Table 2.

Univariate and multivariate analyses of variables associated with OS

Characteristics	Univariate analysis		Multivariable analysis
	HR (95% CI)	P-value	HR (95% CI)	P-value
Marital status
Married	Reference
Unmarried	0.817 (0.591–1.131)	0.224
Sex
Male	Reference
Female	0.753 (0.543–1.046)	0.090
Age at diagnosis		<0.001		<0.001
0–39	Reference		Reference
40–59	1.534 (1.054–2.235)	0.026	2.153 (1.390–3.335)	0.001
60–89	3.952 (2.533–6.167)	<0.001	6.332 (3.801–10.549)	<0.001
Year of diagnosis		<0.001		<0.001
1973–1987	Reference		Reference
1988–2001	0.627 (0.370–1.063)	0.082	0.667 (0.371–1.198)	0.175
2002–2015	0.234 (0.144–0.380)	<0.001	0.163 (0.078–0.340)	<0.001
Laterality
Right	Reference
Left	0.971 (0.704–1.340)	0.859
Histologic grade		0.002		0.035
Grade I+II	Reference		Reference
Grade III+IV	2.812 (1.437–5.502)	0.003	2.318 (1.071–5.019)	0.033
Unknown	2.520 (1.480–4.290)	0.001	2.222 (1.199–4.117)	0.011
Ethnicity		0.827
White	Reference
Black	1.151 (0.614–2.161)	0.661
Others	1.151 (0.637–2.081)	0.641
Historic stage		<0.001		<0.001
Localized	Reference		Reference
Regional	1.853 (1.054–0.258)	0.032	2.271 (1.228–4.198)	0.009
Distant	16.083 (6.302–41.041)	<0.001	13.493 (5.092–35.754)	<0.001
Unknown	0.863 (0.593–1.256)	0.441	2.145 (1.099–4.187)	0.025
Radiation therapy
Yes	Reference
No/unknown	1.007 (0.654–1.552)	0.973
Chemotherapy
Yes	Reference		Reference
No/unknown	0.651 (0.458–0.925)	0.017	0.478 (0.310–0.736)	0.001
Surgery of primary site		0.009		0.099
Yes	Reference
No	3.806 (2.057,7.043)	<0.001	1.987 (1.033,3.822)	0.040
Unknown	3.664 (2.562,5.239)	<0.001	1.336 (0.642,2.776)	0.438

Abbreviations: HR, hazard ratio; OS, overall survival.