Association between proton pump inhibitors after percutaneous coronary intervention and risk of gastric cancer

BACKGROUND: Previous studies showing an association between chronic use of proton pump inhibitor (PPI) and gastric cancer are limited by confounding by indication. This relationship has not been studied in patients receiving PPI for prophylaxis, such as those undergoing percutaneous coronary intervention (PCI). METHOD: This was a retrospective cohort study including 14 hospitals under the Hospital Authority of Hong Kong between 1 January 2004 and 31 December 2017. Participants were patients who underwent first-ever PCI, were not on PPI prescription within 30 days before admission for PCI, had no known malignancy and survived for 365 days after PCI. Propensity score matching was used to balance baseline characteristics and other prescription patterns. The primary outcome was diagnosis of gastric cancer made >365 days after PCI as a time-to-first-event analysis. The secondary outcome was death from gastric cancer. RESULTS: Among the 13 476 patients (6738 pairs) matched by propensity score, gastric cancer developed in 17 (0.25%) PPI users and 7 (0.10%) PPI non-users after a median follow-up of 7.1 years. PPI users had a higher risk of gastric cancer (HR 3.55; 95% CI 1.46 to 8.66, p=0.005) and death from gastric cancer (HR 4.18; 95% CI 1.09 to 16.08, p=0.037), compared with non-users. The association was duration-dependent and patients who took PPI for ≥365 days were at increased risk. CONCLUSIONS: Chronic use of PPI was significantly associated with increased risk of gastric cancer and death from gastric cancer in patients for whom it was prescribed as prophylaxis. Physicians should judiciously assess the relevant risks and benefits of chronic PPI use before prescription.