RecruitingPhase 1Biological interventionAldesleukin With Nivolumab and Standard Chemotherapy for Treatment of Gastric Cancer With Peritoneal MetastasisThis phase Ib trial test effects of aldesleukin in combination with nivolumab and standard chemotherapy in treating patients with gastric cancer that has spread to the tissue lining of the abdomen (peritoneal metastasis). Aldesleukin is similar to a protein that naturally exists in the body that stimulates the immune system to fight infections. Immunotherapy with monoclonal antibodies, such as nivolumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Chemotherapy drugs, such as leucovorin calcium, fluorouracil, and oxaliplatin, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Giving aldesleukin in combination with nivolumab and standard chemotherapy may work better in treating patients with gastric cancer with peritoneal metastasis.