Retrospective prognostic evaluation and single-cell transcriptomic analyses of non-small cell lung carcinoma with malignant pleural effusion.

Background: The impact of malignant pleural effusion (MPE) and intrapleural infusion therapy on the prognosis of non-small cell lung carcinoma (NSCLC) patients receiving immunochemotherapy remains unclear. Investigating the tumor microenvironment of MPE may offer valuable insights for improving outcomes, yet current research in this area is limited. The aim of this study is to explore the impact of MPE and intrapleural infusion therapy on prognosis in the era of immunochemotherapy, and to identify potential therapeutic targets for improving the prognosis of MPE patients.

Methods: This study included advanced NSCLC patients without driver mutations who underwent first-line immunochemotherapy at Shandong Cancer Hospital and Institute between December 2018 and June 2023. Progression-free survival (PFS) and overall survival (OS) were the primary endpoints. Propensity score matching (PSM) and survival analysis were performed. Single-cell data of primary tumors (PTs) and MPE were obtained from GSE131907. This study performed cell subpopulation comparison, copy number variation (CNV) analysis of epithelial cells, differential gene expression analysis of malignant cells, gene set variation analysis (GSVA), single-cell regulatory network inference and clustering (SCENIC) analysis, and cell-cell interaction analysis.

Results: A total of 116 patients with MPE and 279 patients without MPE were included in this study; after matching, each group included 112 patients. Patients with MPE had significantly shorter median PFS and OS compared to those without MPE (PFS: 8.0 vs. 16.0 months, P<0.001; OS: 20.0 months vs. not reached, P<0.001). Among MPE patients, intrapleural drug infusion did not significantly impact survival (PFS: 7.0 vs. 11.0 months, P=0.09; OS: 20.0 vs. 19.0 months, P=0.77). Genes such as GTSF1, MAGEA3, XIST, and FGB were significantly upregulated in malignant cells from MPE. In the MPE microenvironment, CD4⁺ T cells were the dominant T cell subset, naive B cells were selectively enriched, and monocytes/macrophages made up the majority of myeloid cells. The INTERFERON_ALPHA_RESPONSE pathway was enriched in diverse immune cell types from MPE, although this enrichment might not be statistically significant. Interferon regulatory factor 9 (IRF9) was widely upregulated in T cells, natural killer (NK) cells, B cells, and myeloid cells from MPE. Myeloid cells acted as the primary signal senders and receivers in the MPE microenvironment, while epithelial cells primarily functioned as signal senders.

Conclusions: Under immunochemotherapy, NSCLC patients with MPE still demonstrated poor prognosis. This provides an additional prognostic predictor for NSCLC patients receiving standard first-line treatment. However, intrapleural infusion of existing drugs did not improve survival in these patients. The high expression of certain genes in tumor cells from MPE may partly explain this unfavorable outcome. IRF9, which regulates type I interferon (IFN-I) signaling, was upregulated in MPE. Therefore, targeted delivery of IFN-I to the pleural cavity may offer a feasible approach for the treatment of MPE.