Surgical Conversion of Candonilimab (AK104) Plus Paclitaxel, S-1 and Apatinib for Unresectable Advanced G/GEJ Cancer

Inclusion Criteria: Males or females aged ≥ 18 to ≤ 75 years at the time of signing informed consent. Clinically diagnosed unresectable stage IV gastric (G) or gastroesophageal junction (GEJ) adenocarcinoma by CT/MRI/Positron Emission Tomography (PET) -CT. Not received prior systemic therapy for stage IV G/GEJ adenocarcinoma At least one measurable tumor lesion per RECIST v1.1; Major organ functions are adequate; Expected survival is ≥ 3 months; Eastern Cooperative Oncology Group performance status (ECOG PS) 0-1; Exclusion Criteria: Human Epidermal GrowthFactor Receptor 2 (HER2)-positive G/GEJ adenocarcinoma; Previously received immune checkpoint inhibitors, including but not limited to programmed death 1 (PD-1) inhibitors and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) inhibitors; Central nervous system, lung, or bone metastases; Known history of active or autoimmune disease; Known history of other malignancies; Known history of severe cardiovascular and cerebrovascular diseases; Known history of gastrointestinal bleeding within the past 3 months or significant tendency to gastrointestinal bleeding; Active infection or fever of unknown origin; Known history of pulmonary fibrosis, interstitial pneumonia, pneumoconiosis, radiation pneumonitis, drug-related pneumonia, and severe impairment of lung function; Known history of immunodeficiency, positive HIV antibody (HIVAb) test, or other acquired or congenital immunodeficiency disorder, or active hepatitis; Known history of mental disorder or psychoactive substance abuse; Hypersensitivity to the drugs of this regimen;