EBV tumor positivity was associated with lower tumor stage and longer survival.
In a small but significant percentage (9%) of gastric cancers, tumor cells contain Epstein-Barr virus (EBV). To assess whether EBV positivity is associated with cancer outcomes, investigators pooled data on 4599 patients with invasive gastric cancer from 13 case series.
Median follow-up was 3.0 years. The prevalence of EBV-positive cancer was 8.2%. In multivariate analysis, EBV positivity was associated with lower tumor stage (odds ratio, 0.79 per unit change in stage; 95% confidence interval, 0.69–0.91). In unadjusted regression analysis, higher tumor stage was associated with higher mortality, with hazard ratios of 3.1 for stage II, 8.1 for stage III, and 13.2 for stage IV when compared with stage I. Median survival was higher in patients with EBV-positive tumors than in patients with EBV-negative tumors (8.5 years vs. 5.3 years; P=0.0006). After adjusting for stage and other potential confounders, EBV positivity was associated with lower mortality (HR, 0.72; 95% CI, 0.61–0.86). Heterogeneity among studies was low.
Comment: Findings from this large study support previous data showing a better prognosis for gastric cancers that contain Epstein-Barr virus. However, because these results are from a pooled analysis of case series rather than a meta-analysis of published studies, it is possible that inclusion of other case series could affect the results. In addition, results are limited by the lack of data on treatment. Nevertheless, by focusing on these studies, the investigators were able to evaluate a relatively homogeneous dataset, minimizing confounding between series. As the authors note, the mechanism for improved outcomes with EBV positivity requires additional study, as does the possibility that EBV-positive gastric cancer might represent a distinct disease entity.