Comparative cell-free mutation analysis for the diagnosis of malignant pleural effusion in lung cancer patients: The Liquid Pleura Project

Introduction Malignant pleural effusion (MPE) in lung cancer patients (LCP) reduces treatment efficacy and quality of life. However, conventional pathological assessment does identify MPE in less than 50% of LCP with unclear PE. The aim of this prospective observational study was to assess whether cell-free mutation analysis of unclear PE in LCP helped identify MPE based on identical mutation patterns.

Methods LCP with unclear PE underwent thoracocentesis. PE and blood were transferred to cell-free DNA stabilizing blood collection tubes. Genomic DNA was extracted from cell-free supernatant and targeted next generation sequencing mutation analysis was performed using a customized DNA panel that covers coding regions of 40 genes. Patients with PE due to decompensated heart failure served as a tumor-free negative control (NC).

Results All LCP (N=30, 43% women) had advanced tumor stage (10% stage III, 90% stage IV, 77% adenocarcinoma squamous cell carcinoma 13%). The most prevalent mutations in the tumor tissue, PE, and blood were TP53 (67%, 70%, 43%, respectively), KRAS (33%, 23%, 27%, respectively), EGFR (17%, 7%, 10%, respectively), and PIK3CA (10%, 17%, 0%, respectively). We found no genetic alterations within the PE of the 5 non-malignant NC. In 12/30 (40%) cases, we identified MPE by means of conventional pathological assessment. Of those 12, 3 LCP were without mutations. In the remaining 9/9 (100%) cases, we identified at least one identical mutation in the PE compared to the tumor tissue. In 18/30 (60%) cases, we did not identify MPE by means of conventional assessment. Of those 18, 4 LCP were without mutations. In the remaining 12/14 (86%) cases, we identified at least one identical mutation in the PE compared to the tumor tissue suggesting MPE after all, with the following characteristics: sensitivity 42%, specificity 100%, positive predictive value 100%, negative predictive value 14%. In several LCP, the variant allele frequencies of TP53, KRAS, EGFR, and PIK3CA were even higher in the PE than in the tumor tissue.

Conclusion Comparative cell-free mutation analysis of PE helped identify MPE, even though conventional pathological assessment was negative for malignancy (86% in non-MPE). Cell-free mutation analysis of PE could improve therapeutic decision making in daily routine practice.

Publication History

Article published online:
18 March 2025