Hyperfractionated Versus Conventionally Fractionated Radiotherapy in Standard Risk Medulloblastoma (PNET4)

Inclusion Criteria: * Age at diagnosis at least 4 years or 5 years (according to the policy of the National Brain Tumour Group) and less than 22 years. * Histologically proven medulloblastoma, including the following variants(WHO classification - 2000): classic medulloblastoma, nodular / desmoplastic medulloblastoma, melanotic medulloblastoma, medullomyoblastoma No CNS metastasis on MRI - supratentorial, arachnoid of the posterior fossa or spine. * No clinical evidence of extra-CNS metastasis * No tumour cells on the cytospin of lumbar CSF. Central Review of CSF cytology is recommended but not mandatory. It will be left to national policy. * Radiotherapy to start no more than 40 days after surgery. * Ability to receive twice daily radiotherapy. * Vital functions within normal range for their age group. * CTC grades \< 2 for liver, renal, haematological and audiological function. * No medical contraindication to radiotherapy or chemotherapy. * Written informed consent (and patient assent where appropriate) according to the laws of each participating country. Written informed consent should also be sought for biological studies. * National and local ethical committee approval according to the laws of each participating country (to include approval for biological studies). Exclusion Criteria: * One of the inclusion criteria is lacking. * Brainstem or supratentorial primitive neuroectodermal tumour. * Atypical teratoid rhabdoid tumour. * Medulloepithelioma. * Ependymoblastoma. * Large cell médulloblastoma. * Metastatic medulloblastoma (on CNS MRI and/or positive cytospin of postoperative lumbar CSF). * Patient previously treated for a brain tumour or any type of malignant disease. * Patients who are pregnant. * Females who are sexually active and not taking reliable contraception. * Known predisposition to medulloblastoma e.g. Gorlin's syndrome.