Neutrophil extracellular traps predict sensitivity to neoadjuvant chemotherapy combined with immunotherapy in locally advanced gastric cancer.

BACKGROUND: Neutrophil extracellular traps (NETs) are associated with an immunosuppressive tumor microenvironment and may influence the efficacy of immune-based therapies. However, their role in neoadjuvant chemotherapy combined with immunotherapy (NACI) for locally advanced gastric cancer (LAGC) remains unclear. AIM: To investigate the prognostic and predictive value of NET density in LAGC patients undergoing NACI. METHODS: We enrolled 31 LAGC patients treated with NACI. NET density was assessed through dual immunofluorescence staining of citrullinated histone H3 and myeloperoxidase in pretreatment biopsy and post-treatment surgical specimens. Patients were stratified into high and low pre-NACI NET groups based on median NET density. Pathological complete response (pCR) and overall response rates were evaluated in relation to NET density. Logistic regression analyses were performed to identify independent predictors of treatment outcomes. Dynamic changes in NET density during NACI were also analyzed. RESULTS: Patients with low pre-NACI NET density demonstrated significantly higher rates of pCR (40% vs 6%, P = 0.037) and overall response (53% vs 12%, P = 0.023) compared to those with high NET density. Low pre-NACI NET density and higher programmed death protein ligand 1 expression were identified as independent protective factors for achieving pCR and better response rates. NACI increased NET density; however, this increase was primarily observed in non-pCR and nonresponder groups. Patients in the pCR and responder groups showed stable NET density before and after treatment. Higher post-NACI NET density was associated with poorer respond to NACI. High post-NACI NET density was associated with increased infiltration of immunosuppressive FOXP3(+) T regulatory cells (P = 0.025) and CD68(+) macrophages (P = 0.038). CONCLUSION: Pre-NACI NET density serves as a prognostic and predictive biomarker for NACI efficacy in LAGC patients. Low pretreatment NET density is associated with favorable outcomes, while increased post-treatment NET density correlates with poorer response. Targeting NET formation may represent a novel therapeutic strategy to enhance NACI efficacy in LAGC.