Associations between hepatitis B virus exposure and the risk of extrahepatic digestive system cancers: A hospital‐based, case–control study (SIGES).

Objectives: This case–control study was aimed to investigate associations between HBV infection and extrahepatic digestive system cancers. Methods: The patients of gastric, small intestinal, colonic, rectal, anal, biliary tract, and pancreatic cancers were retrospectively collected between 2016.5 and 2017.12. Simultaneously, the healthy controls were collected from the health check‐up registry, and cancer‐free status was confirmed based on medical records. Propensity score matching was performed to reduce bias. Multinomial logit model and conditional logistic regression model were used to assess the risk of individual cancer according to HBV serological markers and classifications. Results: Totally, 4748 patients involving seven cancers, and 57,499 controls were included. After matching, HBsAg was associated with increased risk of gastric cancer (aOR = 1.39, 95% CI: 1.05–1.85), and anti‐HBs served as a protective factor for gastric (aOR = 0.72, 95% CI: 0.61–0.85), colonic (aOR = 0.73, 95% CI: 0.60–0.89), rectal (aOR = 0.73, 95% CI: 0.63–0.85), and pancreatic (aOR = 0.58, 95% CI: 0.42–0.82) cancers. Compared to subgroups with non‐infection and vaccination status, inactive HBsAg carriers and active HBV infection subgroup were correlated with gastric carcinogenesis (aOR = 1.41, 95% CI: 1.03–1.93). However, no clear association was found between HBV infection and other cancers. Conclusions: HBV infection was potentially associated with an increased risk of gastric cancer. The development mechanism of HBV‐associated gastric cancer needs to investigate further. [ABSTRACT FROM AUTHOR]