Table 4. Multivariate analysis of the prognostic factors for disease-free survival.

	Multivariate analysis
	HR	95% CI	P value
Disease-free survival
7th AJCC edition			<0.001
IA	Ref
IB	0.999	0.728–1.372
IIA	1.444	1.082–1.926
IIB	1.862	1.383–2.508
IIIA	2.735	2.030–3.685
IIIB	4.575	3.470–6.034
IIIC	6.706	4.981–9.028
Age	1.677	1.429–1.967	<0.001
Gender	1.235	1.046–1.458	0.013
Tumor size	1.135	0.965–1.334	0.126
Lymphovascular invasion	1.454	1.205–1.755	<0.001
Disease-free survival
8th AJCC edition			<0.001
IA	Ref
IB	1.015	0.739–1.393
IIA	1.481	1.109–1.977
IIB	1.888	1.397–2.550
IIIA	2.886	2.177–3.827
IIIB	5.014	3.752–6.699
IIIC	7.825	5.794–10.567
Age	1.018	1.010–1.025	<0.001
Gender	0.883	0.720–1.084	0.235
Tumor size	1.124	0.955–1.321	0.159
Lymphovascular invasion	1.404	1.161–13698	<0.001

AJCC: American Joint Committee on Cancer; C-index: Harrell concordance index