Table 2 Univariate and multivariate Cox regression models of factors associated with OS

Gender

 Female

reference

reference

 Male

0.72

0.57–0.91

0.0064

0.86

0.68–1.10

0.228

Age

 ≤65

reference

reference

 >65

1.49

1.16–1.91

0.0015

1.30

1.01–1.68

0.045

Race

 Non-Hispanic White

reference

 Hispanic White

1.21

0.89–1.66

0.23

 Black

1.10

0.68–1.80

0.69

 Others

0.98

0.71–1.34

0.89

T stage

 T1/2

reference

 T3

1.31

0.73–2.36

0.36

 T4

1.41

0.82–2.44

0.21

N stage

 N0

reference

 N1

0.91

0.69–1.19

0.47

Tumor Diameter

 ≤6 cm

reference

reference

 >6 cm

1.62

1.27–2.07

0.0001

1.19

1.09–1.29

< 0.0001

Tumor Extension

 Limited to Thyroid

reference

 Extrathyroidal Extension

0.96

0.71–1.29

0.8

Distant Lymph Node Metastasis

 No

reference

 Yes

1.12

0.87–1.44

0.37

Bone Metastasis

 No

reference

 Yes

0.85

0.64–1.13

0.27

Brain Metastasis

 No

reference

 Yes

1.06

0.65–1.73

0.82

Liver Metastasis

 No

reference

 Yes

0.95

0.62–1.45

0.8

Lung Metastasis

 No

reference

reference

 Yes

1.54

1.11–2.15

0.01

1.55

1.10–2.17

0.011

Multiple Organ Metastases

 No

reference

 Yes

1.10

0.83–1.46

0.5

Marital status

 Single (never married)

reference

 Married

0.89

0.62–1.28

0.54

 Divorced/Separated/Widowed

1.30

0.87–1.94

0.21

 Unknown

0.88

0.27–2.90

0.83

Surgery to Primary Site

 No

reference

reference

 Non-thyroidectomy

0.64

0.44–0.94

0.02

0.73

0.50–1.07

0.108

 Thyroidectomy

0.51

0.38–0.67

< 0.0001

0.59

0.44–0.79

< 0.0001

Radiotherapy

 No

reference

reference

 Yes

0.60

0.48–0.77

< 0.0001

0.70

0.54–0.91

0.007

Chemotherapy

 No

reference

reference

 Yes

0.39

0.30–0.50

< 0.0001

0.54

0.42–0.70

< 0.0001