PD-L1 immunohistochemistry in gastric cancer: Comparison of combined positive score and tumor area positivity across 28-8, 22C3, and SP263 assays.

• DOI: 10.1200/jco.2024.42.16_suppl.2625
• Publication Date: 2024-06-14T20:18:01Z
• Authors: Samuel J. Klempner; Eric S Cowden; Samuel Louis Cytryn; Matteo Fassan; Hisato Kawakami; Hideaki Shimada; Laura H. Tang; Daniel-Christoph ...; Yasushi Yatabe; Alexander Savchenko; Jennifer Salcius; Dorhyun Johng; Lauren Fairchild; Jing Chen; Giuliana Montenegro; Markus H. Moehler
• Keywords: 03 medical and health sciences; 0302 clinical medicine

2625 Background: The clinical application of programmed death-ligand 1 (PD-L1) immunohistochemistry is complicated by multiple available assays and different testing platforms, scoring algorithms, cut-offs applied. This study assessed the analytical comparability three commercially PD-L1 (28-8, 22C3, SP263) two algorithms used in gastric cancer (GC). Methods: Serial sections 100 procured GC samples, selected 28-8 assay to represent dynamic range expression, were stained with vitrodiagnostic (IVD)-grade assays. Stained slides blindly independently evaluated trained pathologists for intra- inter-reader assessment. Scoring was performed using combined positive score (CPS) tumor area positivity (TAP) methods, followed statistical analysis. Digital image analysis (DIA) objectively assess technical performance each simulating CPS TAP methods HALO platform. Results: Comparable, specific, staining patterns observed Pathologist assessment reproducible sample cohorts despite discernible variability intensity. When same applied, inter- intra-assay assessments all assays, either or demonstrated moderate almost-perfect (inter-assay Cohen’s kappa [κ] ranged from 0.47 0.83) substantial (intra-assay κ 0.77 1.00) agreement, respectively. Moreover, inter-pathologist evaluation showed a significant level reproducibility (intraclass correlation coefficient (ICC) ≥0.92). DIA confirmed no difference when specific digital Conclusions: highlights concordance among major are prospectively Independently, further supports These observations support flexibility cross-application currently characterize PD-L1–positive samples.