A comparative study of PD-L1 immunohistochemical assays with four reliable antibodies in thymic carcinoma

Abstract

Currently, four immunohistochemical assays are registered with the US Food and Drug Administration to detect the expression of PD-L1. We investigated the PD-L1 expression in thymic carcinomas using these four diagnostic assays. The cases of 53 patients were reviewed and their specimens were subjected to four PD-L1 assays with different antibodies (SP142, SP263, 22C3, and 28-8). The PD-L1 expression in tumor cells (TCs) and immune cells (ICs) was evaluated. In TCs, the four assays showed similar scores in each case. Histopathologically, high TC scores were observed in squamous cell carcinomas (SqCCs). Meanwhile, there were no significant relationships among the IC scores in the four assays. In SqCCs, the high expression of PD-L1 (defined as ≥50% TC score) in TCs tended to be associated with early stage cancer. The patients with high expression levels of PD-L1 tended to show longer overall survival in the 22C3 assays (p=0.0200). In thymic carcinomas, the staining pattern showed high concordance among the four assays when TCs – rather than ICs – were stained. High PD-L1 positivity in TCs, especially in SqCCs, indicated that PD-1/PD-L1 targeted therapy may be a promising therapeutic approach.

The prognostic impact of programmed cell death 1 and its ligand and the correlation with epithelial‐mesenchymal transition in thymic carcinoma

“…However, there are several problems such as sensitivity and appropriate cutoff in the IHC assays. From our results, EMT markers may be useful surrogate markers for case selection of ICI after anticancer agent …”

“…From our results, EMT markers may be useful surrogate markers for case selection of ICI after anticancer agent. 19 Our study has some limitations. The first limitation is the small sample size.…”

“…Several antibodies for PD‐L1 assays are commercially available. Sakane et al and other groups showed differences and concordance between antibodies in terms of IHC intensity and the cutoff point in TC . A third difference is whether the sample used for IHC staining was obtained before or after IT.…”

“…Sakane et al and other groups showed differences and concordance between antibodies in terms of IHC intensity and the cutoff point in TC. [19][20][21] A third difference is whether the sample used for IHC staining was obtained before or after IT. The former groups disregard the effect of IT in their PD-L1 IHC results.…”

A mutation analysis of the EGFR pathway genes, RAS, EGFR, PIK3CA, AKT1 and BRAF, and TP53 gene in thymic carcinoma and thymoma type A/B3

“…3 At present there is no therapy more effective than complete surgical resection for both tumours, although some novel therapies, including immunotherapy, have been developed for these tumours. [6][7][8][9] The epidermal growth factor receptor (EGFR) signalling pathway plays an important role in the regulation of tumour cell survival and proliferation of tumour cells in various types of oncological cases. [10][11][12][13] Many anti-EGFR agents have been developed and have exhibited significant antitumour activity in patients with lung cancer, colorectal cancer and head and neck cancer.…”