External quality assessment demonstrates that PD-L1 22C3 and SP263 assays are systematically different



Dodson, Andrew, Parry, Suzanne, Lissenberg-Witte, Birgit, Haragan, Alex ORCID: 0000-0002-9747-563X, Allen, David, O'Grady, Anthony, McClean, Emma, Hughes, Jamie, Miller, Keith and Thunnissen, Erik
(2020) External quality assessment demonstrates that PD-L1 22C3 and SP263 assays are systematically different. JOURNAL OF PATHOLOGY CLINICAL RESEARCH, 6 (2). pp. 138-145.

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Abstract

PD-L1 inhibitors are part of first line treatment options for patients with advanced non-small cell lung cancer. PD-L1 immunohistochemistry (IHC) assays act as either a companion or a complementary diagnostic. The purpose of this study is to describe the experience of external quality assurance (EQA) provider UK NEQAS ICC and ISH with the comparison of different PD-L1 assays used in daily practice. Three EQA rounds (pilot, run A and run B) were carried out using formalin fixed paraffin embedded samples with sample sets covering a range of epitope concentrations, including 'critical samples' near to clinical threshold cut-offs. An expert panel (n = 4) evaluated all returned slides simultaneously and independently on a multi-header microscope together with the participants own in-house control material. The tonsil sample was evaluated as 'acceptable' or 'unacceptable', and for the other samples the percentage of PD-L1 stained tumour cells were estimated in predetermined categories (<1%, 1 to <5%, 5 to <10%, 10 to <25%, 25 to <50%, 50 to <80%, 80 to 100%). In the pilot and the two subsequent runs the number of participating laboratories was 43, 69 and 76, respectively. The pass rate for the pilot run was 67%; this increased to 81% at run A and 82% at run B. For two 'critical samples', in runs A and B, 22C3 IHC had significantly higher PD-L1 expression than SP263 IHC (p < 0.001), whilst the PD-L1 scores for the other six samples were similar for all assays. In run A the laboratory developed tests (LDTs) using 22C3 scored lower than the commercial 22C3 tests (p = 0.01). After the initial testing, improvement in performance of PD-L1 IHC is shown for approved and LDT PD-L1 assays. Equivalency of approved PD-L1 22C3 and SP263 assays cannot be assumed as the scores cross the clinically relevant thresholds of 1% and 50% PD-L1 expression.

Item Type: Article
Uncontrolled Keywords: external quality assessment, PD-L1, predictive testing, immunohistochemistry, non-small cell lung cancer, companion diagnostic assays
Depositing User: Symplectic Admin
Date Deposited: 07 Jan 2020 09:35
Last Modified: 19 Jan 2023 00:11
DOI: 10.1002/cjp2.153
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3069422