Childrens medulloblastoma is 10 times greater in children than adults.
Adult medulloblastoma is rare, only consisting of under 2% of adult central nervous system (CNS) cancers and less than 1% of brain tumors. There are typically about 0.5 per million per year.1
The higher the age bracket, the less chance of medulloblastoma occurring.2
Etiology:
There is currently no known risk factors for medulloblastoma, but genetics are being considered.
Signs &Symptoms:
Medulloblastoma symptoms include morning headaches, nausea, and vomiting.3 The common signs of a medulloblastoma tumor are a decrease in coordination, increase intracranial pressure, and abducens / oculomotor nerve defects.
Diagnostic Procedures:
A complete history and physical examination should be done on the patient.3
Cerebral spinal fluid (CSF) sampling should be performed.4
A spinal magnetic resonance (MR) scan should be performed.
A computed tomography (CT) scan may also be performed.
Histology:
Medulloblastomas are embryonal tumors.4 They arise from the primitive multipotential medulloblast, embryologically located in the external grandular layer of the cerebellum. It is an undifferentiated tumor, classically identified as a primitive neuroectodermal tumor (PNET) presenting in the posterior fossa. It is a specific undifferentiated embryonal neoplasm separate from classic embryonal tumors, with clear lines of differentiation.
Lymph node drainage:
These tumors are located within the central nervous system. This area does not have lymph nodes, and does not spread through lymphatic vasculature.4
Metastatic spread:
Medulloblastomas metastasize by “seeding” into the subarachnoid and ventricular spaces and in the spinal canal.4
Grading:
All primitive neuroectodermal tumors (PNET) of the brain are World Health Organization (WHO) grade IV because they are invasive with high growth rates.5
Staging:
Chang Staging System for Medulloblastoma6
Radiation side effects:
Acute and chronic side effects include:3
Hair loss
Erythema
Dry and moist desquamation
Edema
Drowsiness
Lethargy
Decreased mental status
Worsening of symptoms
Radiation necrosis
Cataracts
Prognosis:
The 5-year overall survival rates range from 58% to 84%. The recurrence rate for medulloblastomas in adults is approximately 50% to 60%.The median survival after recurrence has been reported to be approximately 1.3 years. The most common site of recurrence is the posterior fossa. Other sites of recurrence include the spine, CSF, supratentorial cerebrum, bone, and other extraneural sites. Late recurrences are more common in adults than in children. In one study, 59% of all recurrences occurred more than 2 years after treatment, whereas, in general, 75% of childhood medulloblastoma recurrences occur within the first 2 years after treatment. Recurrences as late as 14 years after treatment have been reported. Thus, long-term monitoring is important for adult medulloblastoma patients.7
Treatments:
Surgery, radiation therapy and chemotherapy
The goal of surgery is to remove all visible tumor. Survival of adult medulloblastoma patients may be influenced by the extent of residual disease following surgery, particularly for patients without evidence of dissemination. Treatment of associated hydrocephalus can be managed by external drainage with tumor decompression, tumor decompression alone, or by the use of various shunting procedures. Craniospinal axis radiation therapy is the standard of care for the treatment of adult medulloblastoma patients, as medulloblastomas are quite radiosensitive. Standard radiation doses to the craniospinal axis involve delivering 35 to 45 gray (Gy) to the brain and 30 to 40 Gy to the spine, with a dose of 54 Gy to the primary tumor site. Long-term adult medulloblastoma survivors who were previously treated with whole-brain radiation were found to have below-average IQs and notable deficits in memory, visuospatial skills, reasoning, and arithmetic.7
TD 5/5:
The table below shows the tolerance dose to an organ based on giving the dose in one fraction or fractionated, using TD5/5 (5% chance of injury showing up over the next 5 years) and TD50/5 (50% chance of an injury).1 The specific organs for this type of treatment would include the eyes, lens, brain, and possibly spinal cord.
Chang Staging System for Medulloblastoma6
The goal of surgery is to remove all visible tumor. Survival of adult medulloblastoma patients may be influenced by the extent of residual disease following surgery, particularly for patients without evidence of dissemination. Treatment of associated hydrocephalus can be managed by external drainage with tumor decompression, tumor decompression alone, or by the use of various shunting procedures.
Craniospinal axis radiation therapy is the standard of care for the treatment of adult medulloblastoma patients, as medulloblastomas are quite radiosensitive. Standard radiation doses to the craniospinal axis involve delivering 35 to 45 gray (Gy) to the brain and 30 to 40 Gy to the spine, with a dose of 54 Gy to the primary tumor site. Long-term adult medulloblastoma survivors who were previously treated with whole-brain radiation were found to have below-average IQs and notable deficits in memory, visuospatial skills, reasoning, and arithmetic.7
http://www.aboutcancer.com/radiation_dose1.gif
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