Table 2.

The Newcastle-Ottawa Quality Assessment Scale for included controlled studies.

Study	Selection of the study groups	Comparability of the groups	Outcome	Total score
Mayer et al. 2015 [4]	⭐⭐⭐⭐	⭐	⭐⭐	7
Pfeiffer et al. 2020 [15]	⭐⭐⭐⭐	⭐	⭐⭐	7
Sueda et al. 2016 [16]	⭐⭐⭐⭐	⭐	⭐⭐	7
Masuishi et al. 2017 [17]	⭐⭐⭐⭐	⭐	⭐⭐	7
Makiyama et al. 2018 [18]	⭐⭐⭐⭐	⭐	⭐⭐	7
Yoshino et al. 2012 [5]	⭐⭐⭐⭐	⭐	⭐⭐	7
Cutsem et al. 2017 [9]	⭐⭐⭐⭐	⭐	⭐⭐	7
Xu et al. 2017 [10]	⭐⭐⭐⭐	⭐⭐	⭐⭐	8
Longo-Muñoz et al. 2016 [19]	⭐⭐⭐⭐	⭐⭐	⭐⭐	8
Moriwaki et al. 2018 [20]	⭐⭐⭐⭐	⭐⭐	⭐⭐	8
Kotani et al. 2019 [21]	⭐⭐⭐⭐	⭐⭐	⭐⭐	8
Fujii et al. 2020 [11]	⭐⭐⭐⭐	⭐	⭐⭐	7
Ogata et al. 2020 [22]	⭐⭐⭐⭐	⭐	⭐⭐	7
Nose et al. 2020 [23]	⭐⭐⭐⭐	⭐⭐	⭐⭐	8