Early gastric cancer（AGC）has no effective characteristic symptoms and signs according to clinical statistics. Neoadjuvant chemotherapy (NAC) significantly reduces the size of AGC tumors so that it has become the recommended treatment for AGC in major guidelines. However, Some patients miss the best time for surgical treatment and may have irreversible chemotherapy side effects due to NAC lacks the guidance of new indicators for precise treatment such as molecular biomarkers. Tumor organoids are highly consistent with the clinical drug sensitivities of patients which could be used as clinical treatment prediction models thus providing guidance for individualized medicine. Therefore, the project is the first to carry out the prospective study by screening the potential benefit populations of NAC based on tumor organoids drug susceptibility experiment. The following hypothesis are put forward：the potential benefit population of NAC screened by tumor organoid drugs susceptibility technology will have better clinical efficacy, better treatment tolerance and higher adverse reaction rate.

Inclusion Criteria:

1. Age: 18-75 years old;

2. Qualitative diagnosis: gastroscopic biopsy confirmed adenocarcinoma;

3. Localization diagnosis: the tumor is located in the stomach or gastroesophageal junction;

4. The clinical staging is stage III:

   A. Assess tumor stage: T3-4N1-2; B. Excluding distant organ metastasis (M0);

5. Physical condition (ECOG) score ≤ 1 point;

6. Those with effective preoperative neoadjuvant therapy and successful surgery agreed to receive 5 cycles of standard SOX chemotherapy after surgery;

7. Sign the informed consent form and be willing to participate in this project.

Exclusion Criteria:

1. Simultaneous or metachronous multiple primary malignant tumors;

2. Preoperative imaging examination results showed that there was distant metastasis;

3. Preoperative imaging findings:

   A. The tumor involving surrounding organs requires combined organ resection; B. Distant organ metastases; C. Those who cannot perform R0 resection;

4. Past history of malignant tumor;

5. Abnormal heart, lung, liver, kidney, hematopoietic function and bone marrow reserve function, unable to tolerate surgical treatment and chemotherapy;

6. Mental illness or other serious cardiovascular disease;

7. Pregnant or lactating women.

Patients with AGC who need NAC before radical surgery.