Expression and clinical significance of programmed death ligand-1 evaluated by 22C3 antibody in pleural effusion metastatic non-small-cell lung cancer.

Objective: Programmed death ligand-1 (PD-L1) is involved in tumor immune escape and is an important target molecule for the immunotherapy of non-small-cell lung cancer (NSCLC). The expression of PD-L1 affects NSCLC invasion, metastasis, and patient survival. This study aims to explore the levels of PD-L1, as identified by the 22C3 antibody, in the malignant pleural effusion of patients suffering from advanced NSCLC, and to determine its clinical implications. Material and Methods: A two-step immunohistochemical EnVision assay was used to evaluate the expression of PD-L1 by the 22C3 antibody in 149 malignant pleural fluid cell wax clots of NSCLC. The relationship between PDL1 expression and clinicopathological characteristics, anaplastic lymphoma kinase (ALK) expression, epidermal growth factor receptor (EGFR) mutation, and overall survival (OS) time of patients with NSCLC was analyzed. Results: Positive expression of PD-L1 in malignant pleural fluid of NSCLC was observed as follows: Positive (<1%: 11.4%), positive (1-49%: 19.5%), and positive (≥50%: 11.4%), with a total positive rate of 42.3%. There was a significant association between PD-L1-positive expression and factors such as tumor differentiation, lymph node metastasis, and metastasis to other organs ( Conclusion: Immunohistochemical detection of PD-L1 expression in malignant pleural fluid of advanced NSCLC provides a basis for clinical tumor immunotherapy. Immunohistochemical detection of PD-L1 expression in malignant pleural fluid of advanced NSCLC is minimally invasive, simple, and fast, particularly for metastatic NSCLC where malignant pleural fluid is the first symptom, offering significant clinical application value.