Data Extraction and Quality Assessment
Articles were screened independently by two researchers (RT and RM) (according to Flowchart 1) and disagreements resolved through discussions with other researchers. The extracted information included author’s first name, study location, study type, type of marker investigated, year of publication, type of survival analysis performed, mean follow-up period, sample size, and a summary of the cut-off points for the markers investigated. OS is usually the time length from the beginning of medical treatment until outcome occurrence (death whether or end of the follow-up period of the patient). PFS is the duration when the treatment is started until tumor progresses or death happens for any reason. In order to evaluate quality of the articles, two researchers (MR and AH) independently used the checklist of Newcastle Ottawa Scale (NOS) (35). The articles with a total score of ≥7 were considered as high-quality.