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Aims: A common concern among pathologists scoring PD‐L1 immunohistochemical staining is interobserver and intraobserver variability. We assessed the interobserver and intraobserver reproducibility of PD‐L1 scoring among trained pathologists using a combined positive score (CPS; tumour cell and tumour‐associated immune cell staining). Methods and results: Data were collected for 2 years (2017–2019) from 456 pathologists worldwide. Digital training encompassed unique, tumour‐specific training, and test sets. Samples were stained using PD‐L1 IHC 22C3 pharmDx and evaluated at specific CPS cutoffs for gastric cancer (GC), cervical cancer (CC), urothelial cancer (UC), oesophageal cancer (OC), and head and neck squamous cell carcinoma (HNSCC). Pathologists underwent expert‐to‐peer training and scored 20 blinded samples on day 1 and 25 blinded samples on day 2 (including 15 of the day 1 samples). Interobserver and intraobserver reproducibility were assessed. For GC (120 observers) and CC (32 observers) samples assessed at CPS ≥1, average interobserver agreement was 91.5% and 91.0%, respectively, and average intraobserver agreement was 90.2% and 96.6%, respectively. For UC (139 observers) and OC (52 observers) samples measured at CPS ≥10, average interobserver agreement was 93.4% and 93.7%, respectively, and average intraobserver agreement was 92.0% and 92.5%, respectively. For HNSCC samples (113 observers), average interobserver agreement was 94.1% at CPS ≥1 and 86.5% at CPS ≥20; intraobserver agreement was 94.7% at CPS ≥1 and 90.5% at CPS ≥20. Conclusion: The consistently high interobserver and intraobserver concordance rates support the effectiveness of face‐to‐face training of many global pathologists for scoring PD‐L1 CPS across multiple indications at several specific cutoffs. [ABSTRACT FROM AUTHOR]

Aims: The aim of this multicentre study was to harmonize programmed death‐ligand 1 (PD‐L1) immunohistochemistry (IHC) and melanoma scoring. To provide a reference for PD‐L1 expression independently of the IHC protocol, PD‐L1 mRNA expression was compared with IHC. Methods and results: Standardized PD‐L1 assays (22C3, 28–8, SP142, SP263) and laboratory‐developed tests (QR1, 22C3) were evaluated on three IHC platforms with a training set (seven cases). mRNA expression was determined by RNAscope (CD274/PD‐L1 probe) and analysed with image analysis. PD‐L1 IHC findings were scored by seven blinded pathologists using the tumour proportion score (TPS), the combined positive score (CPS), and the MELscore. This method was validated by three blinded pathologists on 40 metastatic melanomas. Concordances among various antibody/platforms were high across antibodies [intraclass correlation coefficient (ICC) >0.80 for the CPS], except for SP142. Two levels of immunostaining intensity were observed: high (QR1 and SP263) and low (28–8, 22C3, and SP142). Reproducibilities across pathologists were higher for QR1 and SP263 (ICC ≥0.87 and ICC ≥0.85 for the TPS and the CPS, respectively). QR1, SP263 and 28–8 showed the highest concordance with mRNA expression. We developed a standardized method for PD‐L1 immunodetection and scoring, tested on 40 metastatic melanomas. Concordances among antibodies were excellent for all criteria, and concordances among pathologists were better for the MELscore than for other scores. Conclusion: Harmonization of PD‐L1 staining and scoring in melanomas with good concordance is achievable with the PD‐L1 IHC protocols applied to other cancers; this reproducible approach can simplify daily practice. [ABSTRACT FROM AUTHOR]

Aims: The introduction of immunotherapy for patients with head and neck squamous cell carcinoma (HNSCC) raises the need for harmonisation between different types of antibody and immunohistochemistry platform for evaluating the expression of PD-L1 by use of the combined positive score (CPS) in this tumour. The aim of this study was to compare the expression of PD-L1 as determined with the CPS and two widely used assays (the 22C3 PharmDx assay and the SP263 assay) in a cohort of HNSCCs. Methods and results: We analysed 43 whole sections of HNSCC with two different anti-PD-L1 antibodies, 22C3 and SP263. The results, expressed as the CPS, were evaluated by 10 trained pathologists and statistical analyses were performed. We found a very similar results for PD-L1 expression between the 22C3 PharmDx assay and the SP263 assay in our cohort, and a strong and significant correlation between the two assays for all specimens (P < 0.0001). The interobserver reliability among pathologists for the continuous scores of CPS with the intraclass correlation coefficient and the correlation between the two assays were both good. Moreover, the rate of agreement between assays was high at all cut-offs and was best for the most relevant cut-off of CPS = 1, and the kappa values were always in the range of almost perfect. Conclusions: Two different assays (the 22C3 PharmDx assay and SP263 assay) for PD-L1 in HNSCC showed high agreement. These data suggest that these two assays are interchangeable in the selection of patients with HNSCC for immunotherapy. [ABSTRACT FROM AUTHOR]

Aims: The introduction of immunotherapy for patients with head and neck squamous cell carcinoma (HNSCC) raises the need for harmonisation between different types of antibody and immunohistochemistry platform for evaluating the expression of PD‐L1 by use of the combined positive score (CPS) in this tumour. The aim of this study was to compare the expression of PD‐L1 as determined with the CPS and two widely used assays (the 22C3 PharmDx assay and the SP263 assay) in a cohort of HNSCCs. Methods and results: We analysed 43 whole sections of HNSCC with two different anti‐PD‐L1 antibodies, 22C3 and SP263. The results, expressed as the CPS, were evaluated by 10 trained pathologists and statistical analyses were performed. We found a very similar results for PD‐L1 expression between the 22C3 PharmDx assay and the SP263 assay in our cohort, and a strong and significant correlation between the two assays for all specimens (P < 0.0001). The interobserver reliability among pathologists for the continuous scores of CPS with the intraclass correlation coefficient and the correlation between the two assays were both good. Moreover, the rate of agreement between assays was high at all cut‐offs and was best for the most relevant cut‐off of CPS ≥ 1, and the kappa values were always in the range of almost perfect. Conclusions: Two different assays (the 22C3 PharmDx assay and SP263 assay) for PD‐L1 in HNSCC showed high agreement. These data suggest that these two assays are interchangeable in the selection of patients with HNSCC for immunotherapy. [ABSTRACT FROM AUTHOR]