Clinical characteristics and prognostic analysis of epidermal growth factor receptor–mutated non–small cell lung cancer patients with malignant pleural effusion.

e20755 Background: Malignant pleural effusion (MPE) is common in advanced non-small cell lung cancer (NSCLC) and typically indicates poor prognosis. Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are the standard first-line treatment for EGFR-mutated NSCLC, significantly improving survival and quality of life. This study explores the heterogeneous impact of MPE on survival outcomes in NSCLC patients receiving EGFR-TKIs across different clinical scenarios. Methods: This single-center retrospective study enrolled histologically or cytologically confirmed NSCLC patients. The MPE group underwent Indwelling Pleural Catheter (IPC) drainage with cytological confirmation. All patients had confirmed EGFR mutations and received first-line EGFR-TKI therapy. Primary endpoints were progression-free survival (PFS) and overall survival (OS). Secondary endpoints included Objective Response Rate (ORR) and Disease Control Rate (DCR). Results: From March 2017 to September 2024, 162 patients were enrolled: 48 with MPE at diagnosis and 114 without. After 1:2 Propensity Score Matching (PSM), 91 patients were analyzed, including 35 with MPE. Compared to those without MPE, patients with MPE had significantly shorter median PFS (10.0 vs. 14.2 months; HR 1.872, 95% CI 1.196–2.928; p = 0.005) and median OS (28.3 vs. 33.8 months; HR 1.877, 95% CI 1.130–3.118; p = 0.013). Among 71 patients receiving first-line third-generation EGFR-TKIs after PSM (28 with MPE), those with MPE also showed significantly shorter mPFS (10.6 vs. 16.6 months; HR 2.116, 95% CI 1.265–3.539; p = 0.003) and mOS (28.3 vs. 38.5 months; HR 2.183, 95% CI 1.155–4.128; p = 0.014). Subgroup analyses suggested that the prognostic effect of MPE varied across different clinical subgroups (e.g., brain, liver, bone metastases), indicating that its impact may be modulated by metastatic patterns and other clinical characteristics. Conclusions: In the context of standard first-line EGFR-TKI therapy, patients with MPE had significantly reduced survival benefits. Even with first-line third-generation EGFR-TKIs, their survival remained markedly inferior to those without MPE. In the current EGFR-TKI treatment landscape, risk stratification based solely on MPE presence may be inadequate. Incorporating clinical subgroup characteristics into a refined assessment could enable more accurate prognostic evaluation.