Table 3.
ROBINS-I analysis to assess the risk of bias in each included study
| Bias due to confounding | Bias in selection of participants into the study | Bias in classification of intervention | Bias due to deviations from intended interventions | Bias due to missing data | Bias in measurement of outcomes | Bias in selection of the reported result | Overall risk of bias | |
|---|---|---|---|---|---|---|---|---|
| Ali 2017 | 2 | 1 | 1 | 1 | 1 | 1 | 2 | Moderate |
| Bowden 2019 | 2 | 1 | 1 | 1 | 1 | 1 | 2 | Moderate |
| Chang 2010 | 2 | 1 | 1 | 1 | 1 | 1 | 2 | Moderate |
| Erlich 2019 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | Moderate |
| Izard 2019 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | Moderate |
| Kim 2008 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | Moderate |
| Minniti 2020 | 2 | 2 | 1 | 1 | 1 | 1 | 1 | Moderate |
| Mizuno 2019 | 3 | 1 | 1 | 1 | 1 | 1 | 1 | Serious |
| Nakazaki 2013 | 3 | 2 | 1 | 1 | 1 | 1 | 1 | Serious |
| Raldow 2013 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | Moderate |
| Rava 2013 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | Moderate |
| Serizawa 2006 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | Moderate |
| Susko 2020 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | Moderate |
| Suzuki 2000 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | Serious |
| Yamamoto 2021 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | Moderate |
0 = no information/unclear, 1=“Low risk”, 2=“Moderate risk”, 3=“Serious risk”, 4=“Critical risk” of bias. The quality of evidence for assessing overall survival in patients with 10 or more BMs is shown in Table 4. The quality of evidence was downgraded to very low as per the GRADE criteria due to limitations in study design and the risk of bias, particularly in the largest studies included for analysis