Table 2.

Multivariate analysis of overall survival.

	Model#1 (not including pack-years or p16 status; n=2688; 1611 deaths)		Model#2 (including p16 status and pack-years; n=1043; 556 deaths)		Model#3 (including interaction between p16 status and age; n=1043; 556 deaths)
	HR (95%CI)	p-value	HR (95%CI)	p-value	HR (95%CI)	p-value
Gender (male vs. female)	1.17(1.03–1.33)	0.02	1.10(0.88–1.37)	0.39	1.12(0.90–1.40)	0.30
Race (non-white vs. white)	1.18(1.05–1.33)	0.007	0.92(0.74–1.14)	0.44	0.92(0.74–1.14)	0.44
Zubrod performance status (1–2 vs. 0)	1.74(1.57–1.94)	<0.001	1.55(1.30–1.84)	<0.001	1.54(1.29–1.83)	<0.001
Primary site (non-OP vs. OP)	1.37(1.24–1.52)	<0.001	0.98(0.81–1.19)	0.83	0.99(0.82–1.90)	0.92
T stage (T4 vs. T1–3)	1.55(1.39–1.72)	<0.001	1.58(1.32–1.90)	<0.001	1.58(1.31–1.89)	<0.001
N stage (N2b-3 vs. N0–2a)	1.36(1.23–1.51)	<0.001	1.51(1.26–1.80)	<0.001	1.52(1.27–1.81)	<0.001
Smoking history (>10 vs. ≤ 10 pack-years)	-	-	1.83(1.46–2.30)	<0.001	1.81(1.44–2.28)	<0.001
p16 status (negative vs. positive)	-	-	2.21(1.79–2.72)	<0.001	-	-
p16 status (negative vs. positive) if age<70	-	-	-	-	2.34(1.88–2.91)	<0.001
p16 status (negative vs. positive) if age≥70	-	-	-	-	1.47(0.88–2.44)	0.14
Age (≥ 70 vs. <70)	1.53(1.34–1.76)	<0.001	1.46(1.14–1.88)	0.003	-	-
Age (≥ 70 vs. <70) if p16-positive	-	-	-	-	2.07(1.31–3.28)	0.002
Age (≥ 70 vs. <70) if p16-negative	-	-	-	-	1.30(0.97–1.75)	0.08
Interaction between p16 status and age	-	-	-	-	-	0.09

Cox models were stratified by trial (9003, 0129, 0522); CI, confidence interval; OP, oropharynx.