This project intends to compare the clinical effects and side effects of three kinds of treatment methods in the treatment of unresectable gastric cancer by intra-arterial catheter infusion chemotherapy combined with sodium bicarbonate and systemic chemotherapy. It is clear that intra-arterial catheter infusion chemotherapy combined with sodium bicarbonate is not suitable for the treatment of unresectable gastric cancer. The clinical practice value of resection of gastric cancer can provide high quality evidence-based medical basis for the treatment guidelines of advanced gastric cancer, and explore a new clinical technology with exact curative effect and higher safety.

Inclusion Criteria:

1. Patients aged 18 to 75 years;
2. Ultrasound gastroscopy or imaging (CT) can diagnose potentially unresectable gastric cancer (T4a-bN2-3M0) with indications of neoadjuvant chemotherapy or transformation therapy;
3. Pathological diagnosis of gastric cancer;
4. No contraindication of chemotherapy;
5. Patients who did not undergo chemotherapy or were diagnosed for the first time.

Exclusion Criteria:

1. Those who fail to comply with the requirements of the trial, obviously violate this regimen, or change to other regimens in the course of treatment;
2. The life expectancy of patients with extensive systemic metastasis is less than 3 months;
3. Leukocyte count is less than 2*109/L and platelet count is less than 75*10^9/L;
4. Severe heart, liver and kidney diseases, unable to tolerate chemotherapy;
5. Patients without gastric cancer complications such as massive gastrointestinal bleeding and perforation need to be treated in emergency department;
6. Patients with distant metastasis (excluding group 16 lymph node metastasis);
7. Patients with other tumors, with a history of malignant tumors (excluding early primary cancers);
8. The patient himself asked to withdraw from the trial;
9. Researchers believe that patients are not suitable for this study.