Table 2.

Univariate and multivariate Cox proportional hazards regression analyses for overall survival.

Variable	Univariate		Multivariate adjusted*
	HR (95% CI)	p-value	HR (95% CI)	p-value
Treatment type
Non-RT and non-surgery	Ref		Ref
RT	0.68 (0.58–0.79)	<0.001	0.77 (0.66–0.89)	<0.001
Surgery	0.31 (0.30–0.33)	<0.001	0.52 (0.48–0.56)	<0.001
RT and surgery	0.27 (0.25–0.29)	<0.001	0.42 (0.38–0.46)	<0.001
Age
<70	Ref		Ref
≥70	1.33 (1.27–1.40)	<0.001	1.42 (1.35–1.49)	<0.001
Sex
Female	Ref		Ref
Male	1.04 (0.99–1.10)	0.126	1.10 (1.04–1.16)	<0.001
Year of diagnosis
2004–2009	Ref		Ref
2010–2015	0.96 (0.91–1.00)	0.069	0.95 (0.90–1.00)	0.047
Marital status
Married	Ref		Ref
Others	1.16 (1.10–1.21)	<0.001	1.18 (1.12–1.24)	<0.001
Race
White	Ref		Ref
Others	1.01 (0.95–1.07)	0.782	1.02 (0.96–1.08)	0.517
Stage
Localized	Ref		Ref
Regional	2.34 (2.18–2.50)	<0.001	2.41 (2.24–2.59)	<0.001
Distant	4.13 (3.88–4.39)	<0.001	3.66 (3.40–3.94)	<0.001
Grade
I	Ref		Ref
II	1.52 (1.39–1.67)	<0.001	1.36 (1.24–1.49)	<0.001
III	2.43 (2.22–2.67)	<0.001	1.85 (1.68–2.03)	<0.001
IV	2.51 (2.09–3.00)	<0.001	1.94 (1.61–2.33)	<0.001
Unknown	3.13 (2.85–3.44)	<0.001	1.43 (1.29–1.58)	<0.001
Tumor size
<5 cm	Ref		Ref
≥5 cm	1.76 (1.64–1.89)	<0.001	1.29 (1.20–1.39)	<0.001
Unknown	1.82 (1.72–1.92)	<0.001	1.36 (1.29–1.44)	<0.001
Chemotherapy
No/Unknown	Ref		Ref
Yes	1.17 (1.11–1.22)	<0.001	0.69 (0.65–0.74)	<0.001

HR, hazard ratio; CI, confidence interval; RT, radiotherapy; Ref, reference.

The hazard ratio (HR) and 95% confidence interval (CI) were calculated for survival status with respect to treatment status using Cox proportional hazards models. Both non-adjusted and multivariate-adjusted models were implemented.

*Adjusted for age, sex, year of diagnosis, marital status, race, stage, grade, tumor size, and chemotherapy status.