Table 4 Effect size and subgroup analyses for MSC administration in preclinical studies of breast cancer metastasis number

All experiments

100.0

2.04

0.87, 3.21

90

Animal species/strain

 Nude mice

100

2.04

0.87, 3.21

90

–

–

 Other mice/rat

0

–

–

–

Source of MSC

 Human bone marrow

40.3

4.06

2.43, 5.70

70

0.006

75.8

 Other human tissue

30

− 0.07

− 2.54, 2.41

95

 Mice/rat bone marrow

14.8

1.04

0.24, 1.83

0

 Unclear

14.9

1.20

− 0.73, 3.14

82

Metastasis estimation

 Fluorescence microscopy

64.1

1.22

− 0.2, 2.65

90

0.07

70.5

 Histological evaluation

35.9

2.92

1.82, 4.02

55

 Bioluminescence

0

–

–

–

Cancer cell/MSC dose ratio

 = 1

58.8

1.48

− 0.14, 3.1

92

0.35

0

 > 1

0

–

–

–

 < 1

41.2

2.44

1.27, 3.62

65

Timing of MSC administration

 Co-administration

84.8

2.38

1.54, 3.22

72

0.001

98

 Follow-administration

15.2

− 2.24

− 2.93, 1.55

0

Study length (days)

 ≤ 42

44.8

0.29

− 1.42, 2.00

93

0.008

85.7

 > 42

55.2

3.24

1.88, 4.6

78

Metastasis site

 Lung

75.6

1.80

0.47, 3.12

90

0.680

0

 Other tissue

24.4

2.20

0.84, 3.56

60

Impact factor of journal

 ≤ 5

30

− 0.64

− 2.52, 1.23

92

0.002

90

 > 5

70

2.8

1.78, 3.82

73