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

Abstract

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.

Figure 1

Forest plot of the odds ratio (OR) of pancreatic cancer according to Helicobacter pylori seropositivity. The solid squares are centered on the point estimate from each study, and the horizontal line through each square indicates the 95% confidence interval (CI) for the study estimate. The area of each square represents the weight of the study in the meta-analysis. The center of each diamond indicates the inverse variance-weighted summary estimate of the effect size; the horizontal tips represent the 95% confidence interval; the area represents the combined areas of the solid squares included in the summary. The vertical dashed line is at the center of the total pooled odds ratio (OR = 1.65). The seven studies show little heterogeneity (Q statistic P value = .93). All of the studies except Kosunen et al. (15) ascertained seropositivity for H pylori. Kosunen et al. (15) examined incidence of pancreatic cancer in a cohort of individuals colonized by H pylori. In this cohort, 4137 of the total 18 012 carriers had successful H pylori eradication, and in the figure, the odds ratio and confidence interval for this study represent noneradication of H pylori. Fixed-effects inverse-weighting meta-analysis summary calculations on the log odds ratios (18) for the diamonds in the figure were performed in Excel.