Background: Epstein–Barr virus-associated gastric cancer (EBVaGC) represents a distinct molecular subgroup with potential responsiveness to immunotherapy approved for programmed death-ligand 1 (PD-L1)-positive gastric cancer. This retrospective study aimed to assess the prevalence and association between EBVaGC and PD-L1 positivity among patients with gastric adenocarcinoma treated at a university hospital in Southern Thailand from January 2017 to October 2023. Methods: The EBV status of the patients and PD-L1 expression were determined using in situ hybridization and immunohistochemistry, respectively. Results: The prevalence of EBVaGC was 4.5% among 132 patients, whereas 9.1% of patients exhibited a PD-L1 combined positive score (CPS) of ≥1, with no significant association observed between them. EBVaGC was more prevalent in males, non-antral tumors, diffuse/mixed histologic subtypes, and poorly differentiated tumors. Median overall survival for patients with EBVaGC and PD-L1 CPS ≥ 1 was 9.48 and 14.19 months, respectively, compared with 10.32 and 9.79 months for those with non-EBVaGC (hazard ratio: 1.24; 95% CI: 0.50–3.04;p= 0.645) and PD-L1 CPS < 1 (hazard ratio: 0.82; 95% CI: 0.40–1.69;p= 0.590), respectively. Conclusions: Our findings revealed a low prevalence of EBVaGC and PD-L1 positivity in Thailand, with no significant association or survival impact observed. These findings highlight the regional variation in these biomarkers and support EBV as an independent biomarker from PD-L1. However, further research, particularly studies evaluating immunotherapy outcomes, is warranted to clarify the predictive and clinical significance of EBV in gastric cancer.
背景：爱泼斯坦-巴尔病毒相关胃癌（EBVaGC）作为一种独特的分子亚型，对已获批用于程序性死亡配体1（PD-L1）阳性胃癌的免疫疗法可能具有治疗反应性。本研究旨在回顾性分析2017年1月至2023年10月期间泰国南部某大学医院收治的胃腺癌患者中EBVaGC与PD-L1阳性率的流行情况及两者关联性。方法：分别采用原位杂交和免疫组织化学技术检测患者EBV状态及PD-L1表达水平。结果：在132例患者中，EBVaGC的患病率为4.5%，而PD-L1综合阳性评分（CPS）≥1的患者占9.1%，两者未发现显著相关性。EBVaGC在男性、非胃窦肿瘤、弥漫型/混合型组织学亚型及低分化肿瘤中更为常见。EBVaGC患者与PD-L1 CPS≥1患者的中位总生存期分别为9.48个月和14.19个月，而非EBVaGC患者（风险比：1.24；95% CI：0.50-3.04；p=0.645）和PD-L1 CPS<1患者（风险比：0.82；95% CI：0.40-1.69；p=0.590）的中位总生存期分别为10.32个月和9.79个月。结论：本研究发现泰国地区EBVaGC与PD-L1阳性率较低，且未观察到显著相关性或生存影响。这些发现揭示了这些生物标志物的地域差异性，并支持EBV作为独立于PD-L1的生物标志物。然而，仍需进一步研究，特别是评估免疫治疗疗效的相关研究，以明确EBV在胃癌中的预测价值及临床意义。
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