Table 2. Multivariate analysis using a Cox proportional hazards model in SCLC patients ≤ 80.

Variable	Multivariate analysis
	OS			CSS
	HR	95% CI	P	HR	95% CI	P
Race recode			<0.001			<0.001
White	Reference
Black	0.909	0.870 to 0.949	<0.001	0.896	0.856 to 0.938	<0.001
Other	0.909	0.849 to 0.974	0.007	0.884	0.822 to 0.951	0.001
Unknown	0.572	0.365 to 0.898	0.015	0.395	0.224 to 0.696	0.001
Sex			<0.001
Male	Reference
Female	0.885	0.863 to 0.908	<0.001	0.896	0.872 to 0.920	<0.001
Year of diagnosis			<0.001			<0.001
2012-2015	Reference
2008-2011	0.922	0.894 to 0.951	<0.001	0.924	0.894 to 0.955	<0.001
2004-2007	0.920	0.891 to 0.950	<0.001	0.933	0.903 to 0.965	<0.001
CHSDA Region			0.001			<0.001
NORTH	Reference
SOUTHWEST	0.946	0.902 to 0.992	0.023	0.946	0.900 to 0.993	<0.001
EAST	0.919	0.879 to 0.960	<0.001	0.907	0.866 to 0.949	<0.001
Primary Site			<0.001			<0.001
Main bronchus	Reference
Upper lobe	0.918	0.881 to 0.957	<0.001	0.913	0.874 to 0.953	<0.001
Middle lobe	0.899	0.834 to 0.969	0.005	0.880	0.814 to 0.952	0.001
Lower lobe	0.931	0.888 to 0.975	0.003	0.923	0.879 to 0.969	0.001
NOS	1.029	0.980 to 1.081	0.253	1.019	0.968 to 1.072	0.476
Overlapping lesion	1.011	0.913 to 1.120	0.836	0.996	0.896 to 1.108	0.941
Grade			<0.001			<0.001
Unknown	Reference
I	0.497	0.353 to 0.700	<0.001	0.491	0.341 to 0.708	<0.001
II	0.876	0.708 to 1.083	0.222	0.935	0.752 to 1.163	0.545
III	0.963	0.920 to 1.007	0.101	0.966	0.922 to 1.013	0.156
IV	0.982	0.950 to 1.014	0.265	0.986	0.953 to 1.020	0.43
Laterality			<0.001			<0.001
Bilateral, single primary	Reference
Right-origin of primary	1.092	0.985 to 1.211	0.096	1.058	0.952 to 1.175	0.297
Left-origin of primary	1.101	0.993 to 1.222	0.069	1.068	0.960 to 1.187	0.224
Paired sit	0.922	0.825 to 1.030	0.152	0.886	0.791 to 0.992	0.036
Only one side - side unspecified	0.827	0.691 to 0.991	0.04	0.779	0.645 to 0.941	0.010
Not a paired site	1.044	0.797 to 1.368	0.755	0.995	0.751 to 1.317	0.970
Stage Group			<0.001			<0.001
IV	Reference
III	0.653	0.633 to 0.673	<0.001	0.623	0.603 to 0.644	<0.001
II	0.521	0.465 to 0.583	<0.001	0.477	0.422 to 0.539	<0.001
I	0.307	0.283 to 0.333	<0.001	0.255	0.233 to 0.279	<0.001
Surgery			<0.001			<0.001
No	Reference
Yes	0.500	0.461 to 0.543	<0.001	0.495	0.453 to 0.540	<0.001
Radiation recode			<0.001			<0.001
No	Reference
Yes	0.685	0.664 to 0.706	<0.001	0.695	0.673 to 0.718	<0.001
Age at diagnosis	1.013	1.011 to 1.015	<0.001	1.012	1.010 to 1.013	<0.001
Marital status			<0.001			<0.001
Separated	Reference
Divorced	1.023	0.917 to 1.142	0.681	1.021	0.911 to 1.144	0.721
Single	1.011	0.906 to 1.128	0.839	0.997	0.890 to 1.117	0.956
Windowed	0.980	0.878 to 1.094	0.717	0.984	0.878 to 1.103	0.780
Unknown	0.912	0.807 to 1.030	0.137	0.918	0.808 to 1.041	0.182
Married	0.907	0.815 to 1.010	0.075	0.918	0.822 to 1.026	0.132
Unmarried or domestic partner	0.825	0.564 to 1.205	0.319	0.830	0.560 to 1.230	0.354
High school education			0.008			0.001
<7	Reference
7-12	1.001	0.943 to 1.062	0.975	1.007	0.947 to 1.071	0.833
13-20	1.001	0.939 to 1.067	0.967	1.015	0.950 to 1.085	0.659
>21	0.942	0.879 to 1.010	0.095	0.941	0.875 to 1.012	0.103
Median household income			<0.001			0.001
>63000	Reference
48000-62999	1.018	0.985 to 1.053	0.287	1.027	0.992 to 1.064	0.133
38000-47999	1.053	1.009 to 1.100	0.018	1.055	1.009 to 1.104	0.019
<38000	1.124	1.062 to 1.190	<0.001	1.131	1.066 to 1.200	<0.001
Chemotherapy recode			<0.001			<0.001
No	Reference
Yes	0.435	0.424 to 0.447	<0.001	0.436	0.424 to 0.448	<0.001

Abbreviations: SCLC: Small cell lung cancer; NOS: Not otherwise specified; HR: hazard ratio; CI: Confidence interval.