PD-L1 Expression in Esophageal Squamous Cell Carcinoma: A Comparative Analysis of 3 Different Antibodies

Abstract

Background: Several studies have assessed the comparability of various immunohistochemical assays for programmed cell death 1 ligand 1 (PD-L1) expression in different kinds of tumours. However, there is a lack of relevant research on the detection efficacy of different PD-L1 clones in esophageal squamous cell carcinoma (ESCC). This study was performed to compare the PD-L1 expression results of three PD-L1 antibodies to assess their effectiveness.Methods: Three hundred and twenty-four cases of ESCC tissues in our medical institution were used to prepare tissue microarrays (TMAs). TMAs were stained with three validated assays (Ventana’s SP263 and Dako’s 28-8 and 22C3). Then, pathologists scored each tissue according to PD-L1 staining.Results: We found very high concordance when comparing 28-8 with SP263 at both the 1% (95.7%) and 50% (99.1%) cutoffs. Low overall concordance was found between 28-8 and 22C3 at the 1% cutoff (85.5%). Moreover, sensitivities of 91.2% and 87.5% were found for 28-8 compared with SP263 at the 1% and 50% cutoffs, respectively. Sensitivities of only 75.6% and 50% were found for 28-8 compared with 22C3 at the 1% and 50% cutoffs, respectively, which may result in more false negatives.Conclusions: We demonstrate that the PD-L1 SP263 shows high levels of overall agreement with 28-8 and relatively high sensitivity, with a low false negative rate. Thus, SP263 seems to be a reliable assay for PD-L1 testing in ESCC when considering pembrolizumab as immunotherapy.