Lutathera for Treatment of Recurrent or Progressive High-Grade CNS Tumors

All participants must meet the following inclusion and exclusion criteria. No exceptions will be given. Imaging studies to establish eligibility must be done within three weeks prior to enrollment. All other clinical evaluations to establish eligibility (except for \[68Ga\]Ga-DOTATATE PET) must be done within 7 days prior to enrollment. 1. Screening Criteria 1.1 Diagnosis Patient must have a diagnosis of primary high-grade CNS tumor (any histopathologic diagnosis that is WHO grade III-IV) or meningioma (any histologic grade) that is recurrent, progressive, or refractory. Note that patients with DIPG (based on radiographic/clinical diagnosis) who have undergone biopsy will be eligible with histologic diagnosis of grade II-IV infiltrating glioma. All tumors must have histologic verification either at the time of diagnosis or recurrence, except for patients meningioma who have not previously undergone biopsy or resection. Note: Refractory disease is defined as the presence of persistent abnormality on conventional MRI that is further distinguished by histology (biopsy or sample of lesion) or advanced imaging, OR as determined by the treating physician and discussed with the primary investigator prior to enrollment. 1.2 Prior Therapy Patients must have recurred/progressed following prior standard therapy for their tumor. Note: Patients with meningioma, atypical meningioma, or anaplastic meningioma must have received at least surgical resection or radiation. 1.3 Screening Consent Participant/legal guardian is willing to sign a screening consent for \[68Ga\]Ga-DOTATATE PET imaging. The screening consent is to be obtained according to institutional guidelines. Assent, when appropriate, will be obtained according to institutional guidelines. 2. Eligibility Criteria * Phase I Age Patient must be ≥ 4 and \<12 years of age at the time of enrollment. Disease Status: Patients who participate in the efficacy expansion cohort must have bi-dimensionally measurable disease, defined as at least one lesion that can be accurately measured in at least two dimensions Patients with measurable extraneural disease only are also eligible. * Phase II Age Patient must be 12 to \</=39 years at the time of enrollment. 3. Inclusion Criteria 3.1 Uptake on \[68Ga\]Ga-DOTATATE PET Patients must have uptake on DOTATATE PET/CT in at least one tumor lesion (corresponding to known disease) equivalent to a Krenning score ≥2 (confirmed by central radiology review). 3.2 Prior Therapy Patients must have recovered from the acute treatment related toxicities (defined as ≤ grade 1 if not defined in eligibility criteria) of all prior chemotherapy, immunotherapy, radiotherapy, or any other treatment modality prior to entering this study. 3.3 Chemotherapy Patients must have received their last dose of known myelosuppressive anticancer therapy at least 21 days prior to enrollment or at least 42 days if nitrosourea. 3.4 Investigational/Biologic Agent ●Biologic or investigational agent (anti-neoplastic): Patient must have recovered from any acute toxicity potentially related to the agent and received their last dose of the investigational or biologic agent ≥ 7 days prior to study enrollment. For agents that have known adverse events occurring beyond 7 days after administration, this period must be extended beyond the time during which adverse events are known to occur. ●Monoclonal Antibodies and agents with known prolonged half-lives: Patient must have recovered from any acute toxicity potentially related to the agent and received their last dose of the agent ≥ 28 days prior to study enrollment. 3.5 Radiation Patients must have had their last fraction of: * Craniospinal irradiation or total body irradiation or radiation to \> 50% of pelvis \> 3 months prior to enrollment. * Focal irradiation \> 4 weeks prior to enrollment 3.6 Stem Cell Transplant Patient must be: * ≥ 6 months since allogeneic stem cell transplant prior to enrollment with no evidence of active graft vs. host disease * ≥ 3 months since autologous stem cell transplant prior to enrollment 3.7 Growth Factors Patients must be off all colony-forming growth factor(s) for at least 1 week prior to enrollment (e.g. filgrastim, sargramostim or erythropoietin). Two weeks must have elapsed if patients received long-acting formulations. 3.8 Thrombopoietin receptor agonist * Phase I: Patients must be off thrombopoietin receptor agonists for at least 1 week prior to enrollment (e.g. romiplostim, eltrombopag) * Phase II: Patients can receive concurrent thrombopoietin receptor agonists 3.9 Somatostatin analogs Patients must be off long-acting somatostatin analogs for at least 4 weeks and off short-acting somastatin analogs (i.e., octreotide) for at least 24 hours. 3.10 Neurologic Status * Patients with neurological deficits should have deficits that are stable for a minimum of 1 week prior to enrollment, documented by a detailed neurological exam. * Patients with seizure disorders may be enrolled if seizures are well controlled. 3.11 Performance Status Karnofsky Performance Scale (KPS for \> 16 years of age) or Lansky Performance Score (LPS for ≤ 16 years of age) assessed within two weeks of enrollment must be ≥ 50. Patients who are unable to walk because of neurologic deficits, but who are up in a wheelchair, will be considered ambulatory for the purpose of assessing the performance score 3.12 Organ Function Patients must have adequate organ and marrow function, for eligibility and enrollment, as defined below: * Adequate Bone Marrow Function as defined as: * Absolute neutrophil count ≥ 1.0 x 109 cells/ L * Platelets ≥100 x 109 cells/ L (unsupported, defined as no platelet transfusion within 7 days) * Hemoglobin ≥8 g/dl (may receive transfusions) * Adequate Renal Function as defined as: * Creatinine clearance or radioisotope GFR \>70mL/min/1.7