Programmed Death Ligand 1 Immunohistochemistry in Triple-Negative Breast Cancer: Evaluation of Inter-Pathologist Concordance and Inter-Assay Variability
- Authors
- Ahn, Soomin; Woo, Ji Won; Kim, Hyojin; Cho, Eun Yoon; Kim, Ahrong; Kim, Jee Yeon; Kim, Chungyeul; Lee, Hee Jin; Lee, Ji Shin; Bae, Young Kyung; Kwon, Youngmee; Kim, Wan Seop; Park, So Yeon
- Issue Date
- 6월-2021
- Publisher
- KOREAN BREAST CANCER SOC
- Keywords
- B7-H1 antigen; Immune checkpoint inhibitors; Immunohistochemistry; Observer variation; Triple negative breast cancer
- Citation
- JOURNAL OF BREAST CANCER, v.24, no.3, pp.266 - 279
- Indexed
- SCIE
SCOPUS
KCI
- Journal Title
- JOURNAL OF BREAST CANCER
- Volume
- 24
- Number
- 3
- Start Page
- 266
- End Page
- 279
- URI
- https://scholar.korea.ac.kr/handle/2021.sw.korea/137331
- DOI
- 10.4048/jbc.2021.24.e29
- ISSN
- 1738-6756
- Abstract
- Purpose: The programmed death ligand 1 (PD-L1) SP142 assay with a 1% immune cell (IC) cutoff is approved for the selection of advanced triple-negative breast cancer (TNBC) patients for atezolizumab treatment. We aimed to evaluate the interobserver concordance of PD-L1 scoring and inter-assay variability of various PD-L1 assays in TNBC. Methods: Thirty patients with primary TNBC were selected, and SP142, SP263, 22C3, and E1L3N assays were performed. PD-L1 staining in ICs and tumor cells (TCs) was scored by 10 pathologists who were blinded to the assay. The interobserver concordance among pathologists and the inter-assay variability of the four PD-L1 assays were analyzed. For SP142, the intraobserver concordance among the six pathologists was analyzed after training. Results: The adjusted means of PD-L1 IC scoring ranged from 6.2% to 12.9% for the four assays; the intraclass correlations showed moderate (0.584-0.649) reader concordance. The PD-L1 IC scoring with a 1% cutoff resulted in identical scoring in 40.0%-66.7% of cases and a poor to moderate agreement (Fleiss k statistic [FKS] = 0.345-0.534) for the four assays. The SP142 assay had the widest range of positive rate (56.5%400.0%), lowest number of cases with identical scoring, and lowest FKS at 1% cutoff. Pairwise comparison of adjusted means showed significantly decreased PD-Ll staining in SP142 compared with the other assays in both ICs and TCs. As for the intraobserver concordance in the SP142 assay, the overall percent agreement was 87.8% with a 1% IC cutoff. After training, the proportion of cases with identical scoring at a 1% IC cutoff increased to 70.0%; the FKS also increased to 0.610. Conclusion: The concordance of PD-L1 IC scoring among pathologists was low, at the 1% cutoff for the SP142 assay without training. SP142 showed the lowest PD-L1 expression in both IC and TC.
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