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Mod Pathol. 2019 Jun 23. doi: 10.1038/s41379-019-0307-8. [Epub ahead of print]

A comparability study of immunohistochemical assays for PD-L1 expression in hepatocellular carcinoma.

Author information

1
Department of Pathology, the Second Xiangya Hospital of Central South University, Changsha, Hunan, China.
2
Department of Pathology, the Fourth Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, China.
3
Department of Pathology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing, Jiangsu, China.
4
Department of Pathology, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong, China.
5
Department of Pathology, the Sixth Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong, China.
6
Department of Anatomical and Cellular Pathology, State Key Laboratory of Translational Oncology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
7
Department of Clinical Oncology, State Key Laboratory of Translational Oncology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
8
Institute of Digestive Disease, Partner State Key Laboratory of Digestive Disease, The Chinese University of Hong Kong, Hong Kong, China.
9
Division of Hepatobiliary and Pancreatic Surgery, Department of Surgery, The Chinese University of Hong Kong, Hong Kong, China.
10
Department of Anatomical and Cellular Pathology, State Key Laboratory of Translational Oncology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China. awh_chan@cuhk.edu.hk.

Abstract

Programmed death ligand 1 (PD-L1) protein expression by immunohistochemistry is a promising biomarker for PD-1/PD-L1 blockade in hepatocellular carcinoma. There are a number of commercially available PD-L1 assays. Our study aimed to compare the analytical performance of different PD-L1 assays and evaluate the reliability of pathologists in PD-L1 scoring. Consecutive sections from tumor samples from 55 patients with surgically resected primary hepatocellular carcinoma were stained with four standardized PD-L1 assays (22C3, 28-8, SP142, and SP263). We also correlated the PD-L1 protein level by immunohistochemistry with the mRNA level of those genes associated with tumor immune microenvironment by the NanoString platform. Five pathologists independently assessed PD-L1 expression on tumor cells [tumor proportion score] together with tumor-infiltrating immune cells (combined positive score). The 22C3, 28-8, and SP263 assays had comparable sensitivity in detecting PD-L1 expression, whereas the SP142 assay was the least sensitive assay. The inter-assay agreement measured by intraclass correlation coefficients for the tumor proportion score and combined positive score were 0.646 and 0.780, respectively. The inter-rater agreement was good to excellent (the overall intraclass correlation coefficient for the tumor proportion score and combined positive score was 0.946 and 0.809, respectively). Pathologists were less reliable in scoring combined positive score than tumor proportion score, particularly when using the SP142 assay. Up to 18% of samples were misclassified by individual pathologists in comparison to the consensus score at the cutoff of combined positive score ≥ 1. The combined positive score by the 22C3 assay demonstrated the strongest correlation with immune-related gene mRNA signatures, closely followed by combined positive scores by the 28-8 and SP263 assays. In conclusion, the 22C3, 28-8, and SP263 assays are highly concordant in PD-L1 scoring and suggest the interchangeability of these three assays. Further improvement of the accuracy in assessing PD-L1 expression at a low cutoff is still necessary.

PMID:
31231126
DOI:
10.1038/s41379-019-0307-8

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