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Medulloblastoma in Children and Teens

What is Medulloblastoma?

Medulloblastoma is the most common malignant brain tumor in children. Medulloblastoma begins in the cerebellum, an area in the back of the brain.

What is Medulloblastoma? Medulloblastoma is a brain tumor of the cerebellum. The cerebellum is found in a region of the brain called the posterior fossa.

Medulloblastoma is a brain tumor of the cerebellum. The cerebellum is found in a region of the brain called the posterior fossa.

There are about 500 new cases of pediatric medulloblastoma every year in the United States. They account for 20% of childhood central nervous system (CNS) tumors. Medulloblastoma is most common in children under 16 years of age. It is most often diagnosed between 5 and 9 years of age. However, medulloblastoma may be seen in older teens and, less commonly, in adults.

Medulloblastoma can be divided into four subgroups based on molecular features of tumor cells:

  1. WNT subtype, pronounced “wint”
  2. SHH subtype, also known as Sonic hedgehog (SHH) medulloblastoma
  3. Group 3 medulloblastoma
  4. Group 4 medulloblastoma

The specific subgroup influences medulloblastoma prognosis. Doctors use subgroups to classify patients into risk categories. This information helps doctors plan appropriate treatments.

Treatment for medulloblastoma includes surgery to remove as much of the tumor as possible. Radiation therapy is used after surgery to kill any remaining cancer cells. Chemotherapy is also used together with surgery and radiation therapy.

Medulloblastomas are fast growing, and these tumors often spread to other parts of the brain and spinal cord. The overall survival rate for childhood medulloblastoma is 70-80% if the disease has not spread. If the disease has spread, the survival rate is about 60%. However, the specific type of medulloblastoma, including molecular subgroup, can influence treatment and prognosis.

Medulloblastoma can be divided into four subgroups based on molecular features of tumor cells: WNT subtype (pronounced “wint”), SHH subtype (also known as Sonic hedgehog medulloblastoma), Group 3, and Group 4.

Medulloblastoma can be divided into four subgroups based on molecular features of tumor cells: WNT subtype (pronounced “wint”) makes up 10% of cases, SHH subtype (also known as Sonic hedgehog medulloblastoma) makes up 30% of cases, Group 3 makes up 25% of cases, and Group 4 makes up 35% of cases.

Symptoms of Medulloblastoma

Signs and symptoms of medulloblastoma depend on several factors including the size and location of the tumor and the child’s age and stage of development.

Medulloblastoma symptoms include:

  • Headache, which is often worse in the morning or improves after vomiting
  • Nausea and vomiting
  • Fatigue or changes in activity levels
  • Dizziness
  • Loss of balance, clumsiness
  • Problems with handwriting
  • Change in vision

If the tumor has spread to the spinal cord, symptoms may include:

  • Back pain
  • Problems walking
  • Problems urinating or change in bowel function

Symptoms of medulloblastoma depend on tumor size and location. Medulloblastoma is a cerebellar tumor. The cerebellum is found in the lower rear part of the brain, in a region known as the posterior fossa. Functions of the cerebellum include the control of movement, balance, posture, and coordination.

Most medulloblastomas develop in the middle of the cerebellum by the fourth ventricle. As the tumor grows, it can block the normal flow of cerebrospinal fluid. This causes a buildup of fluid within the brain known as hydrocephalus. The fluid increases pressure on the brain (intracranial pressure). Many of the symptoms of medulloblastoma are due to hydrocephalus.

Risk Factors for Medulloblastoma

Certain gene and chromosome changes within the tumor cell are associated with the development of medulloblastoma. Usually, it is not known why these genetic changes occur.

Most medulloblastomas occur in children between ages 5 and 9 years old. It is rare in infants and adults. Medulloblastoma is slightly more common in boys than in girls.

Some children may be at increased risk for brain tumors due to rare inherited conditions or genetic disorders. These syndromes include Gorlin syndrome, Turcot syndrome, and Li-Fraumeni syndrome.

Diagnosis of Medulloblastoma

Doctors evaluate medulloblastoma in several ways.

  • A physical exam and medical history help doctors learn more about symptoms, general health, past illnesses, and risk factors.
  • A neurological exam examines the function of the brain, spinal cord, and nerves. These tests measure different aspects of functioning including memory, vision, hearing, muscle strength, balance, coordination, and reflexes.
  • Imaging tests are used to help identify the tumor. Magnetic resonance imaging (MRI) of the brain is the main imaging technique used to evaluate medulloblastoma. An MRI is also done after surgery to see if any tumor remains and to look for spread of disease.
  • A lumbar puncture may be performed after surgery to look for cancer cells in the cerebrospinal fluid (CSF). About 1/3 of medulloblastomas spread through the CSF to other parts of the brain or spinal cord.
  • Tissue from the tumor is examined to diagnose medulloblastoma. After the tumor is removed during surgery, a pathologist looks at the tissue sample under a microscope to identify cell features such as size and shape. This information can help doctors identify the specific type of medulloblastoma, classify patients by risk, and plan appropriate treatments.
MRI scan with markings showing medulloblastoma in the cerebellum.

MRI scan with markings showing medulloblastoma in the cerebellum.

Medulloblastoma shown in axial MRI. Medulloblastoma is the most common malignant brain tumor in children.

Medulloblastoma shown in axial MRI. Medulloblastoma is the most common malignant brain tumor in children.

Classification and Types of Medulloblastoma

Medulloblastoma can be classified or described based on certain features such as histology, molecular features, and metastasis. Tissue histology, molecular features of the tumor cells, and stage are used to categorize patients with medulloblastoma based on disease risk and prognosis. This helps doctors match treatment plans to medulloblastoma risk group.

Medulloblastoma Histology

Microscopic features of the tumor cells such as the size and shape are used to classify medulloblastoma tumors by histology:

  • Classic medulloblastoma is made up of small, round cells. The cells are close together and have dark nuclei.
  • Desmoplastic/nodular medulloblastoma appears as circular nodules ringed by connective tissue with cells closely packed together.
  • Medulloblastoma with extensive nodularity (MBEN) shows more nodular regions within the tissue.
  • Anaplastic medulloblastoma is made up of cells that are irregularly shaped.
  • Large cell medulloblastoma has tumor cells with large nuclei.

Anaplastic and large cells often occur together and are grouped as large cell anaplastic (LCA) tumors.

Molecular Subgroups of Medulloblastoma

Tissue from the tumor is also tested to learn about the genetic and molecular features of the tumor cells. Based on the molecular profile, medulloblastomas are grouped as WNT, SHH, Group 3, or Group 4.

Where the medulloblastoma tumor is located within the cerebellum can also provide a clue as to the molecular type of medulloblastoma. WNT medulloblastoma tumors tend to occur along the midline of the cerebellum. SHH medulloblastoma tumors tend to be found in the lateral part of the cerebellum.

Medulloblastoma Staging

Medulloblastoma may also be classified by metastasis, or spread of disease:

  • M0: The tumor is localized with no spread of disease.
  • M1: Tumor cells are found in the cerebrospinal fluid (CSF).
  • M2: There is evidence of spread of disease within the brain (intracranial).
  • M3: The tumor has spread to the spine.
  • M4: The tumor has spread outside the central nervous system (CNS). Common sites for metastases include the bones, lungs, and liver.

Medulloblastoma Prognosis

The overall five-year survival rate for pediatric medulloblastoma is approximately 70-80% if the disease has not spread. For high risk patients, the survival rate is about 60-65%.

Factors that affect chance of cure include:

  • Medulloblastoma histology
    • Children under 3 years of age: Desmoplastic tumors are associated with a better outcome compared to classic or LCA tumors.
    • Children over 3 years of age: Desmoplastic or classic tumors are associated with a better outcome compared to LCA tumors.
  • Molecular subtype of medulloblastoma. Features of the tumor and changes in genes or chromosomes including medulloblastoma subtype (WNT, SHH, Group 3, or Group 4) influence risk category. WNT tumors have a very good prognosis. SHH and Group 4 medulloblastoma tumors are considered intermediate risk. Group 3 medulloblastoma tumors have a worse prognosis.
  • Whether the cancer has spread. Medulloblastoma that has metastasized or spread to other parts of the brain or spinal cord is harder to treat. Localized medulloblastoma is associated with a better prognosis.
  • If surgery can completely remove the tumor. Children who have no visible tumor after surgery (gross total resection) have a better chance of cure.
  • Age at diagnosis. The influence of age on medulloblastoma prognosis depends on the medulloblastoma subgroup and other features. However, radiation therapy is not usually used in infants and young children under 3 years of age.
  • If the cancer is new or if it has come back. Recurrent medulloblastoma is associated with worse outcomes.

Types of Medulloblastoma and Prognosis

  WNT subtype SHH subtype Group 3 Group 4
% of Cases 10% of medulloblastomas 30% of medulloblastomas 25% of medulloblastomas 35% of medulloblastomas
Patient Characteristics Most common in older children and teens; rare in infants Most common in young children under 3 years of age and in older teens and adults Most common in Infants and young children; rare in teens; more common in males Found in all age groups but rare in infants; more common in males
Medulloblastoma Histology • Classic (most often)
• Large Cell Anaplastic (rare)
• Desmoplastic / nodular
• MBEN
• Classic
• Large Cell Anaplastic
• Classic
• Large Cell Anaplastic
• Classic
• Large Cell Anaplastic (rare)
Metastasis at Diagnosis 5-10% of patients have metastatic disease at diagnosis 15-20% of patients have metastatic disease at diagnosis 30-45% of patients have metastatic disease at diagnosis 35-40% of patients have metastatic disease at diagnosis
Recurrence Rarely recurs If it recurs, it is usually local disease If it recurs, it is usually metastatic If it recurs, it is usually metastatic
5-year Survival Rates for Medulloblastoma >90% survival 75% survival 50% survival 75% survival
Overall Medulloblastoma Prognosis Very good Intermediate, but infants have a better prognosis Poor Intermediate

Treatment of Medulloblastoma

Medulloblastoma treatment includes surgery, radiation to the brain and spine (except in children under 3 years of age), and chemotherapy.

Current risk-based approaches to medulloblastoma treatment classify patients based on tumor features and predicted outcomes. Doctors consider:

  • Molecular subgroup of medulloblastoma
  • Whether surgery completely removed the tumor
  • Whether the tumor has spread (metastatic disease)
  • Tumor histology
  • Genetic features of the tumor

The goal of a risk-based approach is to achieve survival while lowering the risk of side effects due to treatments. For patients who are predicted to have good outcomes, lower intensity therapy can reduce long-term problems from radiation and chemotherapy. For high-risk patients, more intensive therapy can improve chance of survival.

Patients may be offered treatment within a clinical trial.

  1. Surgery to remove as much of the tumor as possible is a main treatment for medulloblastoma. The goal is gross total resection, or complete removal of the tumor. In many cases of medulloblastoma, most or all of the tumor can be removed with surgery. However, in some cases, the location of the tumor may limit how much can be removed safely.

    Posterior Fossa Syndrome after Medulloblastoma Surgery

    Posterior fossa syndrome, or cerebellar mutism, is a rare condition that sometimes develops after surgery to remove a brain tumor in the posterior fossa region of the brain. About 25% of children who have surgery for medulloblastoma will develop posterior fossa syndrome. Symptoms include changes in speech, swallowing, movement, emotions, and behavior. The syndrome develops 1-10 days after tumor surgery, and symptoms can last weeks, months, or longer. Symptoms can be mild or severe, and most children improve over time. The condition is not fully understood, and doctors do not know why it affects some children and not others. Care for posterior fossa syndrome usually includes a combination of rehabilitation services including physical therapy, occupational therapy, and speech therapy.

  2. Radiation therapy is usually used after surgery for medulloblastoma. The dose of radiation therapy depends on the stage of disease and patient risk category. In general, radiation is delivered to the brain and spine (craniospinal irradiation) with a higher dose (boost) at the primary tumor site. Because of the potential health risks, radiation therapy is not used in very young children.

    Doctors may use newer types of radiation therapy such as proton beam radiation to treat medulloblastoma. In this type of radiation therapy, the amount of energy and how deep it goes into the tumor can be tailored to match the tumor size and shape. This allows doctors to aim high doses of radiation at the tumor, reducing damage to nearby healthy cells. However, not every center offers proton therapy.

    Radiation therapy uses beams of radiation, X-rays or protons, to shrink tumors and kill cancer cells. Radiation works by damaging the DNA inside cancer cells.

    Radiation therapy uses beams of radiation, X-rays or protons, to shrink tumors and kill cancer cells. Radiation works by damaging the DNA inside cancer cells.

    Proton therapy uses protons as its energy source. In proton radiation the beam can stop at the tumor site. This allows doctors to aim high doses of radiation at tumors and minimize damage to nearby healthy cells.

    Proton therapy uses protons as its energy source. In proton radiation the beam can stop at the tumor site. This allows doctors to aim high doses of radiation at tumors and minimize damage to nearby healthy cells.

  3. Chemotherapy is usually used along with radiation therapy and surgery to treat medulloblastoma. In very young children, chemotherapy may be used to help delay radiation until the child is older. High-dose chemotherapy with stem cell rescue may also be used.

    A combination of chemotherapy medicines is used to treat medulloblastoma. These medicines often include carboplatin, vincristine, cyclophosphamide, cisplatin, lomustine, and methotrexate.

  4. Targeted therapies work by acting on, or targeting, specific features of tumor cells. These drugs change molecular signals and processes to stop cancer cells from growing, dividing, or communicating. Targeted therapies being studied in medulloblastoma include vismodegib (Erivedge®).

Medulloblastoma in Infants

The SHH subgroup is the most common type of medulloblastoma in children under 3 years of age followed by Group 3 tumors. SHH tumors in infants tend to have a favorable histology and molecular profile. These children often do well with surgery followed by chemotherapy without radiation.

Non-SHH medulloblastoma in infants is harder to treat, especially if there is metastatic disease. Treatments such as focal radiation therapy and high-dose chemotherapy with stem cell rescue may be tried, but the prognosis is usually poor. Young children with high-risk medulloblastoma may experience side effects of treatment that outweigh the possible benefits of treatment.

 

Life After Medulloblastoma

Increased understanding of medulloblastoma has led to improved treatments and better survival rates in recent years. However, medulloblastoma survivors often suffer a variety of treatment-related problems. Ongoing follow-up care, laboratory tests, and routine MRI scans are used to monitor patients after completion of treatment. Monitoring should focus on early detection of recurrence and long-term and late effects of treatment. Care should also include appropriate rehabilitation and neurological consultation.

Late Effects of Medulloblastoma Treatment

Medulloblastoma survivors have an increased risk of certain late effects based on the treatments they received including chemotherapy and radiation therapy. These problems may include:

Children treated for medulloblastoma may have future problems in areas of daily life such as school, work, and relationships. They may also have lower physical fitness and physical function. Regular checkups and screenings by a primary care physician are important to watch for health problems that can develop years after therapy. An interdisciplinary care team can provide a personalized care plan to promote long-term health and quality of life. Support services such as mental health and academic resources can also promote quality of life for survivors.

More: Life After Brain Tumors


Reviewed: February 2020