title: Prognostic role of PD-L1 in malignant solid tumors: a meta-analysis.
abstract: OBJECTIVE
  The aim of this study was to elucidate the rates and prognostic roles of programmed cell death ligand 1 (PD-L1) immunohistochemical (IHC) expression in various malignant tumors through a systematic review and meta-analysis.
  
  
  METHODS
  The current study included 16,176 patients from 97 eligible studies. We investigated PD-L1 expression and its correlation with survival rate in various malignant tumors.
  
  
  RESULTS
  The estimated rate of PD-L1 IHC expression was 0.449 (95% confidence interval [CI] 0.404-0.495). The highest and lowest PD-L1 expression levels were found in thyroid cancer (0.829, 95% CI 0.781-0.868) and small-cell neuroendocrine carcinoma (0.005, 95% CI 0.000-0.080), respectively. PD-L1 expression was significantly correlated with poorer overall survival and disease-free survival rates (hazard ratios 1.276, 95% CI 1.097-1.486 and 1.304, 95% CI 1.034-1.644, respectively). However, PD-L1 IHC expression was significantly correlated with worse overall survival rates in patients with esophageal cancer and renal cell carcinoma and with worse disease-free survival rates in patients with colorectal cancer, hepatocellular carcinoma, and renal cell carcinoma.
  
  
  CONCLUSIONS
  Our results show that PD-L1 expression rates and the correlations with survival varied between tumor types. Detailed evaluation criteria for PD-L1 will have to be standardized before application to specific tumor types.
authors.affiliation: Department of Pathology, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul - Republic of Korea.|Current affiliation: Department of Pathology, Eulji University Hospital, Daejeon, Republic of Korea.
authors.forename: Jung-Soo
authors.initials: JS
authors.lastname: Pyo
authors.affiliation: Department of Pathology, Inje University Sanggye Paik Hospital, Seoul - Republic of Korea.
authors.forename: Guhyun
authors.initials: G
authors.lastname: Kang
authors.affiliation: Department of Pathology, Inje University Sanggye Paik Hospital, Seoul - Republic of Korea.
authors.forename: Jung Yeon
authors.initials: JY
authors.lastname: Kim
mesh_terms: D060890:B7-H1 Antigen / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000378:metabolism*; D006801:Humans; D007124:Immunoenzyme Techniques; D009369:Neoplasms / Q000378:metabolism* / Q000473:pathology*; D011379:Prognosis; D015996:Survival Rate
chemical_list: D060890:B7-H1 Antigen; D014408:Biomarkers, Tumor; C423236:CD274 protein, human