2.2 Study selection and inclusion criteria
In this systematic review, original studies were selected when conformed to the established inclusion criteria, as further stated subsequently: (1) Publications using English language. (2) Data not received on animal samples. (3) Observational studies. (4) Reports focusing on the evaluation of PD-L1 in clinicopathological parameters and survival outcomes. (5) Studies supplying existing odds ratio (OR) or hazard ratio (HR) along with 95% CI , or else, adequate data to calculated. (6) Participants not undergoing any radiotherapy/chemotherapy before surgical resection.
Two researchers were responsible for independently screening titles and abstracts, and then deeply evaluated the retrieved articles in the primal search. The articles were discarded that were performed in nonhuman subjects, editorials, duplicates, expert comments, review in various forms, meta-analysis, clinical trials.