Helicobacter pylori-modulated host immunity in gastric cancer patients with S-1 adjuvant chemotherapy

Background Paradoxically, Helicobacter pylori-positive (HP+) advanced gastric cancer patients have a better prognosis than those who are HP-negative (HP-). Immunologic and statistical analyses can be used to verify whether systemic mechanisms modulated by HP are involved in this more favorable outcome. Methods A total of 658 advanced gastric cancer patients who underwent gastrectomy were enrolled. HP infection, mismatch repair, programmed death-ligand 1 (PD-L1) and CD4/CD8 proteins, and microsatellite instability were analyzed. Overall survival (OS) and relapse-free survival (RFS) rates were analyzed after stratifying clinicopathological factors. Cox proportional hazards regression analysis was performed to identify independent prognostic factors. Results Among 491 patients that were analyzed, 175 (36%) and 316 (64%) patients were HP+ and HP-, respectively. Analysis of RFS indicated an interaction of HP status among the subgroups for S-1 dose (P-interaction = .049) and PD-L1 (P = .02). HP+ patients in the PD-L1(-) group had statistically higher 5-year OS and RFS than HP- patients (81% vs 68%; P = .0011; hazard ratio [HR] = 0.48, 95% confidence interval [CI] = 0.303 to 0.751, and 76% vs 63%; P = .001; HR = 0.508, 95% CI = 0.335 to 0.771, respectively). The 5-year OS and RFS was also statistically higher for HP+ compared with HP- patients in the "PD-L1(-) and S-1-r educed" group (86% vs 46%; P = .001; HR = 0.205, 95% CI = 0.07 to 0.602, and 83% vs 34%; P = .001; HR = 0.190, 95% CI = 0.072 to 0.498, respectively). Thus, HP status was identified as one of the most potentially important independent factors to predict prolonged survival. Conclusion This retrospective study suggests that an HP-modulated host immune system may contribute to prolonged survival in the absence of immune escape mechanisms of gastric cancer.