Table 2. Univariate Cox proportional hazards analysis of potential factors affecting survival.

Variable	Wald	HR (95% CI)	p a	Details	Median		1-, 3-, 5-year survival rate	Overall comparison
					Estimate	95%CI		Chi-Square	df	p b for log-rank
Total					48.00	29.26-66.74	0.929, 0.788, 0.671
Age	0.55	1.16 (0.78-1.72)	0.460	<60	59.00	30.05-87.95	0.85, 0.584, 0.414
				≥60	48.00	29.86-66.14	0.867, 0.633, 0.507	0.556	1	0.456
Laryngectomy	17.64	2.35 (1.58-3.49)	<0.001*	PL	73.00	50.84-95.16	0.885, 0.73, 0.632
				TL	30.00	21.32-38.68	0.818, 0.468, 0.27	18.96	1	<0.001*
Neck dissection	1.69	0.71 (0.43-1.19)	0.194	ND	36.00	-	0.676, -, -
				NND	56.00	36.32-75.69	0.91, 0.752, 0.583	1.73	1	0.188
Differentiation	8.99		0.011*	HD	71.00	15.55-126.45	0.676, -, -
	0.07	0.93 (0.57-1.57)	0.794	MD	59.00	39.14-78.86	0.912, 0.712, 0.602
	5.44	2.39 (1.15-4.99)	0.02*	LD	15.00	0.00-33.33	0.214, -, -	9.78	2	0.008*
T	14.07	2.17 (1.45-3.25)	<0.001*	T1-T2	77.00	56.18-97.82	0.882, 0.695, 0.616
				T3-T4	32.00	22.25-41.75	0.824, 0.483, 0.243	14.96	1	<0.001*
N	17.04	2.39 (1.58-3.62)	<0.001*	N0	71.00	48.28-93.73	0.897, 0.706, 0.6
				N1-N2	26.00	14.08-37.92	0.796, 0.403, -	18.33	1	<0.001*
Clinical stage	26.86	3.29 (2.10-5.18)	<0.001*	I-II	98.00	67.49-128.51	0.849, 0.732, 0.527
				III, IV	32.00	24.2-39.8	0.897, 0.649, 0.418	30.15	1	<0.001*

a. p for Wald test < 0.05 indicates statistical significance for individual coefficients

b. p for Log-rank Test < 0.05 indicates statistical significance for grouping variables

Abbreviations: PL: Partial laryngectomy; TL: Total laryngectomy; ND: Neck dissection; NND: Non-neck dissection; HD: High differentiation; MD: Moderate differentiation; LD: Low differentiation; df: degrees of freedom. *: indicates statistical significance