The Prognostic Role of Tertiary Lymphoid Structures and Immune Microenvironment Signatures in Early-Stage EGFR-Mutant Lung Adenocarcinoma.

BACKGROUND/OBJECTIVES: The role of tertiary lymphoid structures (TLSs) in cancer prognosis is well established, yet their significance in early-stage EGFR-mutant lung adenocarcinoma remains unclear. While outcomes for early-stage lung cancer are generally better than those of late-stage disease, recurrence remains a significant challenge. This study investigates the prognostic value of TLSs and their molecular characteristics in early-stage EGFR-mutant lung adenocarcinoma. METHODS: TLSs were identified in tumor samples using multiplex immunohistochemistry (IHC), and their density was quantified. The PD-L1 tumor proportion score (TPS) and TLS density were analyzed for associations with disease-free survival (DFS). Gene expression profiling was performed to compare tumor microenvironment signatures between high- and low-TLS-density groups. RESULTS: High TLS density correlated with significantly longer DFS (43 vs. 20.5 months, p = 0.0082). No relationship was found between TLS density and PD-L1 TPS or EGFR mutation subtype. Transcriptomic analysis revealed upregulated immune response genes in the high-TLS-density group, including those involved in T and B cell activation. Low-TLS-density tumors exhibited gene signatures promoting tumor growth, such as cell cycle and WNT pathway activation. CONCLUSIONS: In summary, TLS density is a potential prognostic biomarker for DFS in early-stage EGFR-mutant lung adenocarcinoma, independent of PD-L1 TPS or EGFR mutation subtype. Enhanced immune activation in high-TLS-density tumors highlights TLSs as a potential target for improving outcomes in these patients.