Table 3. Multivariable proportional hazard model without propensity score adjustment (N = 7,288).

Covariate	Level	HR	95 % CI Low	95 % CI High	HR p value
Age at diagnosis	≤50 y	0.689	0.632	0.751	<0.001
	50–65 y	0.791	0.731	0.857	<0.001
	65–75 y	0.886	0.821	0.955	0.002
	>75 y	–	–	–	–
Median income, 2000	<$30,000	1.170	1.077	1.272	<0.001
	$30,000-$34,999	1.089	1.010	1.174	0.027
	$35,000-$45,999	1.025	0.963	1.092	0.441
	>$46,000	–	–	–	–
Year of diagnosis	1998	1.078	0.993	1.171	0.073
	1999	1.026	0.947	1.112	0.524
	2000	1.020	0.942	1.104	0.628
	2001	0.935	0.867	1.009	0.085
	2002	–	–	–	–
Facility volume (unit = 50)		0.962	0.941	0.983	<0.001
Facility typea	CCP	1.104	1.002	1.217	0.047
	CCCP	1.064	1.002	1.131	0.044
	ARCP	–	–	–	–
Primary site	Head	1.160	0.958	1.405	0.128
	Body	1.172	0.938	1.465	0.162
	Tail	0.930	0.751	1.151	0.505
	Body/tail	–	–	–	–
Tumor size	≤25 mm	0.733	0.677	0.794	<0.001
	25–35 mm	0.884	0.815	0.959	0.003
	35–45 mm	0.942	0.863	1.029	0.187
	>45 mm	–	–	–	–
Stage	I	0.592	0.520	0.674	<0.001
	II	0.809	0.715	0.916	<0.001
	III	0.806	0.732	0.886	<0.001
	IV	–	–	–	–
Grade	Unspecified	0.441	0.395	0.492	<0.001
	I	0.455	0.413	0.501	<0.001
	II	0.768	0.725	0.813	<0.001
	III/IV	–	–	–	–
Surgical margin positive	No	0.709	0.668	0.753	<0.001
	Yes	–	–	–	–
LN positive	No	0.724	0.641	0.818	<0.001
	Yes	–	–	–	–
No. of examined LNs > 12	No	1.109	1.046	1.175	<0.001
	Yes	–	–	–	–
Adjuvant therapy	ChemoRad	0.784	0.739	0.831	<0.001
	ChemoOnly	1.076	0.977	1.186	0.139
	No adjuvant therapy	–	–	–	–

The model was built by backward elimination with a staying p value of <0.05. The starting list contains all variables that demonstrated significance at the 0.05 level in <T2>Table 2

HR hazard ratio, CI confidence interval, LN lymph node, ChemoOnly chemotherapy only, ChemoRad adjuvant chemoradiotherapy

^aCCP Community Cancer Program, CCCP Comprehensive Community Cancer Programs, ARCP Academic/Research Cancer Program, all as defined by the Commission on Cancer