Table 5.

Cox Proportional Hazards Model of Breast Cancer‐Specific Death in Patients With Stage IV Breast Cancer From the Surveillance, Epidemiology, and End Results 9 Registries, 1990 to 2011

Variable	HzR	95% CI	P
SEER 9 registries, n = 14,052
Surgery
No		Reference
Yes	0.58	0.55, 0.61	<.001
Diagnosis year
1990‐1998		Reference
1999‐2004	0.83	0.78, 0.89	<.001
2005‐2011	0.69	0.65, 0.73	<.001
Age, y
≥70		Reference
<70	0.76	0.72, 0.81	<.001
Chemotherapy
No		Reference
Yes	0.92	0.87, 0.96	.001
Radiation therapy
No		Reference
Yes	1.02	0.97, 1.07	.479
Hormone receptor status
Negative		Reference
Positive	0.47	0.44, 0.49	<.001
Race
Nonwhite		Reference
White	0.83	0.79, 0.88	<.001
SEER 9 without the S‐PS region
S‐PS region	0.87	0.84, 0.90	<.001
SEER S‐PS region, n = 1931
Surgery
No		Reference
Yes	0.57	0.50, 0.66	<.001
Diagnosis year
1990‐1998		Reference
1999‐2004	0.74	0.63, 0.87	<.001
2005‐2011	0.57	0.49, 0.66	<.001
Age, y
≥70		Reference
<70	0.72	0.62, 0.84	<.001
Chemotherapy
No		Reference
Yes	0.91	0.78, 1.05	.199
Radiation therapy
No		Reference
Yes	1.05	0.92, 1.19	.505
Hormone receptor status
Negative		Reference
Positive	0.43	0.37, 0.51	<.001
Race
Nonwhite		Reference
White	0.86	0.71, 1.05	.135
SEER 9 without the S‐PS region, n = 12,121
Surgery
No		Reference
Yes	0.58	0.55, 0.61	<.001
Diagnosis year
1990‐1998		Reference
1999‐2004	0.85	0.80, 0.91	<.001
2005‐2011	0.72	0.67, 0.76	<.001
Age, y
≥70		Reference
<70	0.77	0.73, 0.82	<.001
Chemotherapy
No		Reference
Yes	0.91	0.86, 0.97	.002
Radiation therapy
No		Reference
Yes	1.02	0.97, 1.07	.525
Hormone receptor status
Negative		Reference
Positive	0.47	0.44, 0.50	<.001
Race
Nonwhite		Reference
White	0.84	0.79, 0.89	<.001

Abbreviations: HzR, hazard ratio; SEER 9, Surveillance, Epidemiology, and End Results 9 registries; S‐PS, Seattle‐Puget Sound.