Aldesleukin With Nivolumab and Standard Chemotherapy for Treatment of Gastric Cancer With Peritoneal Metastasis

This trial is testing whether adding a drug called aldesleukin (a type of immune-boosting protein) to the standard immunotherapy and chemotherapy regimen (nivolumab + FOLFOX) can help treat stomach or gastroesophageal junction cancer that has spread to the lining of the abdomen (peritoneal metastasis). **You may be eligible if:** - You are 18 or older - You have confirmed adenocarcinoma (a type of cancer) of the stomach or where the stomach meets the esophagus - Your cancer has spread only to the lining of the abdomen (not to other organs like liver or lungs) - You are currently receiving or about to start FOLFOX chemotherapy plus nivolumab - You are in good enough health to participate (ECOG score 0–2) - You are willing to provide blood and tissue samples for research **You may NOT be eligible if:** - Your cancer has spread to organs other than the peritoneum (lining of the abdomen) - You are not on or not planning to start the required chemotherapy regimen - Your blood counts or organ function are below required levels Talk to your doctor to see if this trial is right for you.