Table 2.

Univariate and multivariate analyses of overall survival (OS).

	overall survival (OS)
	Univariate				Multivariate
	P -value	HR	95% CI	95% CI	P -value	HR	95% CI	95% CI
Factor			Lower	Upper			Lower	Upper
Age at diagnosis (years)
<65	Reference				Reference
≥65	<0.001	2.051	1.593	2.642	<0.001	1.832	1.417	2.370
Marital status
Married	Reference				Reference
Unmarried and others	0.050	1.283	1.000	1.647	0.068	1.275	0.983	1.655
Race
White	Reference				–
Non-white	0.051	1.320	0.999	1.743
Sex
Female	Reference				Reference
Male	0.005	1.466	1.125	1.911	<0.001	1.867	1.417	2.459
Histology
SCC	Reference				Reference
Non-SCC	0.005	0.465	0.271	0.798	0.001	0.366	0.199	0.672
Differentiation
Well or fairly differentiated	Reference				–
Poorly or undifferentiated	0.819	0.966	0.717	1.301
Unknown	0.159	0.795	0.578	1.094
Tumor size (mm)
<41	Reference				–
≥41	0.135	1.260	0.931	1.707
Unknown	0.265	1.189	0.877	1.611
Clinical stage (AJCC 2002)
Stage I-II	Reference				–
Stage III	0.168	1.190	0.929	1.523
T stage
T1−2	Reference				–
T3−4	0.872	1.021	0.788	1.323
N stage
Negative	Reference				–
Positive	0.067	1.261	0.984	1.616
Surgery at the primary site
None	Reference				Reference
Yes	0.018	0.583	0.372	0.913	0.021	0.553	0.334	0.916
Regional lymphadenectomy
None/unknown	Reference				–
Yes	0.184	0.748	0.487	1.148
Radiotherapy
None/unknown	Reference				Reference
Yes	0.002	0.620	0.455	0.845	0.017	0.637	0.439	0.924
Chemotherapy
None/unknown	Reference				Reference
Yes	<0.001	0.473	0.362	0.618	<0.001	0.444	0.325	0.607

HR, hazard ratio; CI, confidence interval.