Table 7 Summary of meta-analysis results and evidence quality

1. Patient characteristic

 1.1 Age

6

1584

1.06 [0.90, 1.25]

0.47

36%

-

Class II

 1.2 Male

17

4146

0.94 [0.86, 1.03]

0.16

24%

0.185

Class I

 1.3 Elevated CEA

9

2417

1.56 [1.19, 2.04]

0.001

81%

-

Class II

 1.4 Elevated CA199

4

1138

1.48 [1.20, 1.81]

 < 0.001

36%

-

Class II

2. Primary tumor characteristics

 2.1 Poor

differentiation

6

1362

1.13 [1.03, 1.25]

0.01

0%

-

Class I

 2.2 Lymph node

metastasis

19

4471

1.31 [1.17, 1.48]

 < 0.001

47%

0.035

Class II

 2.3 T3-4

10

2558

1.04 [0.93, 1.17]

0.48

0%

0.623

Class I

 2.4 Rectal tumor

17

3959

1.00 [0.91, 1.11]

0.93

41%

0.897

Class I

3. Liver metastases characteristics

 3.1 Synchronous

metastases

16

3702

1.23 [0.89, 1.71]

0.21

90%

0.121

Class III

 3.2 More

metastases

13

3254

1.46 [1.26, 1.68]

 < 0.001

57%

0.206

Class II

 3.3 Larger

metastases

7

1862

1.18 [1.04, 1.34]

0.01

29%

-

Class I

 3.4 Bilobar

distribution

13

2717

1.37 [1.21, 1.55]

 < 0.001

40%

0.811

Class I

 3.5 Extrahepatic

metastases

4

1332

1.13 [0.99, 1.29]

0.06

25%

-

Class I

4. Surgical procedures and operative outcome

 4.1 Laparoscopic

resection

3

855

0.87 [0.72, 1.05]

0.16

0%

-

Class II

 4.2 Simultaneous

resection

8

2161

1.00 [0.83, 1.21]

0.98

55%

-

Class II

 4.3 Major

hepatectomy

12

2588

1.16 [1.07, 1.25]

 < 0.001

0%

0.329

Class I

 4.4 Positive

surgical margin

12

3187

1.33 [1.20, 1.48]

 < 0.001

34%

0.505

Class I

 4.5 Preoperative

chemotherapy

12

2606

1.12 [0.97, 1.28]

0.12

58%

0.074

Class III

 4.6 Postoperative

chemotherapy

12

3200

0.93 [0.78, 1.11]

0.40

74%

0.616

Class II

 4.7 Blood

transfusion

9

2319

1.10 [0.96, 1.25]

0.16

39%

-

Class I

 4.8 Postoperative

complications

6

1731

1.28 [1.13, 1.44]

 < 0.001

30%

-

Class I