循环肿瘤DNA（ctDNA）是肿瘤或循环肿瘤细胞释放的游离DNA，含有丰富的肿瘤特异性信息，可作为癌症早期筛查、监测、预后和治疗反应预测的生物标志物。这在目前缺乏高质量筛查、监测和预测方法的胃癌领域尤其有吸引力。胃癌表现出显着的肿瘤异质性，不同亚群之间的遗传和表观遗传特征存在较大差异。甲基化ctDNA具有较高的敏感性和特异性，有助于阐明肿瘤基因分型，有利于制定精准的诊断和治疗策略。此外，大量研究证实了甲基化DNA在预测治疗反应、辅助治疗、耐药评估等方面的独特优势，未来可能用于增强化疗方案的疗效、改善患者的化疗反应，甚至治疗多药耐药。 。然而，甲基化ctDNA存在一些挑战，例如单靶点敏感性和特异性较低、某些胃癌亚型与ctDNA之间的关联性有限、脱靶风险以及缺乏大规模、高质量的临床研究等。研究证据。本综述主要总结了目前胃癌中ctDNA甲基化状态的研究，并将这些发现与胃癌的早期筛查、复发监测和潜在的治疗机会联系起来。随着技术的进步和跨学科研究的深入，ctDNA检测将揭示更多的疾病信息，成为胃癌研究和精准医学治疗的重要基础。

Circulating tumor DNA (ctDNA) is cell-free DNA released by tumors or circulating tumor cells, containing abundant tumor-specific information that can serve as biomarkers for cancer early screening, monitoring, prognosis, and prediction of treatment response. This is particularly attractive in the field of gastric cancer, where high-quality screening, monitoring, and prediction methods are currently lacking. Gastric cancer exhibits significant tumor heterogeneity, with large differences in genetic and epigenetic characteristics among different subgroups. Methylated ctDNA has high sensitivity and specificity, which can help clarify tumor genotyping and facilitate the formulation of precise diagnostic and therapeutic strategies. Furthermore, numerous studies have confirmed the unique advantages of methylated DNA in predicting treatment response, adjuvant therapy, and drug resistance assessment, which may be used in the future to enhance the efficacy of chemotherapy regimens and improve patient chemotherapeutic response, and even treat multidrug resistance. However, there are several challenges associated with methylated ctDNA, such as low sensitivity and specificity at single-target sites, limited association between some gastric cancer subtypes and ctDNA, off-target risks, and the lack of large-scale and high-quality clinical research evidence. This review mainly summarizes current research on the methylation status of ctDNA in gastric cancer and connects these findings to early screening, recurrence monitoring, and potential treatment opportunities for gastric cancer. With advances in technology and the deepening of interdisciplinary research, ctDNA detection will reveal more disease information and become an essential foundation for gastric cancer research and precision medicine treatment.