PD-L1 expression level in different thymoma stages and thymic carcinoma: a meta-analysis

Tumori. 2020 Aug;106(4):306-311. doi: 10.1177/0300891620915788. Epub 2020 May 5.

Abstract

Background: The immune checkpoint ligand, programmed cell death 1 ligand 1 (PD-L1), is expressed in various tumors and associated with response to drugs that target programmed cell death protein 1. Previous studies have estimated the level of PD-L1 expression among different stages of thymoma and thymic carcinoma to evaluate its potential use as a diagnostic factor; however, its varying expression level has been problematic. We conducted this meta-analysis of published literature to evaluate PD-L1 expression in thymomas and thymic carcinomas.

Methods: We analyzed 12 studies that included 320 patients with type A/AB/B1 thymoma, 225 patients with type B2/B3 thymoma, and 180 patients with thymic carcinoma.

Results: No difference in PD-L1 expression level was found between the B2/B3 vs C groups (odds ratio [OR], 0.67; 95% confidence interval [CI], 0.26, 1.76; p = 0.42). However, the heterogeneity was very high (I2 = 78%), and a significant difference was found between groups A/AB/B1 and B2/B3 (OR, 0.22; 95% CI, 0.12, 0.41; p < 0.001), with a relatively low heterogeneity (I2 = 55%).

Conclusion: PD-L1 positivity might be a useful factor to differentiate type A/AB/B1 thymoma from type B2/B3 and thymic carcinoma. This result might be valuable for potential anti PD-L1 treatment in thymoma and thymic carcinoma.

Keywords: PD-L1; PD-L1 expression; Thymoma; diagnosis; meta-analysis; thymic carcinoma.

Publication types

  • Meta-Analysis

MeSH terms

  • Adult
  • Aged
  • B7-H1 Antigen / antagonists & inhibitors
  • B7-H1 Antigen / genetics*
  • Biomarkers, Tumor / genetics
  • Female
  • Gene Expression Regulation, Neoplastic / genetics
  • Humans
  • Male
  • Middle Aged
  • Neoplasm Staging
  • Programmed Cell Death 1 Receptor / genetics
  • Programmed Cell Death 1 Receptor / immunology
  • Thymoma / genetics*
  • Thymoma / immunology
  • Thymoma / pathology
  • Thymoma / therapy
  • Thymus Neoplasms / genetics*
  • Thymus Neoplasms / immunology
  • Thymus Neoplasms / therapy

Substances

  • B7-H1 Antigen
  • Biomarkers, Tumor
  • CD274 protein, human
  • PDCD1 protein, human
  • Programmed Cell Death 1 Receptor