Tislelizumab Combined With Apatinib and Oxaliplatin Plus S1 Vs Oxaliplatin Plus S1 as Neoadjuvant Therapy for Borrmann IV、Large Borrmann III Type and Bulky N Positive Advanced Gastric Cancer

This study tests whether adding tislelizumab (an immunotherapy) and apatinib (a targeted blood vessel-blocking drug) to standard chemotherapy (oxaliplatin plus S1) before surgery improves outcomes for patients with locally advanced gastric (stomach) cancer that is particularly large or has spread to nearby lymph nodes. **You may be eligible if...** - You are 18–70 years old with locally advanced gastric adenocarcinoma confirmed by biopsy - Your cancer is classified as large Borrmann III, Borrmann IV, or bulky N-positive (meaning significant lymph node involvement) - You have not previously received surgery, chemotherapy, radiation, or immunotherapy for this cancer - Your expected survival is more than 6 months **You may NOT be eligible if...** - You have cancer that has spread to the peritoneum (lining of the abdomen) or distant organs - You have significant heart, liver, or kidney problems - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.