Proton pump inhibitors and the risk for gastric cancer: possible confounding by serum vitamin B 12

We read with interest the article by Cheung et al 1 reporting an increased risk of gastric cancer with long-term exposure to proton pump inhibitors (PPI) following Helicobacter pylori (HP) eradication. Several recent reports and a meta-analysis have also demonstrated this association.2 3 The present study, using strict exclusion criteria, was able to adjust for the confounding effect of previous HP infection and eradication, demonstrating a PPI exposure-dependent escalating risk for non-cardia gastric cancer (NCGC) in previously infected patients. The authors suggest that the profound acid suppression by PPIs worsens the atrophic gastritis induced by HP infection, …