To further evaluate the prognostic significance of mTOR and p-mTOR in detail, all of six included studies addressing on the relationship between mTOR/p-mTOR expression and OS of ESCC cases were stratified into several subgroups according to the statistical analysis methods, cut-off values, follow-up periods and positive-staining sites [40, 41, 43–46]. Here, MTOR is linked to esophageal squamous cell carcinoma.