Table 1 Baseline characteristics of the included studies for MBC

Ibrahim NK 2005 [24]

63

NM^b

NM

48.2

Mixed

Both Pre- and Post-

Metastatic

0–1

Gradishar WJ 2005 [19]

454

NM

NM

53.1

Mixed

Both Pre- and Post-

Metastatic

0- ≥ 3

Blum JL 2007 [6]

181

72

28

53

Further

Both Pre- and Post-

Metastatic

0–1

Guan ZZ 2009 [17]

210

NM

NM

50

Further

Both Pre- and Post-

Metastatic

0–1

Mirtsching B 2011 [29]

72

22

NM

63.5

First

NM

Metastatic

0–2

Gradishar WJ 2009/2012 [15, 16]

300

NM

NM

NM

First

Both Pre- and Post-

Metastatic

0–2

Brezden B 2016 [4]

123

NM

NM

NM

First

Both Pre- and Post-

Metastatic

0–2

Ranade AA 2013 [36]

195

NM

NM

NM

Mixed

NM

Metastatic

0–2

Palumbo R 2015 [35]

52

0

16

53

Further

Both Pre- and Post-

Metastatic

0–2

Fabi A 2015 [14]

42

5

8

48

Further

NM

Metastatic

0–2

Hurria A 2015 [21]

39

NM

NM

60

Mixed

NM

Metastatic

0–1

Andres FT 2015 [1]

64

0

64

51

Mixed

NM

Metastatic

0–2

Jain MM 2016 [25]

180

NM

NM

NM

Mixed

Both Pre- and Post-

Metastatic

0–2

Yamamoto S 2017 [42]

35

13

8

59

Mixed

Both Pre- and Post-

Metastatic

0–2

Tamura K 2017 [39]

197

0

36

NM

First

NM

Metastatic

0–1

Bernardo A 2017 [5]

234

0

51

58

Further

NM

Metastatic

0- ≥ 2

Gennari A 2018 [18]

255

0

NM

58

First

NM

Metastatic

0–1

Marschner N 2018 [32]

697

96

96

62.3

Mixed

NM

Metastatic

0- ≥ 2

Hurria A 2019 [23]

40

NM

10

73

Mixed

NM

Metastatic

NM

Ciruelos E 2019 [7]

60

0

NM

NM

First

NM

Metastatic

0–1

Hara F 2019 [22]

141

0

141

NM

Mixed

NM

Metastatic

0–1

Schmid P 2020 [38]

1271

0

1271

NM

First

NM

Metastatic

0–2