Tislelizumab in Combination With Pre-operative CRT Versus SOC for Locally Advanced G/GEJ Adenocarcinoma

This study compares two approaches to treating locally advanced stomach or gastroesophageal junction cancer (cancer where the stomach meets the food pipe): the standard chemotherapy approach before surgery versus adding an immunotherapy drug (tislelizumab) combined with radiation before surgery. **You may be eligible if...** - You have locally advanced stomach or gastroesophageal junction cancer (adenocarcinoma) that has not spread to distant organs - You have not received any prior treatment for this cancer - You are in good physical health (ECOG 0–1) - Your organ function (kidney, liver, blood) meets minimum requirements - You are willing to use contraception during the study **You may NOT be eligible if...** - You have another active cancer that required treatment in the past 5 years - You have received prior systemic treatment for this cancer - You have an active infection requiring treatment - You have had pneumonia requiring steroids - You are pregnant or breastfeeding - You have serious autoimmune disease Talk to your doctor to see if this trial is right for you.