Analytical and clinical comparison of three PD-L1 antibody clones using Tumor Area Positivity (TAP) and Combined Positive Score (CPS) scoring in advanced gastric cancer.

Authors

Heonwoo Lee, Hyung-Don Kim, Min-Hee Ryu, Jaewon Hyung, Ji Yong Ahn, In-Seob Lee, Jinho Shin, Young Soo Park

Published in

Gastric cancer : official journal of the International Gastric Cancer Association and the Japanese Gastric Cancer Association. Oct 27, 2026. Epub Oct 27, 2026.

Abstract

Although immune checkpoint inhibitor (ICI) plus chemotherapy is the standard first-line treatment for advanced gastric cancer (AGC), the use of different programmed cell death ligand-1 (PD-L1) antibody clones and scoring systems complicates assay interchangeability. Therefore, this study compared three PD-L1 antibody clones (SP263, 22C3, and 28 - 8) using the area-based Tumor Area Positivity (TAP) and Combined Positive Score (CPS) to evaluate their clinical implications.
Patients with AGC treated with first-line ICI plus chemotherapy or chemotherapy alone were analyzed based on PD-L1 data from identical tissue blocks. PD-L1 positivity was defined as TAP ≥ 5% and CPS ≥ 5. Interobserver agreement, inter-assay and their associations with survival were analyzed based on PD-L1 score concordance or discordance.
Across all antibody clones, TAP showed higher interobserver agreement than CPS, with SP263 demonstrating the highest reproducibility. Pairwise inter-assay concordance analysis at 5%/5 cutoff was highest between 22C3 and 28 - 8, and lowest between SP263 and 28 - 8. In patients treated with ICI plus chemotherapy, within-clone TAP-CPS discordance was associated with poorer survival outcomes for the SP263 assay. Similarly, pairwise analyses across clones revealed that discordant PD-L1 positivity was associated with poorer survival outcomes across all comparisons, whereas concordant positivity across all three clones was associated with the most favorable survival outcomes.
Despite high interobserver agreement for SP263 using TAP scoring, substantial discordance between TAP and CPS, and across clones was non-negligible. These discordances were associated with poorer clinical outcomes, underscoring the need for careful interpretation of PD-L1 positivity in the context of the scoring system and antibody clone used.

PMID:
42944820
Bibliographic data and abstract were imported from PubMed on 28 Oct 2026.

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