Medulloblastoma is the second-most frequent brain tumor in children after pilocytic astrocytoma and the most common malignant brain tumor in children, comprising 14.5% of newly diagnosed brain tumors. In adults, medulloblastoma is rare, comprising fewer than 2% of CNS malignancies.The rate of new cases of childhood medulloblastoma is higher in males (62%) than females (38%), a feature that is not seen in adults. Medulloblastoma and other PNET`s are more prevalent in younger children than older children. About 40% of medulloblastoma patients are diagnosed before the age of five, 31% are between the ages of 5 and 9, 18.3% are between the ages of 10 and 14, and 12.7% are between the ages of 15 and 19. Research models
Using gene transfer of SV40 large T-antigen in neuronal precursor cells of rats, a brain tumor model was established. The PNETs were histologically indistinguishable from the human counterparts and have been used to identify new genes involved in human brain tumor carcinogenesis. The model was used to confirm p53 as one of the genes involved in human medulloblastomas, but since only about 10% of the human tumors showed mutations in that gene, the model can be used to identify the other binding partners of SV40 Large T- antigen, other than p53. Recently a SHH-type mouse model with high incidence of medulloblastoma, a Patched 1 heterozygous mice knockout for the medulloblastoma suppressor Tis21 (Patched1+-/Tis21 KO). The high medulloblastoma frequency appears to be caused by the down regulation of Cxcl3, being Cxcl3 induced by Tis21.
The addition of radiation to the entire neuraxis and chemotherapy may increase the disease-free survival. Some evidence indicates that proton beam irradiation reduces the impact of radiation on the cochlear and cardiovascular areas and reduces the cognitive late effects of cranial irradiation. This combination may permit a 5-year survival in more than 80% of cases. The presence of desmoplastic features such as connective tissue formation offers a better prognosis. Prognosis is worse if the child is less than 3 years old, degree of resection is inadequate, or if any CSF, spinal, supratentorial, or systemic spread occurs. Dementia after radiotherapy and chemotherapy is a common outcome appearing two to four years following treatment. Side effects from radiation treatment can include cognitive impairment, psychiatric illness, bone growth retardation, hearing loss, and endocrine disruption. Increased intracranial pressure may be controlled with corticosteroids or a ventriculoperitoneal shunt. A new approach to monitor tumor development and treatment response by liquid biopsy is promising, but remains challenging. Chemotherapy
Chemotherapy is often used as part of treatment. Evidence of benefit, however, is not clear as of 2013. A few different chemotherapeutic regimens for medulloblastoma are used; most involve a combination of lomustine, cisplatin, carboplatin, vincristine, or cyclophosphamide. In younger patients (less than 3–4 years of age), chemotherapy can delay, or in some cases possibly even eliminate, the need for radiotherapy. However, both chemotherapy and radiotherapy often have long-term toxicity effects, including delays in physical and cognitive development, higher risk of second cancers, and increased cardiac disease risks.