This study is to determine the performance of non-invasive new multi-target biomarkers in the early detection and post-operative monitoring of gastric cancer.

This study aims to develop and validate a new non-invasive detection method for early detection and postoperative monitoring of gastric cancer in the blood. Sensitivity, specificity, accuracy, ROC curve area, positive predictive value, and negative predictive value of the new biomarkers in the diagnosis of gastric cancer will be compared with that of tumor biomarkers CA19-9, CEA, and CA72-4. Blood will also be collected at various time points post-operatively. The investigators will determine whether these new biomarkers can be used as prognostic biomarkers to predict tumor recurrence and metastasis. The investigators will also determine whether these new biomarkers detect tumor recurrence and metastasis earlier than methods currently used in the clinic such as imaging and tumor biomarkers CA19-9, CEA, and CA72-4.

This study is a prospective and multi-center study.

Inclusion Criteria:

1. Subject age over 18.
2. Subject has stomach discomfort, and seek medical attention at the Gastric Surgery Department of our center.
3. Subject has or will have gastroscopy and/or pathological examination results at this center.
4. Subject must be able to fully understand the informed consent form and be able to personally sign it.

Exclusion Criteria:

1. Subject has serious heart, liver, kidney dysfunction, or mental illness.
2. Subject diagnosed previously with any kind of malignant tumor.
3. Subject is known to be infected with HIV or other related diseases (considering interference from the use of immune drugs).
4. Subject is receiving targeted drugs, immunosuppressants, immunomodulators, and biological therapies.
5. Researchers believe that subject is not suitable for enrollment.
6. Subject can not supply sufficient sample to complete this experiment.

Subjects age over 18, regardless of gender or region, and those who meet the inclusion criteria for this clinical trial, are eligible to enroll at the designated clinical sites. More than 1197subjects are targeted to enroll.