Hepatitis B virus infection and risk of gastric cancer: a systematic review and meta-analysis.

Hepatitis B virus (HBV) infection is a well-established risk factor for hepatocellular carcinoma. Recent studies have also suggested a higher risk of several extrahepatic cancers in patients with chronic HBV infection, including gastric cancer, even though the results are somewhat inconsistent. The current study was conducted to comprehensively investigate whether patients with HBV infection are at a higher risk of incident gastric cancer compared with individuals without HBV infection using systematic review and meta-analysis technique. Systemic literature review was conducted using EMBASE and MEDLINE database up to December 2019. Eligible studies had to be cohort studies that consisted of one group of patients with HBV infection and another group of individuals without HBV infection. Relative risk of incident gastric cancer between the groups must be reported. Point estimates and standard errors from each eligible study were combined together using the generic inverse variance method of DerSimonian and Laird. A total of 36,812 articles were identified. After two rounds of review, five articles with six cohorts of 120,995 HBV infected patients were included into the meta-analysis. The pooled analysis found that patients with HBV infection had a significantly higher risk of incident gastric cancer than individuals without HBV infection with the pooled risk ratio of 1.49 (95% CI, 1.20 - 1.85; I2=38%). A significantly increased risk of incident gastric cancer among patients with chronic HBV infection was observed in this systematic review and meta-analysis.