Table 2 Cox proportional hazards regression analysis for OS

 Urban

Ref

Ref

Ref

Ref

Ref

Ref

 Country

1.221

1.0212–1.4598

0.0293

1.0272

0.8533–1.2364

0.7779

Ages (years)

NI

 < 60

Ref

Ref

Ref

 60–69

0.9238

0.7541–1.1316

0.4461

 ≥ 70

1.0349

0.8269–1.2952

0.08909

Sex

NI

 Female

Ref

Ref

Ref

 Male

0.883

0.7374–1.0573

0.1781

BMI (Kg/m²)

NI

 < 28

Ref

Ref

Ref

 ≥ 28

1.1157

0.8557–1.4548

0.4211

 Unknown

0.4844

0.2595–0.9043

0.0236

Smoking history

NI

 No

Ref

Ref

Ref

 Yes

1.0663

0.8604–1.3215

0.5596

 Fundus

Ref

Ref

Ref

Ref

Ref

Ref

 Body

1.5472

1.2442–1.9241

0.0001

1.4901

1.1858–1.8726

0.0007

 Neck

1.4257

1.0976–1.8519

0.0082

1.1776

0.8959–1.5479

0.2437

 Unknown

1.445

0.9751–2.1412

0.068

0.6761

0.4434–1.0310

0.0705

 I

Ref

Ref

Ref

Ref

Ref

Ref

 II

2.9912

1.1632–7.6921

0.0237

2.9253

1.1281–7.5861

0.0281

 III

7.3437

3.0318–17.7882

< 0.0001

6.4359

2.6198–15.8108

0.0001

 IV

16.4044

6.7898–39.6340

< 0.0001

10.4364

4.1505–26.2422

< 0.0001

T stage

NI

 T1

Ref

Ref

Ref

 T2

2.2162

0.9901–4.9607

0.0541

 T3

5.6811

2.6900–11.9979

< 0.0001

 T4

9.2513

4.3199–19.8121

< 0.0001

 Unknown

12.0606

5.5666–26.1303

< 0.0001

N stage

NI

 N0

Ref

Ref

Ref

 N1

2.4167

1.7968–3.2505

0.017

 N2

4.2985

3.2423–5.6989

<  0.0001

 Unknown

3.1367

2.5164–3.9099

< 0.0001

M stage

NI

 M0

Ref

Ref

Ref

 M1

2.4876

2.0433–3.0286

< 0.0001

 Unknown

1.4786

1.0065–2.1721

0.0474

 Well-differentiated

Ref

Ref

Ref

Ref

Ref

Ref

 Moderately differentiated

1.4133

0.7651–2.6107

0.2717

1.3022

0.6944–2.4420

0.4128

 Poorly differentiated

2.3874

1.3269–4.2957

0.0039

1.7171

0.9330–3.1604

0.0839

 Unknown

2.4023

1.3517–4.2694

0.003

1.5552

0.8560–2.8257

0.1493

 < 27 U/mL

Ref

Ref

Ref

Ref

Ref

Ref

 ≥ 27 U/mL

2.2785

1.8655–2.7830

< 0.0001

1.3941

1.0838–1.7933

0.0101

 Unknown

1.3304

0.9374–1.8881

0.1118

1.2309

0.6981–2.1705

0.475

 < 20 IU/mL

Ref

Ref

Ref

Ref

Ref

Ref

 ≥ 20 IU/mL

1.9779

1.6322–2.3969

< 0.0001

1.1169

0.8790–1.4192

0.3679

 Unknown

1.042

0.7776–1.3964

0.7838

1.0146

0.6312–1.6310

0.9525

With chronic disease

NI

 No

Ref

Ref

Ref

 Yes

0.8733

0.7292–1.0460

0.1432

Gallstone

NI

 No

Ref

Ref

Ref

 Yes

0.9403

0.7885–1.1213

0.4955

Adjuvant therapy

NI

 None

Ref

Ref

Ref

 Received

0.8719

0.7105–1.0699

0.1916

 Simple resection

Ref

Ref

Ref

Ref

Ref

Ref

 Radical resection

1.3679

1.0384–1.8021

0.0267

1.0397

0.7820–1.3823

0.7898

 Palliative surgery

3.3214

2.5191–4.3792

< 0.0001

1.41

0.9886–2.0111

0.0592