Helicobacter pylori (H. pylori) has been shown to be a causal factor of gastric cancer in cohort studies and animal models. Meta-analysis of case-control studies nested within prospective cohorts showed that H. pylori infection was associated with a 5.9-fold increased risk of non-cardia gastric cancer. Prospective cohort studies showed that gastric cancer developed in 1-4% of H. pylori-infected subjects. Gastric cancer was successfully induced in Mongolian gerbils and insulin-gastrin (INS-GAS) transgenic mice after inoculation of H. pylori. Meta-analysis of randomized control trials also showed that eradication of H. pylori may reduce the risk of gastric cancer. However, there are several concerns regarding the widespread use of antibiotics to prevent gastric cancer, including the emergence of antibiotic resistance and the perturbation of gut microbiota after H. pylori eradication. Recent studies showed that eradication of H. pylori resulted in an increase in the bacterial diversity and restoration of the relative abundance of other bacteria to levels similar to H. pylori non-infected subjects in the gastric microbiota. The administration of antibiotics may also alter the composition of intestinal microbiota. The α-diversity and β-diversity of fecal microbiota are significantly altered immediately after H. pylori eradication but are gradually restored to levels similar to those before therapy. Yet, the rate of recovery varies with regimens. The diversity was restored at week 8 after triple therapy but was not yet fully recovered at 1 year after concomitant and quadruple therapies. Some studies showed that supplementation of probiotics may reduce the dysbiosis during H. pylori eradication therapy. Although some earlier studies showed high levels of macrolide resistance after triple therapy, recent studies showed that the increased antibiotic resistance rate may be restored 2-12 months after eradication therapy. These results collectively provide evidence of the long-term safety of H. pylori eradication. Yet, more prospective cohort studies and randomized trials are warranted to assess the efficacy and long-term safety of H. pylori eradication for gastric cancer prevention.
Keywords: H. pylori; efficacy; eradication; gastric cancer prevention; safety; screening.