Utility of PD‐L1 immunocytochemistry using body‐fluid cell blocks in patients with non‐small‐cell lung cancer

Abstract

Background The expression of programmed cell death ligand‐1 (PD‐L1) is a biomarker in patients with non‐small‐cell lung carcinoma (NSCLC). Patients with advanced‐stage NSCLC receive a variety of molecular genetic tests, possibly resulting in insufficient tissue for immunoassay of PD‐L1. Thus, to determine whether effusion fluid specimens are a reliable alternative to tissue specimens for PD‐L1 testing, we compared the results of PD‐L1 immunostaining using body‐fluid cell blocks and tumor tissues. Methods PD‐L1 immunostaining was performed in 62 paired samples of cytology cell blocks (ie, immunocytochemistry) and tumor tissues (ie, immunohistochemistry) from 36 patients using the E1L3N, SP142, and SP263 anti PD‐L1 antibody clones. Of the 62 cytology specimens, 50 were from malignant effusion fluid. PD‐L1 expression was scored as the percentage of tumor cells with clear membranous staining. Results A strong positive correlation was observed between the immunostains on cytology cell blocks and tumor tissue (Pearson's correlation coefficient, R = .804, P < .001). When the score was categorized as <1%, ≥1% and <10%, ≥10% and <50%, and ≥50%, the overall concordance rate was 74.2% (46/62, Cohen's k = 0.568). After dichotomizing the cases using cutoff values of 1%, 10%, and 50%, the concordance rates were 84% to 100% for both adenocarcinoma and squamous cell carcinoma. The concordance rate was higher in patients with NSCLC with an EGFR mutation and using the SP263 rather than the E1L3N clone. Conclusion The results of PD‐L1 immunostaining of cell blocks, particularly from effusion fluid, reflect the PD‐L1 expression status of NSCLC tissue.

PD-L1 Testing in Cytological Non-Small Cell Lung Cancer Specimens: A Comparison with Biopsies and Review of the Literature

“…In studies with cytology fixed in formalin, that is, excluding studies with nonformalin or mixed formalin/nonformalin fixation, the concordance with paired histological specimens was 81–82% (333–336/410 cases) at cutoff 1% and 88–89% (316–317/358 cases) at cutoff 50% based on 7 studies [38, 39, 48, 50, 58, 60, 62]. If instead, only including studies with cytology fixed in nonformalin fixatives, excluding mixed formalin/nonformalin fixation, the concordance with paired histological specimens was 79–81% (500–512/633 cases) at cutoff 1% and 88–89% (554–565/633 cases) at cutoff 50% based on 9 studies including the Lund cohort from the present study [41, 45, 46, 49, 52, 55, 56, 62].…”

“…Still, the overall concordance of PD-L1 expression between cytology and histology was rather good based on our results and previously published studies. In the literature, discordant cases typically show either higher score in cytology or in histology [39, 42, 43, 55, 66], which is expected due to heterogeneity of PD-L1 expression [24-28, 67]. However, the range of concordance was quite broad, 62–100% at cutoff 1% and 67–100% at cutoff 50% based on 25 publications.…”

Comparative evaluation of PD‐L1 expression in cytology imprints, circulating tumour cells and tumour tissue in non‐small cell lung cancer patients

“…Although the 28‐8 antibody clone was used in this study as it is the standard antibody used for routine clinical diagnostics of NSCLC at the department of Pathology in Hamburg, a high degree of agreement between the 28‐8 and 22C3 PD‐L1 antibody clones for histological and cytological samples staining results have been described before [10,16]. A consistently lower positivity rate has been described for the SP142 antibody [17,18].…”

Immunoexpression of oral brush biopsy enhances the accuracy of diagnosis for oral lichen planus and lichenoid lesions

“…The concordance for individual proteins in this study is consistent with the literature where concordance rates have ranged between 84% and 100%. 25 This highlights the significance of this method as a reliable, minimally-invasive tool for molecular analysis.…”