Table 2.

Univariate and multivariate Cox regression analysis using the LND as a categorical variable

Variable	Univariate analysis			Multivariate analysis
	HR	95% CI	P-value	HR	95% CI	P-value
Age	1.045	1.03–1.06	<0.001	1.049	1.032–1.065	<0.001
Sex
Male	Reference
Female	0.961	0.702–1.317	0.806
Race
White	Reference			Reference
Black	1.22	0.811–1.836	0.34	1.268	0.842–1.91	0.256
Other	1.802	1.015–3.202	0.044	1.992	1.103–3.595	0.022
LNs examined	0.984	0.954–1.015	0.303
SEER stage
Localized	Reference			Reference
Regional	1.701	1.115–2.593	0.014	1.467	0.939–2.29	0.092
Distant	3.839	2.578–5.717	<0.001	2.893	1.85–4.514	<0.001
Tumor laterality
Unilateral	Reference			Reference
Bilateral	1.988	1.127–3.51	0.018	2.014	1.111–3.653	0.021
Year of diagnosis
1988	Reference
1989–1997	2.836	0.387–20.778	0.305
1998–2000	3.798	0.503–28.656	0.196
2000–2014	3.156	0.434–22.957	0.256
LND stratification
Low LND	Reference			Reference
High LND	2.804	1.998–3.934	<0.001	2.102	1.44–3.07	<0.001

Abbreviations: HR, hazard ratio; LNs, lymph nodes; LND, lymph node density; SEER, Surveillance, Epidemiology, and End Result.