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 therapyperiod.

• 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 thepatient'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 theabdomen/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 CTCAEversion 5

• Renal, gastrointestinal, and hepatic, toxicities are greater than grade 2 (per NCICTCAE version 5)

• History of allergy to mouse proteins

• Patients with grade 4 hypersensitivity reaction to radiolabeled iodine