by a multivariate Cox proportional model, including age, race, T stage, N stage, grade, molecular subtype, chemotherapy status, solitary bone or visceral metastasis where appropriate.