NGS can not only detect tissue samples, but also blood samples. For some inoperable cancer patients, the acquisition of tissue samples is difficult and traumatic. It is of great significance for the diagnosis and treatment of these patients to determine MSI status by blood testing. In addition, the heterogeneity of malignant tumors is usually strong, blood testing can overcome the heterogeneity of tissue, and can dynamically monitor the patient's condition. 50 patients with gastric cancer, duodenal cancer and small intestinal cancer will be enrolled in the study. Among them, 30 patients with MSI-H and 20 patients with MSS confirmed by IHC/PCR.The investigators will use 520 gene panel for NGS sequencing of tissue and blood samples from selected patients to study the sensitivity and specificity of NGS in detecting Microsatellite State in blood.
To study the sensitivity and specificity of NGS in detecting Microsatellite State in blood and to evaluate its potential application in gastrointestinal cancer.