[Correlation between the Expression of PD-L1 in Pleural Effusion of Lung Adenocarcinoma and the Clinicopathological Features and Molecular Changes].

BACKGROUND: Pembrolizumab, an immunotherapy for advanced non-small cell lung cancer (NSCLC), needs to predict treatment response based on test results including immunohistochemistry (IHC), which detects the expression of programmed death ligand 1 (PD-L1). The aim of this study was to evaluate the feasibility of immunocytochemistry (ICC) in NSCLC cytology to detect PD-L1 and to investigate the correlation between PD-L1 expression and clinical pathology and molecular features.

METHODS: Sixty cases of lung adenocarcinoma pleural cytology were collected and PD-L1 sp263 reagent was used for immunocytochemical staining according to the manufacturer's instructions. Next-generation sequencing (NGS) was performed on pleural cytology specimens to explore its correlation.

RESULTS: Of the 60 cases of lung adenocarcinoma pleural effusion cell block, 35 cases were positive for PD-L1 expression, and the positive expression rate was 58.3%. The positive rate of PD-L1 expression in the specimens of our hospital was 33.3%, and there was no significant difference between the cytological specimens and the histological specimens (P>0.05). Of the 60 cytological specimens, 26 were tested for NGS, and 15 (57.7%) were found to have epidermal growth factor receptor (EGFR) mutations. No correlation was found between PD-L1 expression and EGFR mutation. The positive expression rate of PD-L1 were not correlated with the age and gender in the study population (P>0.05).

CONCLUSIONS: When no surgical specimens are available, pleural cytology cell block specimens can be used for immunocytochemical detection of PD-L1, and the results are feasible.