Table 2:

Methodological quality of included trials

Name	SPCG-4	PIVOT	VACURG
Randomization allocation (SB)	Adequate	Adequate	Unclear risk
Allocation concealment (SB)	Adequate	Adequate	Unclear risk
Blinding of outcome assessment (SB)	Adequate	Adequate	Unclear risk
Incomplete outcome data (AB)	Adequate	Adequate	Inadequate₳
Selective report(RB)	Adequate	Adequate	Unclear risk
Other bias₢	Adequate	Adequate	Inadequate₳
Sample power	85% power to detect a 25% relative reduction in all-cause mortality	85% power to detect a 25% relative reduction in all-cause mortality	NM
Analysis approach	Intention-to-treatment	Intention-to-treatment	NM
Randomization strategies	A telephone service at office outside the clinical units	Central interactive telephone system	NM
Stratification in randomization	According to degree of differentiation in cancer grade and center	According to sites	NM
Funding source	No industry	No industry	No industry

^₰If no notable bias exist which effect on results of trial/

^₳if there was a great bias which make misleading on results of trial/

^₫if no sufficient data reported to assess the studies/

NM: not mention in trial’s reports/

SB: selection bias/

AB: attrition bias/

RB: reporting bias/

^₢some biases that did not include in the category