Table 2 Effect size and subgroup analyses for MSC administration in preclinical studies of solid tumor metastasis incidence

All experiments

100.0

2.04

1.57, 2.65

21

Cancer type

 Breast cancer

45.8

1.94

1.43, 2.62

0

0.630

0

 Other cancer

54.2

2.22

1.41, 3.50

21

Animal species/strain

 Nude mice

86.2

2.03

1.53, 2.68

19

0.810

0

 Other mice/rat

13.8

2.30

0.85, 6.22

54

Source of MSC

 Human bone marrow

65.1

1.81

1.24, 2.64

42

0.450

0

 Other human tissue

16.1

2.77

1.61, 4.77

0

 Mice/rat bone marrow

18.8

2.09

1.24, 3.51

0

Metastasis estimation

 Fluorescence microscopy

17.2

2.95

1.32, 6.60

27

0.610

0

 Histological evaluation

34.6

1.79

1.03, 3.14

38

 Bioluminescence

48.2

2.13

1.59, 2.84

0

Cancer cell/MSC dose ratio

 = 1

47.2

1.39

0.9, 2.16

38

0.030

71.6

 > 1

45.3

2.62

1.89, 3.65

0

 < 1

7.5

3.83

1.68, 8.73

0

Timing of MSC administration

 Co-administration

73.6

2.19

1.72, 2.79

0

0.240

28.5

 Follow-administration

26.4

1.39

0.68, 2.84

48

Study length (days)

 ≤ 42

100

2.04

1.57,2.65

21

–

–

 > 42

0

–

–

–

Metastasis site

 Lung

55.4

1.61

1.08, 2.40

34

0.060

72

 Other tissue

44.6

2.64

1.92, 3.63

0

Study quality category

 Meet 9–12 criteria

0

–

–

–

0.630

0

 Meet 5–8 criteria

9.2

2.90

0.74, 11.40

37

 Meet 0–4 criteria

90.8

2.06

1.56, 2.71

21

Impact factor of journal

≤ 5

49.3

1.90

1.19, 3.01

36%

0.580

0

> 5

50.7

2.21

1.66, 2.95

0