Table 2. Univariate and multivariate Cox proportional hazards analysis of overall survival for patients with primary OTSCC.

Variable	Univariate survival analysis				Multivariate survival analysis
	HR	95% CI	P value		HR	95% CI	P value
Smoking history (never, ever)	1.931	0.945–3.944	0.071		–	–	–
Pathologic stage (I–II, III–IV)	2.070	0.949–4.516	0.068		–	–	–
Pathologic T-stage (T1–T2, T3–T4)	2.756	1.436–5.287	0.002		2.795	1.353–5.755	0.005*
CA9 expression (low, high)	2.477	1.306–4.699	0.006		2.300	1.090–4.854	0.029*

HR >1, exposure factors can promote the occurrence of positive outcomes, which are risk factors; HR <1, exposure factor can prevent the occurrence of positive outcome and is a protective factor; *, P value <0.05. CI, confidence interval; HR, hazard ratio; OTSCC, oral tongue squamous cell carcinoma.