• Aged 18 to 80 years, regardless of gender.

‣ Histologically confirmed gastric cancer or gastroesophageal junction (GEJ) cancer that has received neoadjuvant therapy, with pathology confirming it is predominantly adenocarcinoma. For GEJ cancer, only Siewert Type III and Siewert Type II cases that do not require combined thoracotomy are eligible.

⁃ Tumor stage confirmed as cStage IV （ para-aortic lymph node enlargement without other distant metastatic factors）, suitable for curative R0 resection, as determined by an evaluation by a gastrointestinal surgeon and a radiologic technician prior to enrollment. The patient consented to conversion therapy followed by radical surgical resection, with no surgical contraindications confirmed by the attending surgeon.

⁃ No. 16 lymph nodes ≥10 mm

⁃ Subject must be previously untreated with systemic treatment; Subject that received neoadjuvant chemotherapy with recurrence \>6 months from completion of therapy are permitted;

⁃ Expected survival of ≥6 months.

⁃ Measurable tumor lesions as defined by RECIST v1.1 criteria (see Attachment 1).

⁃ Preoperative ECOG performance status score (see Attachment 2) of 0 or 1.

⁃ Good cardiac function, capable of undergoing a curative resection. If there are clinical indications, patients with underlying ischemic, valvular heart disease, or other serious heart conditions should undergo preoperative assessment by a cardiologist.

⁃ Normal major organ function, with the following laboratory criteria:

⁃ Absolute neutrophil count (ANC) ≥ 1.2 x 10\^9/L in the absence of granulocyte colony-stimulating factor use within the past 14 days.

⁃ Platelet count ≥ 100 x 10\^9/L in the absence of blood transfusion within the past 14 days.

⁃ Hemoglobin \> 8 g/dL in the absence of blood transfusion or erythropoietin use within the past 14 days.

⁃ Total bilirubin ≤ 1.5 × the upper limit of normal (ULN); if total bilirubin \> 1.5 × ULN but direct bilirubin ≤ ULN, inclusion is permitted.

⁃ Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.5 × ULN.

⁃ Serum creatinine ≤ 1.5 × ULN and creatinine clearance (calculated by the Cockcroft-Gault formula) ≥ 60 mL/min.

⁃ Coagulation function defined by international normalized ratio (INR) or prothrombin time (PT) ≤ 1.5 × ULN.

⁃ Normal thyroid function, defined by thyroid-stimulating hormone (TSH) within the normal range. If baseline TSH is outside the normal range, patients with normal total T3 (or FT3) and FT4 levels may still be eligible.

⁃ Normal range for myocardial enzyme profile (patients with isolated laboratory abnormalities deemed clinically insignificant by the investigator may still be included).

⁃ Thyroid function tests (TSH, FT3/FT4) within normal limits or with minor clinically insignificant abnormalities.

⁃ Weight ≥ 40 kg (inclusive) or BMI \> 18.5.

⁃ The participant has read, understood, and signed the informed consent form.