Abstract 2180: The PD-L1 protein expression in Chinese patients with advanced esophageal cancers: a multi-center retrospective study

Introduction: Programmed cell death ligand-1 (PD-L1) is the ligand of programmed cell death-1 (PD-1), a member of the immunoglobulin gene superfamily that plays a role in programmed cell death. Accumulating evidence of anti-PD-1 therapy has showed improved survival benefit for esophageal cancer (EC) patients. PD-L1 has emerged as a crucial predictor for efficacy of immunotherapy. However, the understanding of PD-L1 as a biomarker is complicated by various immunohistochemistry platforms, PD-L1 antibodies, scoring systems, and cut-offs for immunotherapy. Although PD-L1 expression has been widely investigated, the real-world PD-L1 expression status in Chinese patients with advanced EC nationwide with unified testing platform, antibody, scoring system and cut-off is largely unrevealed. Methods: The present study was a nationwide multi-center retrospective analysis of data from six centers in China from August 9, 2021, to February 28, 2022. Patients with histologically or cytologically confirmed diagnoses of advanced EC were included. The primary outcome was the prevalence of high PD-L1 expression in patients with advanced EC. Immunohistochemical analysis of PD-L1 expression was performed by using the PD-L1 IHC 22C3 pharmDx assay in EC specimens. PD-L1 protein expression was assessed by using a combined positive score (CPS). The CPS≥ 10 was defined as a high PD-L1 high expression. The Chi-square test, Fisher’s exact test, or Wilcoxon rank sum test was used to compare the PD-L1 prevalence across demographic, clinicopathologic parameters, treatment status and other biomarkers. Results: Out of 488 enrolled patients with advanced EC, 482 patients were included in the final analysis. For all testing EC patients, 207 patients (42.9% [95% CI 38.48-47.50]) were PD-L1 high expression (CPS≥10). Between the PD-L1 high (CPS≥10) group and PD-L1 low (CPS