ABO blood group, Helicobacter pylori seropositivity, and risk of pancreatic cancer: a case-control study.

Carriage of a non-O ABO blood group and colonization by Helicobacter pylori are thought to be risk factors for pancreatic cancer. We examined these associations in a population-based case-control study of 373 case patients and 690 control subjects frequency matched on sex and age. Control subjects were selected by random-digit dialing. Seropositivity for H pylori and its virulence protein CagA was determined by enzyme-linked immunosorbent assay (ELISA). Increased risk of pancreatic cancer was associated with non-O blood group (adjusted odds ratio [OR] = 1.37, 95% confidence interval [CI] = 1.02 to 1.83, P = .034) and CagA-negative H pylori seropositivity (OR = 1.68, 95% CI = 1.07 to 2.66, P = .025), but no association was observed for CagA seropositivity (OR = 0.77, 95% CI = 0.52 to 1.16). An association between pancreatic cancer risk and CagA-negative H pylori seropositivity was found among individuals with non-O blood type but not among those with O blood type (OR = 2.78, 95% CI = 1.49 to 5.20, P = .0014; OR = 1.28, 95% CI = 0.62 to 2.64, P = .51, respectively). This study demonstrates an association between pancreatic cancer and H pylori colonization, particularly for individuals with non-O blood types.