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 (Pinteraction = .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.