Risk of Gastric Adenocarcinoma After Eradication of Helicobacter pylori.

[BACKGROUND & AIMS] Helicobacter pylori infection of the stomach is the main risk factor for gastric noncardia adenocarcinoma; however, less is known on how eradication of H pylori influences the risk of this tumor over time, particularly in Western populations. The aim of this study was to delineate how the risk of gastric noncardia adenocarcinoma develops over time after H pylori eradication treatment in a Western population compared with the background population.

[METHODS] This population-based cohort study included all adults having received H pylori eradication treatment between 1995 and 2019 in any of the Nordic countries (Denmark, Finland, Iceland, Norway, and Sweden). Standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) were calculated by comparing the gastric noncardia adenocarcinoma incidence in the study cohort with the incidence in the background population of the same age, sex, calendar period, and country. Time trends in SIR were assessed using Poisson regression.

[RESULTS] Among 659,592 participants having received H pylori eradication treatment, contributing 5,480,873 person-years at risk, 1311 developed gastric noncardia adenocarcinoma. During up to 24 years of follow-up, the SIR was initially higher than the background population (SIR, 2.27; 95% CI 2.10-2.44, 1-5 years after treatment), and then gradually decreased over time and approached the level of the background population from 11 years after treatment (SIR, 1.11; 95% CI 0.98-1.27, 11-24 years after treatment).

[CONCLUSION] This study revealed a decreasing incidence of gastric noncardia adenocarcinoma after H pylori eradication treatment in 5 Western populations. The risk became virtually similar to the background population from 11 years after treatment.