Prognostic value of intratumoral natural killer cells in gastric carcinoma

Natural killer (NK) cells are a group of effector cells that act nonspecifically against tumor cells. The correlation between intratumoral NK cell infiltration and clinicopathologic features remains unclear.The authors selected 146 patients with gastric carcinoma who underwent gastrectomy at Kagoshima University Hospital between 1985-1995. Immunohistochemical staining with the CD57 antibody was performed for the evaluation of NK cell infiltration. A total of 25 areas containing CD57 positive cells were selected and the number of NK cells were counted (magnification, x200). The patients were divided into 2 groups: patients with a high level of NK infiltration (n = 39) (25 NK cells/25 high-power fields [HPF]) and patients with a low level of NK infiltration (n = 107) (25 NK cells/25 HPF). Intratumoral lymphocytic infiltration also was counted in 25 areas at a magnification of x200. Patients were classified into a high infiltrating lymphocyte (IL) group (n = 69) (150 cells/HPF) and a low IL group (n = 77) (150 cells/HPF). The Kaplan-Meier curve was used to analyze surgical outcome. Multivariate analyses were performed to evaluate prognostic factors.Patients with a high level of NK infiltration had a higher rate of early gastric carcinoma, fewer metastases to the lymph nodes (P0.01), and less lymphatic invasion (P0.05) than patients with a low level of NK infiltration. NK cell infiltration also was found to correlate with depth of invasion, clinical stage, and venous invasion. There was no correlation between NK cells and lymphocytic infiltration (P = 0.07; correlation coefficient = 0.15). The 5-year survival rate of patients with a high rate of NK infiltration was 78%, which was significantly better than that of patients with a low level of NK infiltration (P0.01). Multivariate analysis did not show NK cell infiltration to be a significant prognostic factor. Combination analysis of the number of NK cells and lymphocytic infiltration was shown to be an independent prognostic factor (P = 0.02; hazard ratio = 1.32).Patients with a high level of NK infiltration were found to have a better prognosis than those with a low level of NK infiltration. Combination analysis with lymphocytic infiltration may provide useful information regarding the immunologic condition of patients with gastric carcinoma.