Abstract Background: Esophageal cancer (ESCC) remains a highly lethal disease due to late diagnosis and limited responsiveness to conventional therapies. Recent studies have highlighted the role of immune checkpoint pathways in its pathogenesis, particularly the PD-1/PD-L1 interaction, which enables tumor cells to escape immune surveillance. We have developed a PD-L1 CAL10 assay for immunohistochemical (IHC) detection of PD-L1 in ESCC specimens. Here, we have compared this novel PD-L1 CAL10 assay for IHC detection of PD-L1 in ESCC specimens with two common research-utilized PD-L1 IHC assays. Design: The primary objective was to compare the PD-L1 CAL10 assay with other commercially available assays, SP263 and 22C3, at ≥1% tumor proportion score (TPS) and ≥50% TPS cutoffs. Also, we measured interobserver/interpathologist agreement (secondary objective) for each assay type at ≥1% TPS and ≥50% TPS cutoffs. Seventy (70) whole tissue formalin fixed paraffin embedded (FFPE) unique ESCC cases were included in the study. Each case was serially sectioned at 4 µm. Each of these sections was stained with H OPA, Overall percent agreement ). Additionally, its scoring pattern was similar to the other two PD-L1 clones. Conclusion: The initial results suggest that the PD-L1 CAL10 assay is comparable to the other tested PD-L1 assays for ESCC specimens and can be a suitable option for further translational research evaluations. Citation Format: Ibrahim Abukhiran, Matthew G. Hanna, Dimitrios Korentzelos, Rajiv Dhir, Aatur D. Singhi, Shubham Dayal, Joseph Chiweshe, Xiaozhi Zhou, Robert Monroe, Michelle Wood-Trageser. Performance analysis of a novel PD-L1 CAL10 assay in esophageal cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 7912.
Abukhiran et al. (Fri,) studied this question.