Helicobacter pylori Seropositivity, ABO Blood Type, and Pancreatic Cancer Risk From 5 Prospective Cohorts

Helicobacter pylori infection may be a risk factor for pancreatic cancer, particularly infection by strains without the cytotoxin-associated gene A (CagA) virulence factor. Non-O blood type is a known risk factor for pancreatic cancer, and H. pylori gastric colonization occurs largely from bacterial adhesins binding to blood group antigens on gastric mucosa. METHODS: We included 485 pancreatic cancer cases and 1,122 matched controls from 5 U.S. prospective cohorts. Prediagnostic plasma samples were assessed for H. pylori and CagA antibody titers. Conditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for pancreatic cancer. ABO blood type was assessed using genetic polymorphisms at the ABO gene locus or self-report. RESULTS: Compared with H. pylori–seronegative participants, those who were seropositive did not demonstrate an increased risk of pancreatic cancer (OR 0.83, 95% CI 0.65–1.06). This lack of association was similar among CagA-seropositive (OR 0.75, 95% CI 0.53–1.04) and -seronegative (OR 0.89, 95% CI 0.65–1.20) participants. The association was also similar when stratified by time between blood collection and cancer diagnosis (P-interaction = 0.80). Consistent with previous studies, non-O blood type was associated with increased pancreatic cancer risk, but this increase in risk was similar regardless of H. pylori seropositivity (P-interaction = 0.51). DISCUSSION: In this nested case-control study, history of H. pylori infection as determined by H. pylori antibody serology was not associated with pancreatic cancer risk, regardless of CagA virulence factor status. The elevated risk associated with non-O blood type was consistent in those with or without H. pylori seropositivity.