A multicentre analytical comparison study of inter‐reader and inter‐assay agreement of four programmed death‐ligand 1 immunohistochemistry assays for scoring in triple‐negative breast cancer

Abstract

Aims Studies in various cancer types have demonstrated discordance between results from different programmed death‐ligand 1 (PD‐L1) assays. Here, we compare the reproducibility and analytical concordance of four clinically developed assays for assessing PD‐L1‐positivity in tumour‐infiltrating immune cells in the tumour area (PD‐L1‐IC‐positivity) in triple‐negative breast cancer (TNBC). Methods and results Primary TNBC resection specimens (n = 30) were selected based on their PD‐L1‐IC‐positivity per VENTANA SP142 (<1%: 15 cases; 1–5%: seven cases; >5%: eight cases). Serial histological sections were stained for PD‐L1 using VENTANA SP142, VENTANA SP263, DAKO 22C3 and DAKO 28‐8. PD‐L1‐IC‐positivity and tumour cell expression (≥1 versus <1%) were scored by trained readers from seven sites using online virtual microscopy. The adjusted mean of PD‐L1‐IC‐positivity for SP263 (7.8%) was significantly higher than those for the other three assays (3.7–4.9%). Differences in adjusted means were statistically significant between SP263 and the other three assays (P < 0.0001) but not between the three remaining assays when excluding SP263 (P = 0.0961–0.6522). Intra‐class correlation coefficients revealed moderate‐to‐strong inter‐reader agreement for each assay (0.460–0.805) and poor‐to‐strong inter‐assay agreement for each reader (0.298–0.678) on PD‐L1‐IC‐positivity. Conclusions In this first multicentre study of different PD‐L1 assays in TNBC, we show that PD‐L1‐IC‐positivity for SP142, 22C3 and 28‐8 was reproducible and analytically concordant, indicating that these three assays may be analytically interchangeable. The relevance of the higher PD‐L1‐IC‐positivity for SP263 should be further investigated.

SP142 PD-L1 Scoring Shows High Interobserver and Intraobserver Agreement in Triple-negative Breast Carcinoma But Overall Low Percentage Agreement With Other PD-L1 Clones SP263 and 22C3

“… 4 The only published study investigating SP142 PD-L1 interobserver agreement in TNBCs enriched around the 1% cutpoint reported an interclass correlation coefficient of 0.805 among 7 specifically trained pathologists in a limited cohort of cases (n=30). 5 …”

Immunohistochemical comparison of three programmed death-ligand 1 (PD-L1) assays in triple-negative breast cancer

“…Table 8 summarizes the comparisons of PD-L1 expression on ICs using different antibodies according to the results of previous studies and the present one. The rates of PD-L1 expression were relatively different among these studies [21][22][23][24][25]. The PD-L1 positivity rates using the SP142 assay ranged from 19.3% to 67.7% and those using the 22C3 assay ranged from 32.6% to 81% (the 22C3 assay was analyzed by a combined positive score).…”

“…The IMpassion130 trial clearly demonstrated that atezolizumab plus nab-paclitaxel significantly prolonged progression-free survival in advanced or metastatic PD-L1-positive TNBC patients [11]; the study defined PD-L1-positivity as PD-L1-expressing ICs �1% in the tumor area [11], which is the same definition used in this study. However, various immunohistochemical platforms have been developed to evaluate PD-L1 expression; thus, few studies have compared the differences between all the PD-L1 immunohistochemical assays in TNBC tissues [21][22][23][24][25]. For example, the 73-10 assay, which is the companion diagnostic tests for avelumab [16,36], has not yet been analyzed in TNBC tissues.…”

“…In lung cancer, some studies, including the Blueprint PD-L1 immunohistochemical assay comparison study, evaluated the differences in the properties of PD-L1 primary antibodies [18][19][20]. Although a few studies have analyzed PD-L1 immunoreactivity using the 22-8, 22C3, SP142, SP263, and E1L3N assays in TNBC patients [21][22][23][24][25], the immunoreactivity of PD-L1 using the 73-10 assay has not been compared with that of the SP142 assay. Thus, we aimed to evaluate PD-L1 immunoreactivity using the SP142, 73-10, and E1L3N assays in TNBC tissues.…”

Discordance of PD-L1 Expression at the Protein and RNA Levels in Early Breast Cancer

“…In the present study, we evaluated the level of concordance and spatial heterogeneity of PD-L1 expression using a multi-level methods approach, demonstrating substantial discordance among the different methodologies. In comparison, previous comparative studies have been limited in that they mostly evaluated the PD-L1 IHC expression using different antibody clones with the sole focus on TNBC [ 22 , 23 ]. In line with previous results [ 6 ], we show here that PD-L1 positivity was highly concordant between SP142 and SP263 immunohistochemical antibodies, while the observed level of discordance varied depending on the applied method.…”