Stratum 1: This is a phase 2 single-arm open-label study that will define event-free survival (EFS) and overall survival (OS) following therapy with irinotecan, temozolomide, bevacizumab, and compartmental (intraOmmaya) radioimmunotherapy (cRIT) 131I-omburtamab in patients with recurrent medulloblastoma. Patients with recurrent medulloblastoma will undergo surgery if feasible prior to study entry, followed by Induction Chemotherapy with irinotecan, temozolomide, and bevacizumab on study as per the Children's Oncology Group (COG) trial ACNS0821. Following 2 or 4 courses of chemotherapy and if radiographic disease status is stable or improved, patients may continue to Radioimmunotherapy to receive 2 therapeutic doses (50 mCi each) of cRIT 131I-omburtamab. Following Radioimmunotherapy, patients may resume to Maintenance Chemotherapy with irinotecan, temozolomide, and bevacizumab for up to 12 total courses of chemotherapy or until disease progression, whichever occurs sooner. The primary comparison for this study will be the medulloblastoma cohort treated on ACNS0821 on the irinotecan + temozolomide + bevacizumab arm (N=52).~Stratum 2: This is a feasibility cohort. The primary objective is to assess feasibility of incorporating cRIT 131I-omburtamab for patients with recurrent ependymoma and to assess dosimetry. Patients must have progressed after initial surgery, radiation therapy, or other therapies. Patients will undergo surgery (if feasible) prior to study entry with the goal of achieving stable or better disease. Tumors (archived or new) will be tested for B7H3 prior to enrollment. If positive, patients will enroll on Stratum 2 and receive one dosimetry dose (2 mCi) of cRIT 131I-omburtamab with nuclear medicine scintigraphy (typically using 3 whole-body planar gamma camera imaging and at least 1 head SPECT scan or SPECT/CT) using SPECT during the Dosimetry Course (14 days in length). Following the Dosimetry Course and within 2 weeks of the dosimetry dose, patients may continue to Radioimmunotherapy to receive 2 therapeutic doses (50 mCi each) of cRIT 131I-omburtamab.
A Phase 2 study investigating the addition of cRIT 131I-omburtamab to irinotecan, temozolomide, and bevacizumab for patients with recurrent medulloblastoma. A feasibility cohort is included to assess the feasibility of incorporating cRIT 131I-omburtamab for patients with recurrent ependymoma.~Direct intraventricular delivery of radiolabeled tumor-specific antibodies may aid in both the detection and treatment of recurrent disease for these highly specific pediatric patients with recurrent tumors.