Clinical outcomes of Epstein–Barr virus (EBV)-associated metastatic and locally advanced unresectable gastric cancers (GCs) in patients receiving first-line fluoropyrimidine and platinum (FP) doublet chemotherapy

Background: Epstein–Barr virus-associated gastric cancer (EBVaGC) is a distinct molecular subgroup showing excellent outcomes after surgery for localized disease. Prominent immune cell infiltration in EBVaGC reflects the immunogenicity of Epstein–Barr virus (EBV) and, as suggested by some investigators, responsiveness to immune checkpoint inhibitors in the palliative setting. However, few data are available on the prevalence, clinical characteristics, and prognosis of EBVaGC patients receiving palliative cytotoxic chemotherapy. Methods: In this retrospective study, we identified 1061 patients with metastatic, recurrent, or locally advanced unresectable gastric cancer (GC) who started first-line fluoropyrimidine/platinum (FP) doublet chemotherapy with or without trastuzumab from January 2015 to August 2018. For 766 patients with available tumor tissue, the presence of EBV in cancer cells was evaluated by EBV-encoded RNA in situ hybridization and correlated with clinical characteristics and treatment outcomes. Results: Among the patients evaluated (n = 766), 40 (5.0%) were EBV-positive. EBVaGC was associated with male sex (p = 0.009) and lower neutrophil–lymphocyte ratio (NLR < 2.46, p = 0.03). Efficacy of first-line FP chemotherapy, in terms of response rate ad progression-free survival (PFS), did not differ between EBVaGC and EBV-negative GC (overall response rate: 53.8% vs. 51.8%, p = 0.99; median PFS: 6.4 vs. 6.7 months, p = 0.90). However, overall survival tended to be better with EBVaGC than EBV-negative GC (16.4 vs. 14.0 months, p = 0.07). Conclusions: EBVaGC accounted for 5% of metastatic/unresectable GCs. While EBVaGC was not associated with better response to or PFS following first-line cytotoxic chemotherapy, it showed a trend toward better overall survival.