This study aims to evaluate the clinical value of circulating tumor DNA (ctDNA) as a minimally invasive biomarker for monitoring treatment response and guiding systemic therapy in patients with gastric or gastroesophageal junction adenocarcinoma. Gastric cancer is often diagnosed at an advanced stage and shows substantial biological heterogeneity. Current treatment decisions mainly rely on imaging and clinical assessment, which may not reflect early molecular changes or minimal residual disease. Circulating tumor DNA, released from tumor cells into the bloodstream, can provide real-time information on tumor burden and treatment response through simple blood sampling. This is a prospective, open-label, phase II exploratory study conducted at a single center. Patients will be enrolled into three clinical cohorts according to their treatment stage: (1) neoadjuvant or conversion therapy cohort, (2) adjuvant therapy cohort after curative surgery, and (3) advanced or metastatic disease cohort receiving systemic therapy. Blood samples for ctDNA analysis will be collected before treatment and at predefined time points during treatment. The study will assess whether changes in ctDNA levels, including ctDNA clearance or reduction, are associated with treatment response, recurrence risk, and survival outcomes. In selected validation phases, treatment strategies may be adjusted based on ctDNA results, while all treatments remain within standard guideline-recommended regimens. The results of this study may help determine whether ctDNA can be used as a practical tool to improve treatment monitoring and support more personalized management of gastric cancer.
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Objective Response Rate (ORR)
Timeframe: Up to 24 months