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Updated: Mar 6, 2026
Using 22C3 Anti-PD-L1 Antibody Concentrate on Biopsy and Cytology Samples from Non-small Cell Lung Cancer Patients
Published on: September 25, 2018
A Prospective, Multi-institutional, Pathologist-Based Assessment of 4 Immunohistochemistry Assays for PD-L1
David L Rimm1, Gang Han2, Janis M Taube3
1Department of Pathology, Yale University School of Medicine, New Haven, Connecticut.
Importance:
Four assays registered with the US Food and Drug Administration (FDA) detect programmed cell death ligand 1 (PD-L1) to enrich for patient response to anti-programmed cell death 1 and anti-PD-L1 therapies. The tests use 4 separate PD-L1 antibodies on 2 separate staining platforms and have their own scoring systems, which raises questions about their similarity and the potential interchangeability of the tests.
Objective:
To compare the performance of 4 PD-L1 platforms, including 2 FDA-cleared assays, 1 test for investigational use only, and 1 laboratory-developed test.
Design, Setting, And Participants:
Four serial histologic sections from 90 archival non-small cell lung cancers from January 1, 2008, to December 31, 2010, were distributed to 3 sites that performed the following immunohistochemical assays: 28-8 antibody on the Dako Link 48 platform, 22c3 antibody on the Dako Link 48 platform, SP142 antibody on the Ventana Benchmark platform, and E1L3N antibody on the Leica Bond platform. The slides were scanned and scored by 13 pathologists who estimated the percentage of malignant and immune cells expressing PD-L1. Statistical analyses were performed from December 1, 2015, to August 30, 2016, to compare antibodies and pathologists' scoring of tumor and immune cells.
Main Outcomes And Measures:
Percentages of malignant and immune cells expressing PD-L1.
Results:
Among the 90 samples, the SP142 assay was an outlier, with a significantly lower mean score of PD-L1 expression in both tumor and immune cells (tumor cells: 22c3, 2.96; 28-8, 3.26; SP142, 1.99; E1L3N, 3.20; overall mean, 2.85; and immune cells: 22c3, 2.15; 28-8, 2.28; SP142, 1.62; E1L3N, 2.28; overall mean, 2.08). Pairwise comparisons showed that the scores from the 28-8 and E1L3N tests were not significantly different but that the 22c3 test showed a slight (mean difference, 0.24-0.30) but statistically significant reduction in labeling of PD-L1 expression in tumor cells. Evaluation of intraclass correlation coefficients (ICCs) between antibodies to quantify interassay variability for PD-L1 expression in tumor cells showed high concordance between antibodies for tumor cell scoring (0.813; 95% CI, 0.815-0.839) and lower levels of concordance for immune cell scoring (0.277; 95% CI, 0.222-0.334). When examining variability between pathologists for any single assay, the concordance between pathologists' scoring for PD-L1 expression in tumor cells ranged from ICCs of 0.832 (95% CI, 0.820-0.844) to 0.882 (95% CI, 0.873-0.891) for each assay, while the ICCs from immune cells for each assay ranged from 0.172 (95% CI, 0.156-0.189) to 0.229 (95% CI, 0.211-0.248).
Conclusions And Relevance:
The assay using the SP142 antibody is an outlier that detected significantly less PD-L1 expression in tumor cells and immune cells. The assay for antibody 22c3 showed slight yet statistically significantly lower staining than either 28-8 or E1L3N, but this significance was detected only when using the mean of 13 pathologists' scores. The pathologists showed excellent concordance when scoring tumor cells stained with any antibody but poor concordance for scoring immune cells stained with any antibody. Thus, for tumor cell assessment of PD-L1, 3 of the 4 tests are concordant and reproducible as read by pathologists.
Insights
Three of four programmed cell death ligand 1 (PD-L1) assays show concordance for tumor cell assessment. The SP142 assay was an outlier, detecting significantly less PD-L1 expression. Pathologist scoring showed high concordance for tumor cells but poor concordance for immune cells.
Area of Science:
- Oncology
- Immunotherapy
- Biomarker Assay Development
Background:
- Four US Food and Drug Administration (FDA)-registered assays detect programmed cell death ligand 1 (PD-L1) to guide patient selection for anti-PD-1/PD-L1 therapies.
- These assays utilize distinct PD-L1 antibodies and staining platforms, raising questions about their comparability and interchangeability.
Purpose of the Study:
- To compare the performance of four PD-L1 detection platforms, including FDA-cleared, investigational, and laboratory-developed tests.
- To evaluate inter-assay variability and pathologist concordance in scoring PD-L1 expression.
Main Methods:
- Archival non-small cell lung cancer (NSCLC) tissue sections were stained using four different PD-L1 immunohistochemical assays (28-8, 22c3, SP142, E1L3N).
- Thirteen pathologists scored PD-L1 expression on tumor and immune cells.
- Statistical analyses, including intraclass correlation coefficients (ICCs), were performed to assess inter-assay and inter-pathologist variability.
Main Results:
- The SP142 assay demonstrated significantly lower PD-L1 expression in both tumor and immune cells compared to the other three assays.
- High concordance (ICC=0.813) was observed between antibodies for tumor cell PD-L1 scoring, but lower concordance (ICC=0.277) for immune cell scoring.
- Pathologists showed excellent concordance (ICCs ranging from 0.832-0.882) when scoring tumor cells but poor concordance (ICCs ranging from 0.172-0.229) for immune cells.
Conclusions:
- Three of the four PD-L1 assays (28-8, 22c3, E1L3N) demonstrate concordance and reproducibility for tumor cell assessment in NSCLC.
- The SP142 assay is an outlier and should be considered distinct.
- Reliable assessment of PD-L1 expression in immune cells remains a challenge due to significant inter-pathologist variability across all assays.
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