Abstract
BACKGROUND: Gastric cancer remains a major global health burden with high mortality due to late-stage diagnosis and limited treatment efficacy. Emerging evidence demonstrates that the tumor microenvironment, particularly immune cell infiltration patterns and hypoxia-induced immunosuppression, plays a critical role in cancer progression. This study investigates the spatial immune cell architecture in postoperative gastric cancer tissues to identify prognostic biomarkers and guide personalized immunotherapy strategies. AIM: To investigate the spatial distribution pattern, density, and proportional features of important immune cells in the tumor microenvironment following radical gastrectomy for gastric cancer, assess their relationships with patients' 5-year overall survival (OS) and recurrence-free survival following surgery, and provide an immunological foundation for prognostic assessment. METHODS: A total of 112 patients with stage I-III gastric cancer who underwent R0 resection between June 2018 and June 2020 were included retrospectively. Paraffin-embedded specimens of postoperative cancer tissues and adjacent tissues were collected. The multicolor immunohistochemistry technique was used, and pan-cytokeratin staining was performed synchronously with 4,6-diamidino-2-phenylindole nuclear staining. The sections were scanned by the Vectra Polaris™ full-spectrum imaging system, and cell phenotype identification and spatial localization analysis were performed via InForm(®) 2.6 software. The independent prognostic value of OS/disease-free survival and immunological markers was assessed (tumor-node-metastasis stage, Lauren classification), and the Kaplan-Meier survival curve was used to analyze the survival differences between the high/low immune infiltration groups (log-rank test). RESULTS: The density of CD8+ T cells in the invasion margin area (median: 248.5/mm(2)) was significantly greater than that in the tumor core area (108.3/mm(2), P < 0.001). The 5-year OS rate was high in patients with a high CD8+ density (> 220/mm(2); 68.2%), low-density group: 42.1%, P = 0.003. An independent correlation between extended disease-free survival and a CD8+/forkhead box protein 3+ (FoxP3+) ratio > 2.5 was found [hazard ratio (HR) = 0.47, 95% confidence interval (CI): 0.29-0.76]. The risk of death was greater for those with a fraction of programmed death ligand 1+ tumor cells > 10% (HR = 2.15, 95%CI: 1.32-3.51). The enrichment of CD68+CD163+ M2 macrophages in the core area of the tumor predicted an increased risk of recurrence (HR = 1.72, P = 0.018). An immune prognosis scoring system was constructed on the basis of least absolute shrinkage and selection operator (regression, integrating the density of the CD8+ marginal zone, the CD8+/FoxP3+ ratio, and the 5-year OS prediction area under the curve was 0.81 (95%CI: 0.74-0.88). CONCLUSION: The spatial distribution pattern of immune cells in the tumor microenvironment following gastric cancer surgery and the percentages of particular subgroups (programmed death ligand 1+ and CD8+/FoxP3+ tumor cells) are independent predictors of long-term survival.