B-087 Comparative study of the detection of Driver gene mutations in pleural effusion and peripheral blood ctDNA in patients with non-small cell lung cancer

Abstract

Pleural effusion (PE) is frequently observed in advanced lung cancer and has been shown to contain both cell-free tumor DNA and tumor cells. Molecular profiling of PE offers a minimally invasive approach for detecting tumor driver mutations to guide clinical decision-making, particularly when tumor tissue is unavailable. This study aims to evaluate and compare the efficacy and accuracy of gene alteration detection between pleural effusion and peripheral blood circulating tumor DNA (ctDNA) in patients with advanced non-small cell lung cancer (NSCLC). Between November 2024 and December 2025, 23 patients with stage IV NSCLC were enrolled. Peripheral blood and pleural effusion samples were collected from all participants. The cohort consisted of 8 males and 15 females, aged 48–84 years (median 64 years). Twenty-two patients had metastatic adenocarcinoma, and one had metastatic adenocarcinoma with squamous differentiation. DNA was extracted from both sample types using the Qiagen DNA Extraction Kit according to the manufacturer’s protocol. Driver gene mutations in ctDNA were detected using NGS technology. All 23 NSCLC patients were analyzed for genetic alterations, including single nucleotide variants (SNVs), insertions/deletions (indels), fusions, and copy number variations (CNVs).1. Detection of driver gene mutations in pleural effusion Gene mutations were identified in 20 out of 23 pleural effusion specimens, yielding a detection rate of 86.9% (20/23). Among mutation-positive cases, nine (45%, 9/20) harbored the L858R point mutation, two of which also carried a concurrent L790M mutation. The remaining 11 mutation-positive specimens exhibited a variety of alterations, including E746_A750del, L858_K860delinsRAI, L747_T751delinsP, ML4-ALK fusion, T790_L792delinsMQF, L792F, L858R (c.2573_2574delinsGA), NTRK1 rearrangement, and MET amplification (dup(7)(q31.2)).2. Detection of driver gene mutations in peripheral blood Mutations were detected in 15 of 23 peripheral blood specimens, corresponding to a detection rate of 65.2% (15/23). Of these, 10 (66.7%, 10/15) presented the L858R point mutation. The other mutation profiles included E746_A750del, T790M, and MET amplification (dup(7)(q31.2)).3. Concordance and mutation abundance between pleural effusion and peripheral blood in paired samples Using peripheral blood as the reference, pleural effusion ctDNA demonstrated 100% sensitivity. Notably, mutations such as T790M, L858R, and L792F were detected in pleural effusion but not in matched peripheral blood samples in seven patients. Moreover, mutation allele frequencies were generally higher in pleural effusion than in peripheral blood ctDNA. The overall concordance rate between the two sample types was 73.9%. As an important component of liquid biopsy, pleural effusion ctDNA represents a promising tumor biomarker that can dynamically reflect genetic alterations during cancer progression. Compared with tissue biopsy, it offers several advantages, including minimal invasiveness, ease of collection, better patient acceptance, and feasibility for serial sampling. In this study, mutational profiles derived from pleural effusion and peripheral blood ctDNA were largely consistent in advanced NSCLC patients, with pleural effusion providing higher detection rates and greater mutation abundance. These findings support the clinical utility of pleural effusion ctDNA analysis for genomic profiling in NSCLC.