Table 3. Literature scored using the Cochrane Risk of Bias 2.0 scale.

Include the literature	Year of publication	Random selection bias	Allocation selection bias	Performance bias	Detection bias	Attrition bias	Reporting bias	Other bias
Cloughesy TF	2019	①	①	③	②	①	③	①
Zhao J	2019	①	①	①	②	③	①	①
Nduom EK	2016	①	③	①	①	①	①	③
Schalper KA	2019	③	③	①	①	①	③	②
Du Four S	2016	③	③	①	②	①	③	①
Jan CI	2018	①	③	①	①	②	①	③

, low risk; ②, unclear risk; ③, high risk.