Table 2. Univariate and multivariate associations between patient characteristics and survival.

Characteristic	Hazard ratio (95% CI)	P value
Univariate associations
Age: ≥65 vs. <65	2.1 (1.2-3.9)	0.014*
Age: continuous	1.0 (1.0-1.1)	0.009*
Gender: female vs. male	0.9 (0.5-1.6)	0.771
ECOG: ≥1 vs. 0	1.2 (0.6-2.4)	0.565
Histologic grade: poorly differentiated vs. other	1.2 (0.6-2.5)	0.61
Tumor diameter: maximum cm (continuous)	1.1 (1.0-1.2)	0.202
Tumor diameter: >3 vs. ≤3 cm	1.2 (0.6-2.2)	0.636
Adjuvant therapy received: no vs. yes	2.1 (1.2-3.8)	0.013*
Lymph node involvement at resection: yes vs. no	2.3 (1.0-4.9)	0.038*
T stage: T2 vs. ≥T3	0.9 (0.4-1.9)	0.8
Positive margin at resection: yes vs. no	2.1 (1.1-3.9)	0.016*
Lymphovascular invasion: yes vs. no	2.2 (1.1-4.5)	0.027*
Perineural invasion: yes vs. no	3.2 (1.3-8.3)	0.013*
Multivariate associations
Adjuvant therapy received: no vs. yes	3.6 (1.8-7.0)	<0.001*
Positive margin at resection: yes vs. no	3.5 (1.8-6.8)	<0.001*
Lymph node involvement at resection: yes vs. no	3.5 (1.5-8.2)	0.004*
Age: continuous	1.0 (1.0-1.1)	0.035*

*, P<0.05. For categorical variables, the second group is the reference group for the Cox proportional hazard analysis. CI, confidence interval; ECOG, Eastern Cooperative Oncology Group.