Adjuvant Serplulimab and Trastuzuma and Chemotherapy in Her-2+ Gastric Cancer

This study is testing whether adding serplulimab (an immunotherapy drug) to standard trastuzumab (targeted HER2 therapy) plus chemotherapy after surgery improves outcomes for patients with HER2-positive gastric (stomach) cancer. **You may be eligible if...** - You are 20–80 years old - You have been diagnosed with stage II or III gastric (stomach) cancer that is HER2-positive - You have had surgery removing the tumor with clear margins (R0 resection) and full lymph node removal (D2) - You are in good physical health (ECOG score 0–1) and expected to survive at least 6 months - Your blood counts, liver, and kidney function are within acceptable range **You may NOT be eligible if...** - Your cancer is stage I or stage IV - You have had multiple different primary cancers - You have serious heart or other organ disease that prevents treatment Talk to your doctor to see if this trial is right for you.