Table 3. Cox proportional hazards model for overall survival and CRC-specific survival of stage IV colorectal cancer patients.

Variables	Overall survival			CRC-specific survival
	HR	95 % CI	p value	HR	95 % CI	p value
Age	1.000 (referent)			1.000 (referent)
<70 years
≥70 years	1.15	1.083–1.226	<0.0001	1.130	1.058–1.206	0.0003
Gender	1.020	0.982–1.060	0.31	1.018	0.978–1.060	0.377
Ethnicity/race
White	1.000 (referent)			1.000 (referent)
Black	1.073	0.999–1.151	0.052	1.056	0.980–1.138	0.153
Hispanic	0.919	0.869–0.972	0.003	0.904	0.852–0.959	0.0008
Asian	0.966	0.908–1.030	0.28	0.934	0.875–0.998	0.0443
Native Americans	1.021	0.768–1.358	0.88	1.018	0.757–1.371	0.904
Histology
Adenocarcinoma	1.000 (referent)			1.000 (referent)
Mucinous	1.007	0.949–1.068	0.823	0.989	0.929–1.053	0.74
Others	1.070	0.834–1.373	0.60	0.977	0.743–1.285	0.87
Primary site
Proximal/transverse	1.000 (referent)			1.000 (referent)
Descending	0.777	0.706–0.855	<0.0001	0.801	0.725–0.885	<0.0001
Sigmoid	0.732	0.697–0.769	<0.0001	0.753	0.715–0.794	<0.0001
Rectosigmoid	0.715	0.668–0.765	<0.0001	0.726	0.676–0.780	<0.0001
Rectal	0.641	0.607–0.676	<0.0001	0.655	0.619–0.694	<0.0001
Time period
1996–1999	1.000 (referent)			1.000 (referent)
2000–2003	0.870	0.83–0.912	<0.0001	0.877	0.835–0.922	<0.0001
2004–2007	0.684	0.653–0.718	<0.0001	0.671	0.639–0.705	<0.0001
Tumor resection
No	1.000 (referent)			1.000 (referent)
Yes	0.417	0.398–0.436	<0.0001	0.429	0.409–0.450	<0.0001
Socioeconomic status
First quintile	1.000 (referent)			1.000 (referent)
Second quintile	0.948	0.885–1.015	0.127	0.975	0.906–1.049	0.490
Third quintile	0.904	0.844–0.968	0.037	0.947	0.881–1.0118	0.139
Fourth quintile	0.860	0.804–0.920	<0.0001	0.882	0.821–0.948	0.0007
Fifth quintile	0.823	0.769–0.882	<0.0001	0.871	0.810–0.937	0.0002