title: PD-L1 expression in cancer patients receiving anti PD-1/PD-L1 antibodies: A systematic review and meta-analysis.
abstract: BACKGROUND
  Despite the success of immunotherapy directed at inhibiting of programmed death-1 (PD-1)/PD-ligand (L)1 signaling, it is not established whether PD-L1 expression correlates with the clinical response and outcome in different tumors. The present meta-analysis investigates whether the PD-L1 status, detected by immunohistochemistry, is associated with clinical response and mortality in patients treated with anti-PD-1/PD-L1 therapy.
  
  
  METHODS
  A systematic literature search and quantitative analysis were planned, conducted and reported following CONSORT and QUORUM checklists, up to December 2015, to identify clinical trials with information on cancer outcome by PD-L1 immunohistochemical expression in tumor tissues. We used random effects models to estimate Summary Objective Response Rates (SORRs) and Summary Odd Ratio (SOR) for the comparison of PD-L1 positive and negative patients.
  
  
  RESULTS
  We summarized 20 trials carried out in metastatic melanoma (MM), non-small cell lung cancer (NSCLC), and renal cell carcinoma (RCC) patients receiving anti-PD-1/PD-L1 antibodies (4230 MM, 1417 NSCLC and 312 RCC patients). Positive PD-L1 MM patients showed a significant decrease (53%) in the risk of mortality vs. negative cases with no heterogeneity. Furthermore, SORRs were 45% and 27% in PD-L1 positive and negative patients, respectively, and SOR indicates a significant difference in term of responses: 2.14 (95% CI: 1.65, 2.77), with low between-study heterogeneity (I(2)=35%). Furthermore, results from randomized clinical trials on MM showed that PD-L1 expression is significantly associated with greater clinical response rates to anti-PD1 treatments (SOR 1.89; 95%CI: 1.35, 2.64) but not to other treatments (SOR 0.96; 95%CI: 0.5, 1.87). In non-squamous NSCLC SORRs were 29% and 11% in PD-L1 positive and negative patients, respectively, and SOR indicates a significant difference between responses: 3.78 (1.54, 9.24), with no between-study heterogeneity. Squamous NSCLC and RCC did not show any significant difference in response according to the PD-L1 status.
  
  
  CONCLUSIONS
  PD-L1 expression is significantly associated with mortality and clinical response to anti-PD-1/PD-L1 antibodies in MM patients and with clinical response in patients with non-squamous NSCLC.
authors.affiliation: Division of Epidemiology and Biostatistics, European Institute of Oncology, Milan, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Gandini
authors.affiliation: Division of Pathological Anatomy, Department of Surgery and Translational Medicine, University of Florence, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Massi
authors.affiliation: Unit of Medical Oncology, Department of Oncology and Hematology, Papa Giovanni XXIII Hospital, Bergamo, Italy. Electronic address: mariomandala@tin.it.
authors.forename: Mario
authors.initials: M
authors.lastname: Mandalà
mesh_terms: D000906:Antibodies / Q000627:therapeutic use*; D060890:B7-H1 Antigen / Q000276:immunology* / Q000378:metabolism*; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism / Q000628:therapy; D002292:Carcinoma, Renal Cell / Q000378:metabolism / Q000628:therapy; D006801:Humans; D007150:Immunohistochemistry; D007167:Immunotherapy / Q000379:methods; D007680:Kidney Neoplasms / Q000378:metabolism / Q000628:therapy; D008175:Lung Neoplasms / Q000378:metabolism / Q000628:therapy; D008545:Melanoma / Q000378:metabolism / Q000473:pathology / Q000628:therapy; D009362:Neoplasm Metastasis; D009369:Neoplasms / Q000378:metabolism* / Q000628:therapy*; D061026:Programmed Cell Death 1 Receptor / Q000276:immunology*
chemical_list: D000906:Antibodies; D060890:B7-H1 Antigen; C105992:PDCD1 protein, human; D061026:Programmed Cell Death 1 Receptor
keywords: Anti-PD-1/PD-L1 antibodies; Clinical trials; Melanoma; Meta-analysis; PD-L1 overexpression