Systemic Inflammatory Biomarkers and Unsupervised Phenotyping of Surgical Pleurodesis Outcomes in Malignant Pleural Effusion: A Retrospective Single-Centre Study

Background: Pleurodesis is widely used to control malignant pleural effusion (MPE), but reliable pre-procedural predictors of success remain lacking. We assessed whether routinely available systemic inflammatory biomarkers predict short-term pleurodesis outcome and explored multidimensional inflammatory phenotypes. Methods: This retrospective single-center cohort included 144 patients who underwent pleurodesis for MPE between January 2021 and August 2025. Pre-procedural systemic immune-inflammation index (SII), neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and C-reactive protein (CRP) were evaluated using receiver operating characteristic analysis. K-means clustering, principal component analysis, and uniform manifold approximation and projection were used for exploratory phenotyping. Results: Complete success occurred in 100 patients (69.4%), failure in 35 (24.3%), and partial response in 9 (6.3%). None of the biomarkers discriminated success from failure (AUC: SII, 0.471; NLR, 0.409; PLR, 0.490; CRP, 0.544). Three exploratory clusters showed crude success rates of 88.9%, 72.3%, and 61.5%, respectively, but substantial overlap and lack of external validation precluded clinical interpretation. Conclusions: Single pre-procedural systemic inflammatory biomarkers should not be used alone to select patients for pleurodesis. Prospective multicenter studies integrating systemic markers with pleural biology and mechanical factors are warranted.