Table 2. Study quality and bias in the retrospective cohort studies according to the Newcastle-Ottawa Scale (NOS) checklist.

Datasets	Total score	Cohort selection				Comparability			Outcome
		Representativeness of the Exposed Cohort	Selection of the Non-Exposed Cohort	Ascertainment of Exposure	Demonstration that the outcome of interest was not present at study initiation	Comparability of cohorts based on the design or analysis	Assessment of outcome	Was follow-up long enough for outcomes to occur	Adequacy of the follow-up of cohorts
GSE3141	7	*	*	*	*		*	*	*
GSE8894	8	*	*	*	*	*	*	*	*
GSE13213	9	*	*	*	*	**	*	*	*
GSE14814	8	*	*	*	*	*	*	*	*
GSE26939	8	*	*	*	*	*	*	*	*
GSE29013	8	*	*	*	*	*	*	*	*
GSE30219	8	*	*	*	*	*	*	*	*
GSE31210	9	*	*	*	*	**	*	*	*
GSE37745	8	*	*	*	*	*	*	*	*
GSE41271	8	*	*	*	*	*	*	*	*
GSE42127	9	*	*	*	*	**	*	*	*
GSE50081	9	*	*	*	*	**	*	*	*
GSE68465	8	*	*	*	*	*	*	*	*
GSE72094	8	*	*	*	*	*	*	*	*
GSE83227	8	*	*	*	*	*	*	*	*
TCGA	8	*	*	*	*	*	*	*	*