Neoadjuvant Immunotherapy Plus Chemotherapy in Borrmann Type 4 and Large Type 3 Gastric Cancer

This study tests whether combining immunotherapy with chemotherapy before surgery (called neoadjuvant treatment) is effective for people with a particularly aggressive form of stomach cancer — specifically a diffuse, leather-bottle type (Borrmann type 4) or a very large tumor (over 8 cm). **You may be eligible if...** - You are aged 18–70 and have been diagnosed with stomach cancer confirmed by biopsy - Your cancer is a diffuse/scirrhous type (Borrmann type 4) or a large type 3 tumor over 8 cm - Your cancer has not spread to the abdominal lining (peritoneum) - You are in good general health (able to carry out daily activities) - You have not had any prior cancer treatment **You may NOT be eligible if...** - You have had another cancer in the past 5 years - You have previously received chemotherapy, radiation, or immunotherapy - You are pregnant or breastfeeding - You cannot take medications by mouth Talk to your doctor to see if this trial is right for you.