Surgery : Maximal debulking surgery will be performed to minimize tumor burden and confirm diagnosis of recurrent tumor. All tumors will be confirmed as recurrent MB/PNET by a board- eligible/board -certified neuropathologist. Tumor tissue in excess of what is needed to confirm pathologic diagnosis will be transported under aseptic precautions to Dr. Mitchell’s laboratory for tum or RNA preparation. Tumor tissue may also be obtained through biopsy or CSF (cytology). Patients will undergo a non- mobilized leukapheresis prior to salvage chemotherapy for harvest of peripheral blood mononuclear cells (PBMCs) for TTRNA -xALT and TTRNA -DC generation. The target PBMC count based on the desired dose of TTRNA -xALT and sufficient TTRNA -DCs for T cell expansion and in vivo vaccination will be collected. Following standard salvage chemotherapy adequate organ function testing will be repeated pri or to initiation of NMA chemotherapy ( cyclophosphamide and fludarabine conditioning ) as described below: • Bone Marrow function: - Absolute neutrophil count > 1000/µl (unsupported) * - Platelets > 100,000/µl (unsupported) * - Hemoglobin > 8 g/dL (may be supported) * Patients on Group B with ANC <1000/µL and/or platelet count <100,000/µL prior to NMA will be allowed to get vaccine and ALT infusion; however, NMA conditioning will be withheld . • Renal: - Serum creatinine ≤ upper limit of institutional normal and/or GFR > 70 ml/min/1.73m 2 - If GFR < 70 ml/min/1.73 m2, Fludarabine dose adjusted for GFR < 70 ml/min/1.73m2 per drug guidelines • Hepatic: - Bilirubin ≤ 1.5 times upper limit of normal for age. - SGPT (ALT) ≤ 3 times institutional upper limit of normal for age. - SGOT (AST) ≤ 3 times institutional upper limit of normal for age. • Adequate cardiac function defined as: - ECHO cardiogram with an e jection fraction of > 45% or MUGA scan within normal l imits - Patients in Group B will be eligible if the ejection fraction is < 45% but will receive Fludarabine only during NMA conditioning prior to vaccine + ALT infusion. • Pulmonary: -- DLCO, FEV1, FEC (diffusion capacity) > 50% of predicted (corrected for hemoglobin and alveolar volume) or - Chest X -ray and pulse oximetry reading of > 93% in room air at rest and following a brisk 6- minute exercise resulting in a target heart rate of at least 100/min. - Patients in Group B who do not meet thi s requirement will still be eligible but will receive Fludarabine only during NMA conditioning. • Negative serum pregnancy test for females of child -bearing potential. Of note, cyclophosphamide will be withheld if a patient does not meet the cardiac performance criteria and lymphodepletive conditioning will proceed with fludarabine only. Additionally, the fludarabine dose may be modified for GFR < 70 ml/min/1. 73m 2. Refer to Section 18.8 Fludarabine Phosphate for dose modification guidelines . Re-MATC H Protocol Page 58 of 106 Version: 20180628 NMA salvage chemotherapy will consist of 28 -day cycles until Immunotherapy preparation is complete . The drugs will be given on the following schedule: Re-MATC H Protocol Page 59 of 106 Version: 20180628 After completion of NMA salvage chemotherapy and starting 11 days before Immunotherapy , patients will receive 2 days of cyclophosphamide IV at 1 g/m 2, followed by 5 days of fludarabine IV at 25 mg/m2 (dose may be modified for GFR < 70 ml/min/1.73m2. Refer to Section 18.8 for dose modification guidelines ). Approximately 72 hours following fludarabine, PBSCs , if available, will be infused. Approximately 96 hours following the final dose of fludarabine, Immunotherapy will begin with infusion of the TTRNA -xALT and injection of the first TTRNA -DC vaccine. Patients will receive 3 biweekly vaccines as long as clinically stable. Drug Name Route Dose Schedule Temozolomide PO 150 mg/m2/day Days 1-5 Etoposide PO 30 mg/m2/day Days 1-14 Filgrastim (G -CSF) IV or SQ 10 micrograms/ kg/day Starting Day 15 *administered each cycle until enough CD34 cells are harvested ( goal of 2x10 6/kg) for infusion Re-MATC H Protocol Page 60 of 106 Version: 20180628 Drug Name Route Dose Schedule Instructions for administration Cyclophosphamide IV 1000 mg/m2/day Days 1 & 2 Dose reduce or omit based on cardiac and/or pulmonary function Fludarabine IV 25 mg/m2/day Days 3 -7 Dose reduce or omit based on creatinine clearance Peripheral Blood Stem Cells , if available IV A minimum of 2x106 CD34+ cells/kg or all available cells if < 2x10 6 CD34+ cells/kg Day 10 IV through central venous catheter per institutional guidelines TTRNA -xALT IV 3x107cells/kg or all available cells Day 11 IV over 10-30 minutes through central venous catheter . Pre-medicate 30 -60 minutes prior to infusion with acetaminophen ( up to 10- 15 mg/kg/dose) and Benadryl ( up to 1 mg/kg) to reduce infusion -related reactions.