Variable

No. studies

Model

OR (95% CI)

Heterogeneity

Begg’s test

Egger’s test

I2 (%)

P-value (Q-test)

Gendera

14

Fixed

1.12 (0.91, 1.37)

12.9

0.312

0.661

0.285

Tumor sizeb

8

Fixed

1.11 (0.82, 1.49)

39.6

0.115

0.902

0.139

TNM stagec

12

Random

2.68 (1.61, 4.48)

78.4

0.000

0.086

0.160

Invasion depthd

8

Random

2.05 (1.32, 3.19)

54.0

0.033

0.174

0.500

Lymph node metastasise

14

Random

1.95 (1.29, 2.96)

71.8

0.000

0.443

0.847

Degree of differentiationf

11

Random

1.17 (0.63, 2.16)

82.3

0.000

0.436

0.521