Study: NCT05161572

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Oxaliplatin
Description: The SOX regimen consists of S-1 and oxaliplatin and is repeated every three weeks. Oxaliplatin will be administered intravenously at 130 mg/m2 on day 1.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Oxaliplatin
Description: The SOX regimen consists of S-1 and oxaliplatin and is repeated every three weeks. Oxaliplatin will be administered intravenously at 130 mg/m2 on day 1.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Tegafur-Gimeracil-Oteracil
Description: The SOX regimen consists of S-1 and oxaliplatin and is repeated every three weeks. S-1 is administered orally at 40-60 mg twice a day for 14 consecutive days. Then, the patients will have a one-week rest period. The dose of S-1 is according to the body-surface area (BSA): patients with a BSA of less than 1.25 m2 receive 80 mg daily; those with a BSA of 1.25 m2 or more but less than 1.5 m2 receive 100 mg daily; and those with a BSA of 1.5 m2 or more receive 120 mg daily.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Tegafur-Gimeracil-Oteracil
Description: The SOX regimen consists of S-1 and oxaliplatin and is repeated every three weeks. S-1 is administered orally at 40-60 mg twice a day for 14 consecutive days. Then, the patients will have a one-week rest period. The dose of S-1 is according to the body-surface area (BSA): patients with a BSA of less than 1.25 m2 receive 80 mg daily; those with a BSA of 1.25 m2 or more but less than 1.5 m2 receive 100 mg daily; and those with a BSA of 1.5 m2 or more receive 120 mg daily.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Sintilimab
Description: The immunotherapy includes perioperative treatment and postoperative maintenance treatment. The PD-1 mAb used will be sintilimab, and the dose is 200 mg intravenously every three weeks. Regardless of which arm, the courses of immunotherapy that will be received by the enrolled patients are the same: 3 times preoperatively, 3 times postoperatively, and then maintained until one year after surgery.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Sintilimab
Description: The immunotherapy includes perioperative treatment and postoperative maintenance treatment. The PD-1 mAb used will be sintilimab, and the dose is 200 mg intravenously every three weeks. Regardless of which arm, the courses of immunotherapy that will be received by the enrolled patients are the same: 3 times preoperatively, 3 times postoperatively, and then maintained until one year after surgery.

Intervention type: RADIATION
Group type: EXPERIMENTAL
Intervention: Concurrent chemoradiation
Description: The radiotherapy (RT) consists of 45 Gy delivered in 25 fractions every five days per week for five weeks. The dose of concurrent ChT is 60 mg/m2 S-1 orally, oral tablets twice daily, days 1-5 of each week.

Intervention type: PROCEDURE
Group type: EXPERIMENTAL
Intervention: D2/R0 gastrectomy
Description: Gastrectomy with standard D2 lymphadenectomy is recommended. The type of gastrectomy performed depends on the location and extent of the primary lesion. For GEJ or upper third tumors, a 3 cm esophageal margin is recommended, and a total gastrectomy or esophagogastrectomy is performed. For middle third tumors, the gastric margin is recommended to be more than 5 cm, and a total gastrectomy is performed. For lower third tumors, a 2 cm duodenal margin is recommended, and a subtotal or total gastrectomy is performed. Billroth I or Roux-en-Y gastrojejunostomy is performed for distal gastrectomy patients. Roux-en-Y esophagojejunostomy is performed for patients receiving total gastrectomy.

Intervention type: PROCEDURE
Group type: EXPERIMENTAL
Intervention: D2/R0 gastrectomy
Description: Gastrectomy with standard D2 lymphadenectomy is recommended. The type of gastrectomy performed depends on the location and extent of the primary lesion. For GEJ or upper third tumors, a 3 cm esophageal margin is recommended, and a total gastrectomy or esophagogastrectomy is performed. For middle third tumors, the gastric margin is recommended to be more than 5 cm, and a total gastrectomy is performed. For lower third tumors, a 2 cm duodenal margin is recommended, and a subtotal or total gastrectomy is performed. Billroth I or Roux-en-Y gastrojejunostomy is performed for distal gastrectomy patients. Roux-en-Y esophagojejunostomy is performed for patients receiving total gastrectomy.