Role of circulating tumour DNA in gastric cancer: a review

Circulating tumour DNA (ctDNA) represents an emerging liquid biopsy tool with significant clinical utility in gastric cancer detection, monitoring and prognostication. Multicancer early detection blood tests achieve 66.7% sensitivity for advanced disease and up to 81% for early-stage detection using methylation-based assays. ctDNA predicts treatment response approximately 8 weeks earlier than radiographic imaging, with patients achieving ctDNA negativity after therapy demonstrating substantially improved overall survival (73% vs 34%). For minimal residual disease detection, tumour-informed ctDNA assays identify recurrence 4–6 months before imaging with 95.5% specificity and 85.7% sensitivity, enabling early intervention in high-risk patients. Notably, ctDNA captures tumour heterogeneity and clonal evolution more comprehensively than tissue biopsy alone, identifying resistance-associated mutations and targetable alterations that guide sequential treatment decisions. Integration of ctDNA with tissue biopsy improves molecular concordance from 45% to 87.5%, providing a more complete tumour landscape assessment. These findings support ctDNA as a transformative tool for precision-guided oncologic management and adaptive therapeutic decision-making throughout the gastric cancer patient journey.