Lenvatinib Plus Tislelizumab and CapeOX as First-Line Treatment for Advanced GC/GEJC With Positive PD-L1 and Low TMEscore

Inclusion Criteria: 1. Patients voluntarily participated in the study, signed the informed consent, and had good compliance; 2. Age over 18 (including 18 years old), gender is not limited; 3. Histologically and/or cytologically confirmed advanced gastric cancer or gastroesophageal junction adenocarcinoma (stage IV); 4. Tumor with PD-L1 positive and low tumor microenvironment score (TMEscore) 5. Have not received systemic antitumor therapy before; Or have previously received adjuvant or neoadjuvant therapy (chemotherapy/radiotherapy) for the purpose of cure, and the time of tumor recurrence \> 6 months since the last treatment 6. ECOG performance status of 0-2 points; 7. Expected survival ≥12 weeks; 8. Blood test (without blood transfusion within 14 days) 1) Neutrophil absolute value ≥1.5×10\^9/L, platelet ≥100×10\^9/L, hemoglobin ≥90g/L); 2) Liver function test (aspartate aminotransferase and glutamate aminotransferase ≤3×ULN, bilirubin ≤1.5×ULN; In case of liver metastasis, AST and ALT≤5×ULN); 3) Renal function (serum creatinine ≤1.5×ULN, or creatinine clearance (CCr)≥60ml/min); 9. Men and women of childbearing age must use effective contraceptive methods. Exclusion Criteria: 1. Previously received therapy that targets T cell co-stimulation or checkpoint pathways ,such as anti-PD-1 antibodies, anti-PD-L1 antibodies, anti-CTLA-4 antibodies, etc.; 2. Previously received anti-vascular small-molecule targeted drug therapy, such as fuquinitinib, regofenib, etc.; 3. Received major surgery within 4 weeks prior to the first drug administration; radiotherapy, radiofrequency ablation and other investigational drugs for tumors within 2 weeks; 4. Received live vaccine within 4 weeks prior to the first drug administration (except inactivated viral vaccine for seasonal influenza); 5. A history of severe intolerance to drugs involved in the study (i.e., grade 4 toxicity of one of these drugs; Class 3-4 toxicity of other co-administered drugs is not excluded); 6. Known allergy to the study drug or any of its excipients; 7. HER2 positive gastric cancer or gastroesophageal junction adenocarcinoma; 8. The patient had other malignancies within the previous 5 years or at the same time (except cured basal cell carcinoma, stage I squamous cell carcinoma, in situ carcinoma, intramucosal carcinoma, and superficial bladder cancer); 9. Known brain or meningeal metastases; 10. Patients who are preparing for or have previously received an organ or bone marrow transplant; 11. A history of human immunodeficiency virus (HIV) infection; 12. A history of psychotropic substance abuse or drug use; 13. Condition that may interfere with the detection and management of suspected drug-related pulmonary toxicity, such as interstitial pneumonia, pneumoconiosis, radiation pneumonia, drug-related pneumonia, or severe impairment of lung function; 14. Known active or suspected autoimmune disease (except for patients with stable disease at enrollment who do not require systemic immunosuppressive therapy); 15. Patients who required systemic corticosteroids (\> 10 mg/ day efficacy dose of prednisone) or other immunosuppressive agents within 2 weeks prior to initial administration or during the study period. However, adrenal hormone replacement therapy with topical or inhaled steroids, or a therapeutic dose of prednisone ≤ 10mg/ day in the absence of active autoimmune disease was permitted; 16. Any active infection that requires systematic anti-infective treatment occurs within 2 weeks prior to the first dose (expect prophylactic antibiotic therapy, such as for urinary tract infections or chronic obstructive pulmonary disease); 17. Active heart disease, including myocardial infarction, severe/unstable angina in the 6 months prior to treatment. Echocardiography showed that the left ventricular ejection fraction was less than 50%, indicating poor arrhythmia control. 18. Obvious clinical bleeding symptoms or obvious bleeding tendency and hemoptysis within 3 months prior to treatment. Or treatment of venous/venous thrombosis events within the preceding 6 months, such as cerebrovascular accidents (including transient ischemic attack, cerebral hemorrhage, cerebral infarction), deep vein thrombosis and pulmonary embolism; Long-term anticoagulant therapy with warfarin or heparin, or long-term antiplatelet therapy (aspirin ≥300 mg/day or clopidogrel ≥75 mg/day) is required; 19. Any other disease, a clinically significant metabolic abnormality, abnormal physical examination or abnormal laboratory examination, for which, in the investigator's judgment, there is reason to suspect that the patient has a disease or condition unsuitable for the use of the investigational agent; 20. Anything that, in the investigator's opinion, could put subjects receiving the study drug at risk, interfere with the study drug, subject safety assessment, or interpretation of the results; 21. Pregnant or lactating women or women who may become pregnant.