Table 2. Univariate and multivariate analysis of overall survival for the training cohort.

Characteristics	Univariate				Multivariate
	HR	95% CI	P value		HR	95% CI	P value
Year of diagnosis
2010–2014
2015–2019	1.490	0.735–3.024	0.269
Age at diagnosis, years
≤60
>60	1.483	0.774–2.843	0.235
Race
White
Asian	0.654	0.156–2.737	0.561
Black	1.042	0.405–2.682	0.931
Laterality
Left
Right	0.903	0.476–1.711	0.754
AJCC N stage
N1
N2+	2.441	1.286–4.631	0.006*		2.650	1.379–5.090	0.003*
ER
Negative
Positive	0.497	0.263–0.940	0.031*
PR
Negative
Positive	0.420	0.199–0.888	0.023*
HER–2
Negative
Positive	1.027	0.509–2.070	0.941
Tumor subtype
Luminal A
Luminal B	0.813	0.268–2.472	0.716
HER-2 positive	2.098	0.846–5.199	0.110
TNBC	1.911	0.898–4.066	0.093
Surgery
No
Yes	0.386	0.191–0.778	0.008*		0.359	0.177–0.725	0.004*
Radiotherapy
No/unknown
Yes	0.543	0.287–1.026	0.060*		0.416	0.217–0.799	0.008*
Chemotherapy
No/unknown
Yes	0.882	0.369–2.110	0.778

*, statistically significant. AJCC, American Joint Committee on Cancer; ER, estrogen receptor; PR, progesterone receptor; TNBC, triple-negative breast cancer.