A Study of the Drug I131-Omburtamab in People With Desmoplastic Small Round Cell Tumors and Other Solid Tumors in the Peritoneum

Inclusion Criteria: * Have the diagnosis of DSRCT confirmed at MSKCC * Age \>1 year and able to cooperate with radiation safety restrictions during therapy period. * Prior to intraperitoneal catheter placement * At least 1 weeks must have elapsed since prior chemotherapy * At least 2 weeks must have elapsed since biologic therapy * Toxicities of prior therapy must have resolved to grade 1 or less or to the patient's baseline At the completion of surgery, patients must fulfill all of the additional following criteria: * Have no definitive radiological evidence of disease active in liver or outside the abdomen/pelvic OR have had GTR of this disease at the time of catheter placement Exclusion Criteria: * Prior progression of disease * Prior hypothermic intraperitoneal chemotherapy (HIPEC) * Cardiac, pulmonary, and neurologic toxicities are greater grade 1 per NCI CTCAE version 5 * Renal, gastrointestinal, and hepatic, toxicities are greater than grade 2 (per NCI CTCAE version 5) * History of allergy to mouse proteins * Patients with grade 4 hypersensitivity reaction to radiolabeled iodine