Associations between gastric cancer risk and virus infection other than Epstein-Barr virus: The protocol of a systematic review and meta-analysis based on epidemiological studies

BACKGROUND: Gastric cancer is one of the infection associated malignancies. In addition to Helicobacter pylori and Epstein-Barr virus (EBV), other oncoviruses might play potential roles in the development of gastric cancer. Associations of oncoviruses other than EBV with gastric cancer risk are aimed to be comprehensively reviewed and assessed in this systematic review and meta-analysis, to identify any potentially causative oncovirus. It might be informative to identify or deny certain oncoviruses which are candidates of risk factor for gastric cancer. To our knowledge, there is no comprehensive review on oncoviruses other than EBV associated with gastric cancer risk. Positive findings might be helpful to suggest further mechanism investigation and high-risk subpopulation recommendation. METHODS: PubMed database will be searched up to Dec 31, 2018. The studies, compared the positivity of any oncovirus other than EBV between cases with histologically proven gastric cancer and healthy or nonmalignant controls, are eligible. The detection of oncovirus either in tissue or blood is acceptable. Selection, quality assessment (Newcastle-Ottawa Scale), and data extraction of eligible studies will be performed by 2 independent reviewers. Pooled prevalence of any oncovirus will be combined by meta-analysis for rate. Pooled odds ratio between gastric cancer cases and controls will be estimated by meta-analysis. Heterogeneity and publication bias will be tested. In sensitivity analysis, the leave-one-out method and exclusion of low power studies will be applied where applicable. RESULTS: This review was not submitted for any ethical approval due to the literature-based nature. The results will be published in a journal and presented at conferences for academic purposes. Registration number was CRD42015029703 in the PROSPERO International Prospective Register of Systematic Reviews. CONCLUSIONS: To our knowledge, there is no comprehensive review on oncoviruses other than EBV associated with gastric cancer risk. Positive findings might be helpful to suggest further mechanism investigation and high-risk subpopulation recommendation.