Real-world treatment patterns, procedures, and subgroup variation in lung cancer–associated malignant pleural effusion.

582 Background: Malignant pleural effusion (MPE) is a common and morbid complication of advanced cancer, particularly in non–small cell lung cancer (NSCLC), where it frequently signals stage IV disease. Since late 2016, the standard of care for metastatic NSCLC has evolved with first-line immunotherapy and, in oncogene-driven tumors, targeted therapies largely replacing chemotherapy alone. However, real-world adoption of these advances and their impact on patient subgroups with MPE remain poorly understood. Methods: We conducted a retrospective, cross-sectional analysis of adult patients with cancer-associated MPE treated between November 2016 and April 2025 at a large academic center. Patients were identified using ICD-10 codes. Demographic and clinical variables included age, gender, race, vital status, primary payor, tobacco history, and receipt of thoracentesis, pleurodesis, immunotherapy (ICI), platinum therapy, and targeted agents. We compared patients with MPE from lung cancer vs other cancers and examined disparities in treatment and outcomes by payor, smoking history, and treatment modality using descriptive statistics. Results: Among 7,411 patients with cancer and MPE, 2,836 (38.3%) had lung cancer. Lung cancer MPE patients were younger (median 67 vs 70), had higher mortality (71.3% vs 57.1%), and lower survival at cutoff (28.4% vs 42.6%). Thoracentesis was performed in 21.2% of lung MPE patients; pleurodesis use was low (2.6%), even among those receiving systemic therapy. Use of pleurodesis was lowest in Medicaid and highest in Medicare Advantage. Of 803 lung MPE patients receiving ICI, 591 (73.6%) also received platinum. Patients on ICI alone were older, less likely to undergo pleurodesis, and more likely to be deceased. Never-smokers (n=535) were predominantly female (69%) with high mortality (70%), suggesting possible enrichment for oncogene-driven disease. Pemetrexed and pembrolizumab were the most common agents. Medicaid and Medicaid-pending enrollees had the highest mortality (≥72%) and lowest rates of ICI+platinum receipt. Commercially insured patients had greater use of targeted therapy and pleurodesis. Among lung MPE patients, procedure rates and therapy intensity varied substantially by age, payor, and smoking status, with minimal utilization of palliative interventions. Compared to MPE from other tumors, lung MPE was associated with worse outcomes despite broader systemic therapy access. Conclusions: In this real-world cohort, patients with lung cancer–associated MPE experienced greater mortality, less pleurodesis, and wide variation in systemic therapy use by payor and clinical profile. These findings highlight underutilization of palliative interventions, disparities in ICI and platinum use, and the need for targeted quality improvement to ensure equitable MPE care.