This study is to evaluate the efficacy and safety of chemotherapy combined with or without immunotherapy as postoperative adjuvant regimens in patients with resectable gastric cancer/adenocarcinoma of the esophagogastric junction after radical surgery

Inclusion Criteria:

1. Age ≥ 18 years old, gender not restricted;
2. Subjects diagnosed with gastric cancer (GC) or gastroesophageal junction cancer (GEJC) through imaging and other examinations, and with histopathological diagnosis of adenocarcinoma;
3. HER2 overexpression or amplification results are negative;
4. After radical surgery treatment, the investigator assesses that further adjuvant treatment is necessary, and the adjuvant treatment plan must be the one specified in this protocol.

Exclusion Criteria:

1. Gastric cancer that is known to be squamous cell carcinoma, undifferentiated carcinoma, or of other tissue types, or gastric cancer that is adenocarcinoma mixed with other tissue types;
2. Within 3 months before adjuvant therapy, there was a significant clinically significant bleeding symptom or a clear bleeding tendency;
3. Within 6 months before adjuvant therapy, had suffered from intestinal obstruction and/or had clinical signs or symptoms of digestive tract obstruction, including incomplete obstruction related to the original disease or requiring routine parenteral hydration, parenteral nutrition, or tube feeding;
4. Within 5 years before starting adjuvant therapy, was diagnosed with a malignant tumor (excluding malignant tumors with low metastasis and mortality risks, such as: skin basal cell carcinoma or cervical carcinoma in situ that has been adequately treated);
5. Within 30 days before starting adjuvant therapy, had participated in other clinical studies and used study drugs containing active ingredients;