Numerous studies have demonstrated that circulating tumor DNA (ctDNA)-based molecular residual disease (MRD) detection has significant clinical value in postoperative recurrence monitoring, adjuvant treatment decision-making, and early intervention. Our previous retrospective study, using fixed ctDNA-MRD, confirmed that postoperative ctDNA-MRD can predict recurrence risk. Therefore, we plan to conduct a further prospective, multicenter, observational study, utilizing a combination of personalized ctDNA-MRD and fixed MRD panels, to dynamically monitor gastric cancer patients who have received neoadjuvant therapy followed by curative resection. The study will systematically analyze the correlation between ctDNA-MRD status and tumor recurrence and metastasis, assess its sensitivity and specificity in recurrence prediction, and compare its early warning advantage over traditional imaging techniques in predicting recurrence.

China has the highest incidence and mortality rates of gastric cancer in the world, with approximately 70% of patients diagnosed at an advanced stage. Perioperative treatment combined with surgery is the recommended treatment approach for advanced gastric cancer. However, a considerable proportion of patients still experience recurrence and metastasis after surgery. Imaging studies are the standard method for monitoring postoperative recurrence and metastasis, but they can only detect recurrence once the metastatic lesions have grown to a certain size. In contrast, ctDNA-MRD testing can detect residual tumor molecular signals in the blood, providing early signs of recurrence and allowing for timely intervention while the tumor is still in its "incipient stage." Previous clinical data have shown that MRD testing can identify recurrent and metastatic patients months earlier than traditional imaging methods, with the median lead time varying by cancer type: 9.5 months for breast cancer, 8.7 months for colon cancer, 5.2 months for lung cancer, and 2.8 months for bladder cancer.

Therefore, we plan to conduct a further prospective, multicenter, observational study, utilizing a combination of personalized ctDNA-MRD and fixed MRD panels, to dynamically monitor gastric cancer patients who have received neoadjuvant therapy followed by curative resection. The study will systematically analyze the correlation between ctDNA-MRD status and tumor recurrence and metastasis, assess its sensitivity and specificity in recurrence prediction, and compare its early warning advantage over traditional imaging techniques in predicting recurrence. In addition, this project will focus on establishing and improving a dynamic MRD monitoring system, laying the foundation for future interventional clinical research.

Inclusion Criteria:

1. Patients have received neoadjuvant therapy and radical resection (R0).
2. Pathologically confirmed ypTNM stage II-III gastric or gastroesophageal junction adenocarcinoma.
3. Patients must be able to provide sufficient fresh tissue/biopsies or minimum 5-10 FFPE sections for NGS-WES analysis.
4. Patients must be able to follow the study visit schedule and be willing to cooperate with the study by providing blood samples at the indicated time point.

Exclusion Criteria:

1. Patients who could not receive enhanced CT, gastroscopy and other routine review after surgery.
2. Patients who could not perform WES or ctDNA-MRD detection for various reasons after surgery.
3. Other cases considered unsuitable for inclusion by researchers.

110 patients with gastric cancer undergoing preoperative drug therapy combined with R0 resection were enrolled.