Medulloblastomas are invasive and rapidly growing childhood central nervous system tumors that develop in the posterior fossa (containing the brain stem and cerebellum). Diagnosis is based on MRI and biopsy/tumor resection. Treatment is a combination of surgery, radiation therapy, and chemotherapy.
Medulloblastoma is the most common malignant posterior fossa tumor in children and the second most common malignant cancer of all pediatric central nervous system cancers (1). It has a bimodal peak at age 3 to 4 years and at age 8 to 10 years but can occur throughout childhood. Medulloblastoma is a type of central nervous system embryonal tumor.
Etiology of medulloblastoma is unknown in most patients, but medulloblastoma may occur with certain syndromes (eg, Gorlin syndrome, Turcot syndrome).
General reference
1. Ostrom QT, Price M, Neff C, et al: CBTRUS statistical report: Primary brain and other central nervous system tumors diagnosed in the United States in 2015-2019. Neuro Oncol 24(Suppl 5):v1–v95, 2022. doi: 10.1093/neuonc/noac202
Symptoms and Signs of Medulloblastoma
Patients present most commonly with symptoms associated with increased intracranial pressure and cerebellar dysfunction, which may include vomiting, headache, nausea, visual changes (eg, double vision), and unsteady walking or clumsiness.
Diagnosis of Medulloblastoma
MRI
Histologic evaluation of biopsy specimen or entire resected tumor
MRI with gadolinium contrast is the test of choice for initial evaluation of possible medulloblastoma. Definitive diagnosis is made using tumor tissue obtained by biopsy or ideally by gross total resection of the tumor at initial presentation.
Once the initial diagnosis is established, staging and risk group determination are critical in medulloblastoma.
Staging tests include
MRI of the entire spine
Lumbar puncture for cerebrospinal fluid cytology
Postoperative brain MRI to assess for any residual tumor
Risk assessment is based on amount of residual tumor and evidence of spread of disease:
High risk: Postoperative residual disease is > 1.5 cm2 or there is disseminated microscopic or gross disease.
Average risk: Postoperative residual disease is ≤ 1.5 cm2 and there is no dissemination.
Molecular grouping is also part of the diagnostic evaluation; treatments and risk assessment evolve based on these molecular features. The major molecular groups for medulloblastoma are WNT-activated, SHH-activated, group 3, and group 4. New subgroups with prognostic significance have emerged at a more granular level below the 4 major molecular groups.
(See also the World Health Organization's 2021 classification of tumors of the central nervous system.)
Treatment of Medulloblastoma
Surgery, radiation, and chemotherapy
Treatment of medulloblastoma includes surgery, radiation, and chemotherapy.
Cure with chemotherapy alone with regimens that avoid or delay radiation has occurred in some children < 3 years of age, usually in combination with surgery plus high-dose chemotherapy with autologous hematopoietic stem cell transplantation.
Combination therapy typically provides the best long-term survival.
Prognosis for Medulloblastoma
Prognosis depends on age, stage, histology, cytogenetics, and molecular parameters of the tumor (1):
Age > 3 years: Likelihood of 5-year disease-free survival is 60 to 70% if the tumor is high risk, and 80% if the tumor is average risk.
Age ≤ 3 years: Prognosis is more problematic, in part because up to 40% of children have disseminated disease at diagnosis and radiation therapy is typically avoided/delayed in this age group. Children who survive are at risk of severe long-term neurocognitive deficits (eg, in memory, verbal learning, and executive function).
Molecular group WNT-activated has the best prognosis with 90 to 100% overall survival. Ongoing pediatric clinical trials are being done to determine whether therapy can be reduced in patients with WNT-activated medulloblastoma (2).
Prognosis references
1. Ramaswamy V, Remke M, Bouffet E, et al. Risk stratification of childhood medulloblastoma in the molecular era: The current consensus. Acta Neuropathol. 2016;131(6):821–831. doi:10.1007/s00401-016-1569-6
2. Cohen KJ, Munjapara V, Aguilera D, et al. A Pilot Study Omitting Radiation in the Treatment of Children with Newly Diagnosed Wnt-Activated Medulloblastoma. Clin Cancer Res. 2023;29(24):5031-5037. doi:10.1158/1078-0432.CCR-23-0348
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
World Health Organization (WHO): The 2021 WHO Classification of Tumors of the Central Nervous System: A summary
