• Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
• Infections and Cancer Epidemiology; Research Program Infection, Inflammation and Cancer, German Cancer Research Center (DKFZ), Heidelberg, Germany.
• Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA. freedmanne@mail.nih.gov.

Helicobacter has been suggested to play a possible role in hepatitis, gallstones, and hepatobiliary tumours. We assessed whether seropositivity to 15 H. pylori proteins was associated with subsequent incidence of 74 biliary tract and 105 liver cancer cases vs. 357 matched controls in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO). Odds ratios and 95% confidence intervals were computed by conditional logistic regression after adjustment for known hepatobiliary cancer risk factors. H. pylori seropositivity was not associated with either biliary tract (1.76, 0.90-3.46) or liver cancer (0.87, 0.46-1.65). CagA seropositivity was associated with both endpoints, although the latter association was not statistically significant (biliary tract: 2.16, 1.03-4.50; liver cancer: 1.96, 0.98-3.93) and neither association was statistically significant after correcting for multiple comparisons. Together, these results suggest possible associations between H. pylori and hepatobiliary cancer and suggest the value of future studies investigating the association.Trial registration number: NCT00339495.