Reduced Craniospinal Radiation Therapy and Chemotherapy in Treating Younger Patients With Newly Diagnosed WNT-Driven Medulloblastoma

PRIMARY OBJECTIVE: I. To estimate the progression-free survival (PFS) of children \>= 3 years of age with wingless-type MMTV integration site family (WNT)-driven average-risk medulloblastoma using reduced craniospinal radiotherapy (CSI) (18 Gray \[Gy\]) with a limited target volume boost to the tumor bed of 36 Gy for a total of 54 Gy and reduced chemotherapy approach (no vincristine \[vincristine sulfate\] during radiotherapy and reduced-dose maintenance chemotherapy) and to monitor the PFS for early evidence that the outcome is unacceptable. SECONDARY OBJECTIVES: I. To prospectively test the hypothesis that deoxyribonucleic acid (DNA) methylation profiling will accurately classify WNT-driven medulloblastoma. II. To prospectively evaluate and longitudinally model the cognitive, social, emotional, behavioral, and quality of life (QoL) functioning of children who are treated with reduced CSI (18 Gy) with a limited target volume boost to the tumor bed (to a total of 54 Gy) and reduced chemotherapy (reduced cisplatin, vincristine, and lomustine \[CCNU\]). EXPLORATORY OBJECTIVES: I. To explore whether DNA methylation profiling of medulloblastoma samples will result in a predictive classification scheme for the Sonic Hedgehog (SHH), Group 3, and Group 4 medulloblastoma subgroups according to the Heidelberg classifier. This will be addressed in a separate biology protocol. II. To describe the audiologic and endocrinologic toxicities, as well as peripheral neuropathy, in children treated with reduced CSI (18 Gy) with a limited target volume boost to the tumor bed (to a total of 54 Gy) and reduced cisplatin and vincristine chemotherapy. OUTLINE: RADIATION THERAPY: Beginning 4-5 weeks after surgery, patients undergo craniospinal radiation therapy 5 days a week for 6 weeks. MAINTENANCE THERAPY (WEEKS 1, 3, 5, and 7): Beginning 4-6 weeks after completion of radiation therapy patients receive lomustine orally (PO) on day 1, vincristine sulfate intravenously (IV) via minibag on days 1, 8, and 15, and cisplatin IV over 6 hours on day 1. Treatment repeats every 42 days in the absence of disease progression or unacceptable toxicity. MAINTENANCE THERAPY (WEEKS 2, 4, AND 6): Patients receive cyclophosphamide IV over 30-60 minutes on days 1 and 2, mesna IV over 15-30 minutes on days 1 and 2, and vincristine sulfate IV via minibag on days 1 and 8. Treatment repeats every 28 days in the absence of disease progression or unacceptable toxicity. Patients also undergo magnetic resonance imaging (MRI) throughout the trial. After completion of study treatment, patients are followed up every 3 months for 2 years, every 6 months for 2 years, and then annually for 6 years.