PDQ® Treatment Health Professionals
This treatment information summary on childhood medulloblastoma is an overview of prognosis, diagnosis, classification, and patient treatment. The National Cancer Institute created the PDQ database to increase the availability of new treatment information and its use in treating patients. Information and references from the most recently published literature are included after review by pediatric oncology specialists.
Primary brain tumors are a diverse group of diseases that together constitute the most common solid tumor of childhood. Brain tumors are classified according to histology, but tumor location and extent of spread are important factors that affect treatment and prognosis. Immunohistochemical analysis, cytogenetic and molecular genetic findings, and measures of mitotic activity have been used in the tumor diagnosis and classification.
Approximately 50% of brain tumors in children are infratentorial, with three fourths of these located in the cerebellum or fourth ventricle. Common infratentorial (posterior fossa) tumors include the following:
2. medulloblastoma (primitive neuroectodermal tumor)
4. brain stem glioma (often diagnosed neuroradiographically without biopsy; may be high- or low-grade)
2. diencephalic (chiasm, hypothalamic, and/or thalamic) gliomas generally of low grade
2. high-grade or malignant astrocytoma (anaplastic astrocytomas, glioblastomas multiforme (grade 3 or grade 4))
3. mixed glioma
5. primitive neuroectodermal tumor (cerebral neuroblastoma)
8. choroid plexus tumors (papilloma and carcinoma)
9. pineal parenchymal tumors (pineoblastoma, pineocytoma, or mixed pineal parenchymal tumor)
10. neuronal and mixed neuronal glial tumor (ganglioglioma, desmoplastic infantile ganglioglioma, dysembryoplastic neuroepithelial tumor)
2. Children with primary brain tumors represent a major therapy challenge that, for optimal results, requires the coordinated efforts of pediatric specialists in fields such as neurosurgery, neurology, rehabilitation, neuropathology, radiation oncology, medical oncology, neuroradiology, endocrinology, and psychology, who have special expertise in the care of patients with these diseases.[1-3]
3. More than one half of children diagnosed with brain tumors will survive 5 years from diagnosis. In some subgroups of patients, an even higher rate of survival and cure is possible. Each child's treatment should be approached with curative intent, and the possible long-term sequela of the disease and its treatment should be considered when therapy is begun.
4. For the majority of childhood brain tumors, the optimal treatment regimen has not been determined. Children who have brain tumors should be considered for enrollment in clinical trials when an appropriate study is available. Such clinical trials are being carried out by institutions and cooperative groups. In the United States, the two major cooperative groups are the Pediatric Oncology Group and the Childrens Cancer Group.
5. Guidelines for pediatric cancer centers and their role in the treatment of pediatric patients with cancer have been outlined by the American Academy of Pediatrics.
For information on current clinical trials for children with brain tumors, consult the PDQ Protocol File.
The classification of brain tumors is based on both histopathological characteristics and location in the brain. Undifferentiated neuroectodermal tumors of the cerebellum have historically been referred to as medulloblastomas, while tumors of identical histology in the pineal region are diagnosed as pineoblastomas. Pineoblastoma and medulloblastoma are very similar but not identical. The nomenclature of pediatric brain tumors is controversial and potentially confusing. Some pathologists advocate abandoning the traditional morphologically based classifications such as medulloblastoma in favor of a terminology that relies more extensively on the phenotypic characteristics of the tumor. In such a system, medulloblastoma is referred to as primitive neuroectodermal tumor and then subdivided on the basis of cellular differentiation.[1-4] The most recent World Health Organization classification of brain tumors maintains the term "medulloblastoma" for posterior fossa undifferentiated tumors. It also maintains separate categories for cerebral primitive neuroectodermal tumors and for pineal small round cell tumors (pineoblastomas). The pathologic classification of pediatric brain tumors is a specialized area that is undergoing evolution; review of the diagnostic tissue by a neuropathologist who has particular expertise in this area is strongly recommended.
This tumor usually originates in the cerebellum. It may spread contiguously to the cerebellar peduncle, floor of the fourth ventricle, into the cervical spine, or above the tentorium. In addition, it may spread via the cerebrospinal fluid intracranially and/or to the spinal cord. Every patient with medulloblastoma should be evaluated with diagnostic imaging of the spinal cord and whole brain. The most sensitive method available for evaluating spinal cord subarachnoid metastasis is spinal magnetic resonance imaging (MRI) performed with gadolinium. If MRI is used, the entire spine must be imaged in at least two planes with contiguous MR slices performed after gadolinium enhancement. Because medulloblastoma occasionally metastasizes outside the central nervous system, especially to bone, a bone scan with plain film correlation as well as a bone marrow aspiration and biopsy may be useful in symptomatic patients or in those with abnormal blood cell counts. Cerebrospinal fluid shunts at the time of surgery have not been shown to increase the risk of leptomeningeal relapse. Until recently, the most commonly used staging system was that proposed by Harisiadis and Chang. This system rates the tumor by an intraoperative evaluation of both size and extent as well as by the presence of metastatic disease. Alternative postoperative staging systems are now being used that are based on surgical impression and postoperative imaging studies. Patients with disseminated disease at diagnosis are clearly at highest risk for disease relapse. Other factors that may portend an unfavorable outcome include younger age at diagnosis, brain stem involvement, subtotal resection, and a nonposterior fossa tumor.[1-3] The prognostic importance of brain stem involvement is still being debated. These prognostic variables must be evaluated in the context of the treatment received. Biologic markers, such as tumor-cell ploidy, are also being evaluated and the subcategories of disease may change over time.[4-7] Two major subclassifications are now being used:
Many of the improvements in survival in childhood cancer have been made as a result of clinical trials that have attempted to improve on the best available, accepted therapy. Clinical trials in pediatrics are designed to compare new therapy with therapy that is currently accepted as standard. This comparison may be done in a randomized study of two treatment arms or by evaluating a single new treatment and comparing the results with those previously obtained with existing therapy.
Because of the relative rarity of cancer in children, all patients with brain tumors should be considered for entry into a clinical trial. To determine and implement optimum treatment, treatment planning by a multidisciplinary team of cancer specialists who have experience treating childhood brain tumors is required. Radiation therapy of pediatric brain tumors is technically very demanding and should be carried out in centers that have experience in that area in order to ensure optimal results.
In the past, treatment has included surgery with radiation therapy. There is evidence to suggest that more extensive surgical resections are related to an improved rate of survival, primarily in children with nondisseminated posterior fossa disease at diagnosis. Chemotherapy has been shown to be active in patients with recurrent medulloblastomas. Prospective, randomized trials and large single-arm trials suggest that adjuvant chemotherapy given during and after radiation therapy may improve overall survival for the subset of children with medulloblastoma who have less favorable prognostic factors, and there has been enthusiasm for exploring the role of chemotherapy in the treatment of childhood brain tumors.[1-3] Children younger than 3 years of age are particularly susceptible to the adverse effect of radiation on brain development. Debilitating effects on growth and neurologic development have frequently been observed, especially in younger children.[4,5] For this reason, the role of chemotherapy in allowing a delay in the administration of radiation therapy is under study, and preliminary results suggest that chemotherapy can be used to delay, and sometimes obviate, the need for radiation therapy in children with medulloblastoma.[1,6] Surveillance testing is presently a part of all ongoing medulloblastoma studies. Secondary tumors have increasingly been diagnosed in long-term survivors.[8,9] Long-term management of these patients is complex and requires a multidisciplinary approach.
The designations in PDQ that treatments are "standard" or "under clinical evaluation" are not to be used as a basis for reimbursement determinations.
Careful evaluation to determine fully the extent of disease must precede the treatment of medulloblastoma. Surgery should be an attempt at maximal tumor reduction; children without disseminated disease at diagnosis have improved progression-free survival if there is minimal residual disease present after surgery. Postoperatively, studies should be conducted to determine if the patient has high risk of relapse. Risk criteria are outlined in the stage information section.[2,3] Patients with extensive tumor should be considered at "high risk" for relapse and be treated on protocols specifically designed for them.
The traditional postsurgical treatment for these patients has been radiation therapy consisting of 5,400-5,580 cGy to the tumor bed and approximately 3,600 cGy to the entire neuraxis (i.e., the whole brain and spine). The minimal dose of radiation therapy needed for disease control is unknown. Attempts to lower the dose of craniospinal radiation therapy to 2,340 cGy have resulted in an increased incidence of isolated leptomeningeal relapse. Studies are ongoing to determine if a lower dose of radiation therapy, when coupled with chemotherapy, can be used to control disease. Craniospinal irradiation is technically extremely demanding. Less than optimal techniques have resulted in failure at the junction of the brain and spine fields or in the cribriform plate region. When possible, patients should be treated in a center experienced with this therapy. There is no evidence that adjuvant chemotherapy improves the outcome for patients with average-risk medulloblastoma. However, trials are ongoing to evaluate the possible role of reduced-dose radiation therapy and chemotherapy in these patients. Consult PDQ for information on clinical trials.
In poor-risk patients, the addition of chemotherapy has improved the duration of disease-free survival. Some studies show that approximately 50%-60% of such patients will experience long-term disease control. These are patients who, at diagnosis, have locally extensive and often unresectable tumor in the posterior fossa, brain stem involvement at diagnosis, and/or noncontiguous metastatic disease within or outside of the central nervous system. Adjuvant chemotherapy has improved progression-free survival for patients with these "poor-risk" parameters at diagnosis.[2,6] Such patients should be considered for entry into a clinical trial.[2,3] Consult PDQ for information on current clinical trials.
Children younger than 3 years of age:
Some patients younger than 3 years of age with newly diagnosed medulloblastoma will respond, at least partially, to chemotherapy. Some patients, especially those with minimal residual postoperative disease, may have a long-lasting response.[3,7] For this reason, strong consideration should be given to entering patients younger than 3 years of age in studies that use chemotherapy to delay, modify, or possibly obviate the need for radiation therapy. High-dose chemotherapy with autologous bone marrow rescue followed by focal radiation therapy has been used with some success in young children with locally recurrent disease for whom primary chemotherapy has failed. Although chemotherapy is being used to prevent neurologic damage caused by radiation therapy in very young patients, neurologic deficits may be present in children prior to the initiation of therapy, and progressive neurologic damage has been noted during therapy.
Recurrence is not uncommon in both benign and malignant childhood brain tumors and may develop many years after initial treatment. Disease may recur at the primary tumor site or, especially in malignant tumors, at noncontiguous central nervous system sites. Systemic relapse is rare, but may occur. At time of relapse, a complete evaluation for extent of recurrence is indicated for all malignant tumors and, at times, for more benign lesions. Biopsy or surgical resection may be necessary for confirmation of relapse because other entities such as secondary tumor and treatment-related brain necrosis may be clinically indistinguishable from tumor recurrence. The need for surgical intervention must be individualized on the basis of the initial tumor type, the length of time between initial treatment and the reappearance of the lesion, and the clinical picture. Patients with medulloblastoma that recurs after radiation therapy alone should be considered for treatment with known active agents, which include vincristine, cyclophosphamide, cisplatin, carboplatin, lomustine, and etoposide; although response is seen in more than 50% of patients, long-term disease control is rare.[2-4] Entry into studies of novel therapeutic approaches including high-dose chemotherapy and autologous stem cell rescue at the time of relapse after radiation therapy alone or radiation therapy and chemotherapy should be considered.[5-7] Consult PDQ for information on current clinical trials.
Date Last Modified: 08/1999