HSV G207 With a Single Radiation Dose in Children With Recurrent High-Grade Glioma

Treatment Inclusion Criteria: Patients meeting the following inclusion criteria will be eligible for the study: * Patients must have a histologically confirmed diagnosis of high-grade glioma regardless of molecular characterization that is recurrent or progressive. All tumors must have histologic verification at either the time of diagnosis or recurrence. * Patients are only eligible after their first progression following prior surgery and radiotherapy * Supratentorial lesion must be ≥ 1.0 cm in longest dimension and surgically accessible as determined by contrast-enhanced MRI * For patients with tumors \> 4.0 cm without an adjacent cavity, the neurosurgeon must be confident that the tumor can be debulked to ≤ 4.0 cm for eligibility. * Multifocal disease on the ipsilateral side is eligible if at least one catheter can be placed in all multifocal areas * Tumor size will be determined using the maximal 2-dimensional cross-sectional tumor measurements, transverse x width, using either T1 images or T2/FLAIR images for non-enhancing tumors. * Patient must be ≥ 3 at initial diagnosis but \< 22 years of age at the time of enrollment on this study. * Prior therapy: Patients must have received prior surgery and radiotherapy and recovered from the acute treatment related toxicities (defined as ≤ Grade 1 if not defined in eligibility criteria; excludes alopecia) prior to enrollment. * Chemotherapy: Patients must have received their last dose of known myelosuppressive anticancer thera…