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Abstract
Aims At the time of analysis, two widely used, drug-specific, tumour-cell programmed death ligand 1 (PD-L1) assays were approved by the US Food and Drug Administration for anti-PD-1 therapies: the Dako PD-L1 immunohistochemistry (IHC) 28-8 pharmDx assay and the Dako PD-L1 IHC 22C3 pharmDx assay. Given that the majority of current PD-L1 testing in US clinical practice is performed at commercial reference laboratories, we aimed to evaluate the concordance of the 28-8 and 22C3 assays in a real-world setting.
Methods Matched PD-L1 IHC 28-8 and 22C3 results from routine assessment were obtained from 1930 patients, including 412 confirmed to have lung cancer, submitted from hospitals in over 38 US states/territories. Biopsies were stained, reviewed and scored by trained/certified pathologists at a single cancer reference laboratory between 2015 and 2017. Rate of concordance between assay findings was assessed by Bland-Altman analysis; overall per cent agreement (OPA), positive per cent agreement and negative per cent agreement; and Cohen’s kappa.
Results PD-L1 IHC 28-8 and 22C3 displayed strong correlation across all samples and in samples with a confirmed lung cancer diagnosis irrespective of biopsy site. The OPA was 97%–98% for all samples, depending on the expression level defining PD-L1 positivity. In the Bland-Altman analysis, the mean difference in percentage of tumour cells positively stained for PD-L1 between the paired assay findings was –0.80% for all samples and –0.93% in samples with a confirmed lung cancer diagnosis.
Conclusions These data, in conjunction with recent findings, support the analytical concordance of the PD-L1 IHC 28-8 and 22C3 assays for assessing per cent tumour-cell membrane PD-L1 expression.
- lung cancer
- cancer
- immunohistochemistry
- diagnostics
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Footnotes
Handling editor Runjan Chetty.
Correction notice This article has been made Open Access since it was published Online First.
Contributors CB, MA, SS, VC and VB designed the study. MA, SS and VC performed all experiments. KZ and CJ performed the biostatistical analysis. All authors reviewed and approved the manuscript.
Funding This study was supported by Bristol-Myers Squibb.
Competing interests CB was employed by Bristol-Myers Squibb during the conduct of the study, and is currently an employee of Verily Life Sciences. KZ, CJ and VB are employed by Bristol-Myers Squibb. MA, VC and SS are employed by NeoGenomics Laboratories.
Patient consent Not required.
Ethics approval No ethics approval was required for this study because this study consisted of real-world patient samples assessed for PD-L1 expression by NeoGenomics Laboratories as a commercial provider of PD-L1 expression testing.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Bristol-Myers Squibb’s policy on data sharing can be found at https://www.bms.com/researchers-and-partners/independent-research/data-sharing-request-process.html.
Author note At the time of the study, Dr C Batenchuk was an employee of Bristol-Myers Squibb. Dr C Batenchuk is currently an employee of Verily Life Sciences.