This prospective observational study will enroll adults with gastric or gastroesophageal junction adenocarcinoma who achieve pathological complete response or major pathological response after neoadjuvant therapy and R0 gastrectomy. The study will evaluate whether postoperative circulating tumor DNA-based molecular residual disease status can identify participants at increased risk of recurrence despite a favorable pathological response. All postoperative treatment decisions will be made by the treating clinicians according to routine care and will not be assigned by the study. Tumor-informed ctDNA-MRD testing will be performed longitudinally, and results will not be used to alter treatment. Participants will be followed for disease-free survival, overall survival, recurrence detection, and adverse events.
Age 18 to 75 years.
Histologically confirmed gastric or gastroesophageal junction adenocarcinoma.
Completion of preoperative neoadjuvant therapy followed by R0 gastrectomy.
Postoperative pathological complete response, defined as Becker tumor regression grade 1a or Ryan tumor regression grade 0, or major pathological response, defined as Becker tumor regression grade 1b or Ryan tumor regression grade 1 with 10 percent or less residual viable tumor.
Postoperative pathological assessment showing neither pathological complete response nor major pathological response, including more than 10 percent residual viable tumor or Becker tumor regression grade 2 to 3.
Distant metastatic disease identified intraoperatively or postoperatively.
Another malignant tumor within the previous 5 years.
Severe postoperative complications preventing any postoperative antitumor therapy.
Adults treated at The First Affiliated Hospital of Nanjing Medical University (Jiangsu Province Hospital) with histologically confirmed gastric or gastroesophageal junction adenocarcinoma who have completed neoadjuvant therapy, undergone R0 gastrectomy, and achieved pathological complete response or major pathological response.
Cohort
Prospective
Tumor-Informed ctDNA-MRD Monitoring
Diagnostic testPatient-specific somatic variants identified from tumor tissue are used to construct an individualized panel for ultra-deep sequencing of plasma cell-free DNA at prespecified perioperative and follow-up time points. Results are used for observational correlation and do not guide treatment changes.
Clinician-Selected Standard-of-Care Postoperative Treatment
Other interventionPostoperative treatment is selected by treating clinicians according to guidelines and individual clinical factors. The study does not assign, randomize, or modify treatment.
Three-Year Disease-Free Survival Rate
Disease-free survival is defined as the time from R0 gastrectomy to the first documented tumor recurrence or death from any cause, whichever occurs first. Participants without an event will be censored at the last disease assessment. The 3-year disease-free survival rate will be estimated using the Kaplan-Meier method.
Three-Year Overall Survival Rate
Overall survival is defined as the time from R0 gastrectomy to death from any cause. Participants alive at the last follow-up will be censored on that date. The 3-year overall survival rate will be estimated using the Kaplan-Meier method.
Lead Time From ctDNA-MRD Detection to Radiographic Recurrence
Among participants with recurrence, lead time will be calculated as the interval in days between the first postoperative ctDNA-MRD-positive result and the first radiographically documented recurrence. Positive values indicate that ctDNA-MRD detection preceded radiographic recurrence.
Sensitivity and Specificity of ctDNA-MRD for Postoperative Recurrence
Sensitivity and specificity of postoperative ctDNA-MRD status for detecting recurrence will be estimated using radiographic or clinically confirmed recurrence during follow-up as the reference standard.
Three-Year Disease-Free Survival by Postoperative Adjuvant Treatment Strategy
Among postoperative ctDNA-MRD-negative participants with pathological complete response or major pathological response, disease-free survival will be compared across clinician-selected standard-of-care postoperative adjuvant treatment strategies. Treatment is not assigned by the study. Analyses will account for measured baseline confounding using propensity score methods and multivariable models.
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