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.
Inclusion Criteria:
* Patients must be greater than or equal to 3 years and less than 22 years of age at the time of enrollment
* Patients must be newly diagnosed and have:
* Eligibility confirmed by rapid central pathology and molecular screening review on APEC14B1:
* Classical histologic type (non LC/A) WNT medulloblastoma
* Positive nuclear beta-catenin by immunohistochemistry (IHC)
* Positive for CTNNB1 mutation by Sanger sequencing
* Negative for MYC and MYCN by fluorescence in situ hybridization (FISH)
* Patient must have negative lumbar cerebrospinal fluid (CSF) cytology
* Note: CSF cytology for staging should be performed no sooner than 14 days post operatively to avoid false positive CSF; ideally, CSF should be obtained between day 14 and day 21 to allow for final staging status before enrollment onto the study; patients with positive CSF cytology obtained 0 to 14 days after surgery should have cytology repeated to determine eligibility and final CSF status; patients with negative CSF cytology from lumbar puncture obtained 0 to 14 days after surgery do not need cytology repeated; patients with negative CSF cytology from lumbar puncture obtained prior to surgery do not need cytology repeated post-operatively
* Patients must have eligibility confirmed by Rapid Central Imaging Review on APEC14B1; patients must have =\< 1.5 cm\^2 maximal cross-sectional area of residual tumor; whole brain magnetic resonance imaging (MRI) with and without gadolinium and spine MRI with gadolinium must be performed
* Patients must be enrolled, and protocol therapy must be projected to begin, no later than 36 days after definitive diagnostic surgery (day 0)
* Peripheral absolute neutrophil count (ANC) \>= 1000/uL
* Platelet count \>= 100,000/uL (transfusion independent)
* Hemoglobin \>= 8.0 g/dL (may receive red blood cell \[RBC\] transfusions)
* Creatinine clearance or radioisotope glomerular filtration rate (GFR) \>= 70 mL/min/1.73 m\^2 or a serum creatinine based on age/gender as follows:
* 3 to \< 6 years of age: maximum (max) serum creatinine 0.8 mg/dL (males and females)
* 6 to \< 10 years of age: max serum creatinine 1 mg/dL (males and females)
* 10 to \< 13 years of age: max serum creatinine 1.2 mg/dL (males and females)
* 13 to \< 16 years of age: max serum creatinine 1.5 md/dL (males) and 1.4 md/dL (females)
* \>= 16 years of age: max serum creatinine 1.7 mg/dL (males) and 1.4 mg/dL (females)
* The threshold creatinine values were derived from the Schwartz formula for estimating GFR utilizing child length and stature data published by the Centers for Disease Control and Prevention (CDC)
* Total or direct bilirubin =\< 1.5 x upper limit of normal (ULN) for age, and
* Serum glutamate pyruvate (SGPT) (alanine aminotransferase \[ALT\]) =\< 135 U/L (3x ULN); for the purpose of this study, the ULN for SGPT is 45 U/L
* Central nervous system function defined as:
* Patients with seizure disorder may be enrolled if on anticonvulsants and well controlled
* Patients must not be in status epilepticus, a coma or on assisted ventilation at the time of study enrollment
* Patients must have receptive and expressive language skills in English, French, or Spanish to complete the QoL and neurocognitive assessments; if a patient meets these criteria but the parent/guardian speaks a language other than English, French, or Spanish, the patient may still be enrolled and tested, and the parent-report measures should be omitted
* All patients and/or their parents or legal guardians must sign a written informed consent; assent, when appropriate, will be obtained according to institutional guidelines
* All institutional, Food and Drug Administration (FDA), and National Cancer Institute (NCI) requirements for human studies must be met
Exclusion Criteria:
* Patients with metastatic disease by either MRI evaluation (brain and spine) or lumbar CSF cytology are not eligible; patients who are unable to undergo a lumbar puncture for assessment of CSF cytology are ineligible
* Patients must not have received any prior radiation therapy or chemotherapy (tumor-directed therapy) other than surgical intervention and/or corticosteroids
* Pregnancy and Breast Feeding
* Female patients who are pregnant are ineligible due to risks of fetal and teratogenic adverse events as seen in animal/human studies
* Lactating females are not eligible unless they have agreed not to breastfeed their infants
* Female patients of childbearing potential are not eligible unless a negative pregnancy test result has been obtained
* Sexually active patients of reproductive potential are not eligible unless they have agreed to use an effective contraceptive method for the duration of their study participation
* Patients with a history of moderate to profound intellectual disability (i.e., intelligence quotient \[Q)\]=\< 55) are not eligible for enrollment; PLEASE NOTE: Children with a prior history of attention deficit hyperactivity disorder (ADHD) or a specific learning disability (e.g., dyslexia) are eligible for this study. Children with posterior fossa syndrome (also known as cerebellar mutism) are eligible for this study
