Turning Fluids into Data for Precision Oncology: A Multidisciplinary Tumor Board Approach to Malignant Pleural Effusions

<b>Background</b>: Malignant pleural effusion (MPE) represents a frequent and clinically challenging manifestation of advanced malignancy, particularly in metastatic non-small cell lung cancer (NSCLC). Its management requires integration of diagnostic imaging, symptom-directed therapeutic strategies, and, increasingly, molecular profiling technologies. Recent advancements in this field based on liquid medium (so-called liquid biopsy) have achieved a significant increase in sensitivity, enhancing our ability to investigate biofluids and suggesting their potential integration into standard diagnostic practices, far beyond the canonical plasma biopsies. Fluid obtained from MPE after cytological sample centrifugation is rich in cell-free DNA and less susceptible to nucleic acid degradation during processing, improving overall diagnostic accuracy. <b>Methods</b>: This narrative review summarizes current evidence on the clinical management of malignant pleural effusions in patients with metastatic NSCLC, integrating imaging, procedural management, and molecular profiling from a multidisciplinary tumor board perspective. The primary objective was to synthesize contemporary knowledge with particular attention to the feasibility, reliability, and reproducibility of pleural fluid-based molecular testing. <b>Results</b>: MPE poses diagnostic and therapeutic challenges for all members of the multidisciplinary tumor board, traditionally associated with an adverse prognosis. However, recent advances in cytopathology, histopathology, and liquid-based techniques demonstrate that MPE could be an important source of prognostic or predictive information. At the same time, optimal patient management requires careful integration of imaging findings and procedural strategies (such as pleurodesis or indwelling pleural catheters) with individualized systemic therapy selection. Cell-free DNA in pleural effusions is a promising field of exploration and study, potentially suitable for future guideline implementation, after validation in adequately powered studies, contributing to improving patient management, particularly useful in fragile subsets. <b>Conclusions:</b> The management of MPE in advanced NSCLC is evolving toward a multidisciplinary, precision-oriented model that integrates clinical evaluation, imaging, procedural interventions, and molecular testing. Liquid biopsy technology has gained enough analytical robustness and clinical feasibility to be a useful tool in routine analysis. Biofluid-based molecular testing may have outstanding potential, contributing to improving patient management, avoiding repetitive procedures, and optimizing the overall efficiency and cost-effectiveness of diagnostic practices. Moreover, collaborative projects among different specialties help in consolidating trust in the tumor board decision-making process.