medwireNews: Research shows that Epstein-Barr virus (EBV) positivity in gastric tumor cells is associated with improved prognosis.
A study, published in Gut, found that EBV-positive gastric cancer tends to have a low tumor-node-metastasis (TNM) stage, and even after adjusting for this, it still conferred a survival advantage over EBV-negative tumors.
The researchers, led by Constanza Camargo (National Cancer Institute, Rockville, Maryland, USA), analyzed data on 4599 patients with invasive gastric cancer diagnosed between 1976 and 2010 in Asia, Europe, and Latin America, of whom 375 (8.2%) had EBV-positive tumors. Over a median follow up of 3 years, 2247 (49%) patients died.
TNM stage was a strong predictor for mortality, with each unit change associated with a 21% reduction in the odds for survival. And, each component of the TNM stage was inversely associated with tumor EBV positivity.
In multivariate analyses, after adjusting for stage and other confounders, EBV positivity was associated with a 28% decreased risk for mortality, with a median survival time of 8.5 years among patients with EBV-positive tumors and 5.3 years among those with EBV-negative tumors.
In addition, the authors note that advanced stage, older age, and less differentiation were all associated with worse prognosis. And, tumors localized in the cardia were associated with higher mortality than non-cardia tumors, but lower mortality compared with tumors in overlapping subsites or the surgical stump.
Around 9% of gastric carcinomas have EBV in the tumor cells, but until now it has not been clear how the virus influences clinical progression, the researchers explain.
They say that their findings add support to the idea that EBV-positive gastric cancer should be considered a separate clinical entity.
"EBV-positive gastric cancer exhibits uniform presence of monoclonal viral episomes in the tumour cells, implying the presence of EBV at the time of initial transformation and its requirement for maintenance of the transformed phenotype," say Camargo and colleagues.
They add: "EBV-positive gastric cancer also displays distinct clinical, genetic and demographic features as compared to EBV-negative cancer."
Further research is needed to discern the mechanisms that underlie the association between EBV-positivity and survival, they conclude.
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