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

The purpose of this study is to test any good and bad effects of the study drug 131I-omburtamab. 131I-omburtamab could prevent the cancer from returning, or delay the cancer from getting worse, but it could also cause side effects. Researchers hope to learn more about how 131I-omburtamab works in the body, and how effective it is in treating cancer. 131I-Omburtamab is not approved by the FDA to treat DSRCT or other cancers of 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