ES07.02 Role of Pleural Fluid Molecular Markers and PD-L1 Testing

Abstract

Patients with pleural metastases or lymphatic metastases in 50-60% develop pleural effusions (PE). Conventional cytology is negative (CNPE) in up to 40% of malignant PEs. The cells in PE are in a different microenvironment, affecting biology and biomarkers' expression considering the impact of tumor-host cell interactions. Obtaining PE, an early diagnostic step provides important biomarkers; when other tissue samples might not be available. PE represents tumor heterogeneity; tumor cells in pleural effusions might represent more lesions than biopsies. There are studies involving genomic, transcriptomic, proteomic, and metabolomics. Circulating cell-free DNA from PF supernatants may provide relevant information to clinicians that might complement or replace invasive diagnostic procedures. Cytology negative and positive PE is useful in early decision-making and when no additional time is available for later diagnostics steps due to disease aggressiveness. Biomarkers show high specificity, and the low sensitivity limits the diagnostic value that might increase with the PE amount available. Molecular testing on PE specimens is becoming a feasible alternative to tissue biopsy for phenotyping malignant PEs in lung cancer patients. PE might be suitable for assessing PD-L1 expression in malignant cells, and we compare the results of those reported for histological specimens.