TABLE 1.

Description of Study population and Hazards ratio from Cox univariate analysis for Overall Survival

	n (%)	HR	p-value
Center
1	264 (37)	1	ref
2	56 (8)	2.31 (1.27–4.20)	0.006
3	98 (14)	0.64 (0.25–1.66)	0.355
4	98 (14)	1.48 (0.73–3.02)	0.271
5	188 (27)	1.53 (0.86–2.70)	0.145
Age (years)
Mean (Standard Deviation)	57 (9.7)	1.05 (1.03–1.07)	<0.001
Sex
Male	589 (84)	1	ref
Female	115 (16)	1.67 (0.88–2.44)	0.142
Smoking*
Never	230 (45)	1	ref
Former	171 (34)	1.92 (1.08–3.41)	0.026
Current	107 (21)	2.49 (1.35–4.61)	0.004
Subsite
Tonsil	414 (59)	1	Ref
Base of tongue	276 (39)	1.15 (0.75–1.76)	0.528
Other§	14 (2)	1.75 (0.42–7.23)	0.440
Extranodal extension (pN> 0)
Negative	233 (35)	1	Ref
Positive	427 (65)	1.61 (0.98–2.63)	0.060
AJCC pathological stage
1	10 (1)	1	Ref
2	24 (3)	0.42 (0.03–6.64)	0.534
3	95 (14)	0.68 (0.08–5.44)	0.714
4	575 (82)	1.28 (0.18–9.22)	0.806
Pathological T-classification
1	279 (40)	1	Ref
2	290 (41)	1.77 (1.03–3.05)	0.039
3	92 (13)	2.67 (1.38–5.16)	0.004
4	43 (6)	5.69 (2.67–11.31)	<0.001
Pathological N-classification
0	44 (6)		Ref
1	91 (13)	0.89 (0.23–3.47)	0.870
2a	141 (20)	1.24 (0.35–4.40)	0.737
2b	337 (48)	1.89 (0.59–6.08)	0.285
2c	52 (7)	3.56 (1.01–12.62)	0.049
3	39 (6)	2.70 (0.64–11.31)	0.174
Positive Lymph nodes
≤4	589 (84)	1	Ref
≥5	115 (16)	2.93 (0.21–0.53)	<0.001
Margins*
Negative	543 (90)	1	Ref
Positive	61 (10)	1.55 (0.89–2.71)	0.123
Perineural Invasion*
Negative	367 (86)	1	Ref
Positive	60 (14)	3.33 (1.92–5.81)	<0.001
Lymphovascular Invasion*
Negative	307 (74)	1	Ref
Positive	109 (26)	1.92 (1.14–3.23)	0.014
Treatment#
Surgery only	147 (21)	1	Ref
Surgery + Radiation	322 (46)	0.54 (0.32–0.90)	0.019
Surgery + Chemoradiation	233 (33)	0.49 (0.27–0.87)	0.014

^*Variables with incompletely recorded data for study cohort.

^§Other subsites included soft palate in 10, the oropharynx subsite was unlisted in 4 patients.

^#Adjuvant therapy unknown for two patients, both did not have any recurrence and were alive at last follow-up.