Table 1. Clinicopathological characteristics, cause specific survival (CSS) and overall survival (OS) of SEER laryngeal cancer cases with pathological lymph node involvement.

Categorical variables	No. of patients	5-year CSS			5-year OS
	(n = 1963)	Rate (%)	Log-rank χ2	P value	Rate (%)	Log-rank χ2	P value
Race			3.965	0.138		5.289	0.071
White	1480 (75.4%)	43.7			33.9
Black	397 (20.2%)	38.8			29.7
Other	86 (4.4%)	48.1			40.9
Gender			2.795	0.095		1.545	0.214
Male	1526 (77.7%)	42.1			32.4
Female	437 (22.3%)	45.9			36.8
Year of diagnosis			0.390	0.823		0.228	0.892
1988–1994	429 (21.9%)	43.3			33.1
1995–2001	637 (32.5%)	42.4			34.0
2002–2008	897 (45.7%)	43.4			32.3
Primary site			15.271	0.009		15.803	0.007
Glottis	327 (16.7%)	40.9			32.5
Supraglottis	1285 (65.5%)	44.8			34.7
Subglottis	36 (1.8%)	0			32.1
Laryngeal cartilage	11 (0.6%)	32.7			24.2
Overlapping lesion	133 (6.8%)	41.0			29.6
Larynx, NOS	171 (8.7%)	36.0			28.7
Histological grade			17.037	0.002		21.628	<0.001
I	89 (4.5%)	44.4			34.3
II	937 (47.7%)	45.3			36.5
III	783 (39.9%)	42.2			31.6
IV	20 (1.0%)	46.1			20.0
Unknown	134 (6.8%)	27.9			22.3
Radiation sequence			33.328	<0.001		56.831	<0.001
No radiation	504 (25.7%)	35.4			23.7
Pre-operative	72 (3.7%)	38.3			28.9
Post-operative	1363 (69.4%)	45.9			37.2
Other	24 (1.2%)	38.3			27.3
Cancer directed surgery			26.251	<0.001		27.370	<0.001
Yes	1761 (89.7%)	44.5			34.8
Other	202 (10.3%)	26.1			18.6
T staging			59.303	<0.001		54.620	<0.001
T1	182 (9.3%)	57.7			46.2
T2	526 (26.8%)	48.5			36.1
T3	295 (15.0%)	42.1			34.7
T4a	809 (41.2%)	39.3			31.2
T4b	55 (2.8%)	29.6			20.3
Tx	96 (4.9%)	24.5			17.6
N staging			61.415	<0.001		47.574	<0.001
N1	546 (27.8%)	59.7			47.3
N2	1313 (66.9%)	37.1			28.8
N3	104 (5.3%)	31.9			20.6
M staging			55.169	<0.001		45.658	<0.001
M0	1845 (94.0%)	44.1			34.3
M1	89 (4.5%)	19.2			15.4
Mx	29 (1.5%)	40.8			29.4
Continuous variables	Median (range)
Age	60 years (17–91)
No. of LN examined	28(1–90)
No. of positive LNs	2(1–90)
Lymph node ratio	0.11(0.01–1.00)