Infiltrating and peripheral immune cell analysis in advanced gastric cancer according to the Lauren classification and its prognostic significance

Background The correlation between immune cells and the Lauren classification subtypes and their prognostic impact in advanced gastric cancer (AGC) are unknown. Methods Circulating natural killer (NK) cells, CD4(+) and CD8(+) T cells, regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs) were quantified in peripheral blood mononuclear cells (PBMCs) from 67 patients with untreated AGC enrolled in the PRODIGE 17-ACCORD 20 trial. CD56(+) cells (NK), CD8(+), and FoxP3(+) (Treg) tumor-infiltrating lymphocytes (TILs) were assessed in tumor samples. Results Circulating NK and Treg proportions were significantly lower in patients with diffuse/mixed-type AGC (n = 27) than those with intestinal type (n = 40; median 6.3% vs 11.5%; p = 0.02 and median 3.3% vs 5.2%; p = 0.03, respectively). Proportions of circulating MDSC, CD4(+) and CD8(+) T cells were not associated with one pathological type. Among tumor-infiltrating cells, CD8(+) T cells, but not NK or FoxP3(+) cells, were significantly lower in diffuse/mixed-type AGC (median 21 vs 59 cells/field; p = 0.009). Patients with high circulating NK cell counts (> 17%) had a better overall survival than those with < 17% (HR 0.40; 95% CI [0.15-1.06]; p = 0.04). Patients with high CD8(+) TIL counts (> 31 cells/field) had significantly longer overall survival (HR 0.44; 95% CI [0.21-0.92]; p = 0.02). The prognostic value of CD8(+) TILs was maintained after adjustment for confounding factors, including the Lauren classification (HR = 0.42; 95% CI [0.18-0.96]; p = 0.039). Conclusion Diffuse/mixed-type AGC has lower rates of CD8(+) TILs and circulating NK cells and Tregs than the intestinal type. This cold tumor phenotype may be associated with a worse outcome.