Safety and Efficacy of Pembrolizumab in Combination With FLOT About Gastroesophageal Junction Cancer:

Inclusion Criteria:

* 1\) aged from 18 to 75 years old, including 18 and 80 years old;

  2\) histologically or cytologically confirmed locally advanced unresectable or metastatic gastric or GEJ adenocarcinoma;

  3\) ECOG PS score 0 or 1;

  4\) Known PD-L1 expression (assessed centrally using PD-L1 HC22C3)

  5\) no previous treatment

  6\) HER2-negative status

  7\) normal hematological parameters: white blood cell count ≥4×109/L; Absolute neutrophil count ≥1.5×109/L; Platelet count ≥100×109/L; Blood red protein g/L;

  8\) basically normal renal function: serum creatinine ≤1.5×ULN or creatinine clearance (CrCl)\> 60 mL/min(using Cockcroft-Gault formula):

Female CrCl=(140-age)× weight (kg)× 0.85 / (72×Scr mg/dl)

Male CrCl=(140-age)× weight (kg)× 1.00 / (72×Scr mg/dl)

Liver function was basically normal: serum total bilirubin ≤1.5×ULN; Aspartate aminotransferase (AST) ≤2.5×ULN; Alanine aminotransferase (ALT) ≤2.5×ULN.

Female patients must have a negative urine pregnancy test before the start of the study (not applicable to patients with bilateral oophorectomy and/or hysterectomy or postmenopausal patients)

9\) Provide written informed consent. Written informed consent was obtained.

Exclusion Criteria:

* 1\) receiving anti-tumor therapy before enrollment, including but not limited to PD-1 inhibitors, CTLA-4 antibodies, EGFR monoclonal antibodies, EGFR-Tkis, and anti-angiogenic drugs;

  2\) A history of autoimmune disease, including but not limited to: myasthenia gravis, myositis, autoimmune hepatitis, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, antiphospholipid syndrome-related vascular thrombosis, Wegener's granulomatosis, Sjogren's syndrome, Guillain-Barre syndrome, multiple sclerosis, vasculitis, or glomerulonephritis. (Note: Patients with vitiligo, type I diabetes, or residual hypothyroidism due to autoimmune conditions (e.g., after Hashimoto's syndrome) requiring only hormone-replacement therapy, psoriasis requiring no systemic therapy, or if recurrence was not expected in the absence of an external trigger were allowed.) ;

  3\) participated in other interventional clinical trials within 30 days before screening;

  4\) Patients with a history of other malignant tumors (except cured basal cell carcinoma)

  5\) with severe uncontrolled comorbidities (e.g., heart failure, diabetes mellitus, hypertension, liver failure, renal failure, thyroid disease, mental illness, etc.);

  6\) known HIV infection or active viral hepatitis or tuberculosis;

  7\) have a major surgical procedure or planned surgery within 30 days before the first dose of the trial drug;

  8\) patients who are allergic to the drugs used in this regimen or their components;

  9\) pregnant (confirmed by blood or urine HCG testing) or lactating women, or childbearing age subjects unwilling or unable to use effective contraception (for both male and female subjects) until at least 6 months after the last trial treatment;

  10\) The investigator considers that it is not appropriate to participate in the study;

  11\) unwilling to participate in the study or unable to sign an informed consent form