Lymph node positive patients after D2 radical surgery for gastric cancer, who started to be treated at Yixing people's Hospital in April 2021, were selected and enrolled into the study group according to the patients' wishes: immune (tirelizumab) combined with chemotherapy (XELOX regimen) or control group: chemotherapy alone (XELOX regimen). Each enrolled patient signed an informed consent form approved by the ethics committee, signed, and dated. Efficacy and adverse effects were assessed in both groups.

Inclusion criteria：(1) With a good bone marrow reserve, e. g. : leukocytes ≥ 4 × 109 / L, neutrophils ≥ 1.5 × 109 / L, platelets ≥ 100 × 109 / L and hemoglobin ≥ 90 g / L.(2) Cardiopulmonary function was unremarkable.(3) There were no abnormalities in liver and kidney function. For example: creatinine ≤ 1.5 × ULN or a calculated serum creatinine clearance ≥ 50 ml / min (calculated according to the Cockcroft Gault formula), albumin ≥ 30 g / L, and total bilirubin ≤ 1.5 × ULN, alanineaminotransferase (ALT) / aspartate aminotransferase (AST) ≤ 2 × ULN.(4) International normalized ratio / activated partial thromboplastin time ≤ 1.5 × ULN.(5) Age older than 18 years, karonfsky performance status (KPS) score ≥ 80, and premedication patients' bone marrow status, liver and kidney function, and cardiopulmonary function had little impact on prognosis.

Exclusion criteria: Had a previous history of immunodeficiency, or had other acquired, congenital immunodeficiency diseases, or a history of organ transplantation; Preexisting thyroid dysfunction and, with medical therapy, thyroid function still cannot be maintained within the normal range; Women who were pregnant or lactating; Those with a history of substance abuse who are unable to abstain or who have a mental disorder.