Estimating the prevalence of Epstein-Barr virus in primary gastric lymphoma: a systematic review and meta-analysis.

The stomach is a common site for extranodal non-Hodgkin's lymphoma. While Helicobacter pylori (H. pylori) is the main established risk factor for primary gastric lymphoma, a fraction could be aetiologically associated with Epstein-Barr virus (EBV), a known haematolymphoid carcinogen. We systematically searched five databases from 1 January 1990 until 31 May 2022 for studies reporting EBV prevalence in gastric lymphoma tumour tissue by in-situ hybridisation (ISH) for EBV-encoded small RNA (PROSPERO CRD42020164473). We included representative series of more than five gastric lymphoma cases. Pooled prevalence and corresponding 95% confidence intervals (CI) of EBV in gastric tumour cells were calculated for two major gastric B-cell lymphoma types, mucosa-associated lymphoid tissue (MALT) lymphoma and diffuse large B-cell lymphoma (DLBCL). When available, we also extracted data on H. pylori prevalence and survival by EBV status. We found ten studies including 194 cases of gastric MALT lymphoma and 11 studies including 643 cases of gastric DLBCL. EBV prevalence was 2.2% (95% CI: 0.5-13.3) in gastric MALT lymphoma and 11.0% (95% CI: 5.2-20.0) in gastric DLBCL. In a subset of studies, the prevalence of H. pylori was higher in gastric MALT lymphoma (51/69) compared to gastric DLBCL (62/102). Overall, our findings suggest that EBV is rarely seen in MALT lymphoma but is associated with around 10% of gastric DLBCL, similar to the proportion observed at other primary sites. EBV-related lymphoma adds a small number of cases to the burden of cancer that could be prevented by the future development of a vaccine against EBV.