What is a cerebellar pilocytic astrocytoma?
(grade I pilocytic astrocytoma of the cerebellum)
(grade II fibrillary astrocytoma of the cerebellum)
A cerebellar low-grade glioma is a tumor arising from a type of cell of the central nervous system known as a glial cell. These tumors originate from a specific type of glial cell known as an astrocyte. Astrocytes make up the supportive network of the brain. These cells are named for their star-like appearance.
As you read further below, you will find general information about cerebellar low-grade glioma. If you would like to view summary information about brain tumors first, see the overview on brain tumors.
Cerebellar low-grade gliomas are astrocytomas that arise in the location of the brain known as the cerebellum. The cerebellum is the center of the brain that controls balance and coordination. Of patients with cerebellar low-grade gliomas, 80-85 percent have what is called grade I pilocytic astrocytomas, and the remaining 15-20 percent have what is called grade II fibrillary astrocytomas. These cerebellar astrocytomas account for 10-20 percent of all childhood brain tumors. They tend to occur before the age of 10 years, most commonly between the ages of 6 and 9.
What causes cerebellar low-grade gliomas?
Children with certain genetic syndromes, including neurofibromatosis type I and tuberous sclerosis, are at higher risk of developing tumors of glial origin, including cerebellar low-grade gliomas. The vast majority of children with cerebellar low-grade gliomas however, develop these tumors spontaneously, meaning there is no identifiable cause.
What are the symptoms of a cerebellar low-grade glioma?
Due to the relative slow growth rate of cerebellar low-grade gliomas, children with these tumors tend to present to the doctor with symptoms that have been occurring for many months. Some children, however, have a more sudden onset of symptoms. The following are the most common symptoms of a cerebellar low-grade glioma, however, each child may experience symptoms differently. Common symptoms may include:
Oh more that 90 percent of patients present with symptoms of increased pressure within the brain. These symptoms include:
*headache (generally upon awakening in the morning)
*Oh the majority of children have evidence of difficulty with balance and coordination
The symptoms of a brain tumor may resemble other conditions or medical problems. Always consult your child's physician for a diagnosis.
How is a cerebellar low-grade glioma diagnosed?
Diagnostic procedures for a cerebellar low-grade glioma may include:
*physical examination - the child may demonstrate difficulty walking and coordinating movements of the hands and/or legs
*computerized tomography scan (also called a CT or CAT scan) - a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. CT scans are more detailed than general x-rays. For cerebellar low-grade gliomas, a CT scan of the brain is usually done.
*magnetic resonance imaging (MRI) - a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body. For cerebellar low-grade gliomas, an MRI of the brain is usually done. In rare cases when cerebellar low-grade gliomas spread to the spine, an MRI of the spine may also be ordered.
*biopsy - in many cases, a tissue sample from the tumor will be taken through a needle during a simple surgical procedure performed by a surgeon to confirm the diagnosis
What are the treatments for a cerebellar low-grade glioma?
Specific treatment for a cerebellar low-grade glioma will be determined by your child's physician based on:
*your child's age, overall health, and medical history
*type, location, and size of the tumor
*extent of the disease
*your child's tolerance for specific medications, procedures, or therapies
*how your child's doctors expects the disease to progress
*your opinion or preference
Treatment may include (alone or in combination):
*surgery - the initial treatment is surgery, and complete tumor removal is associated with a very high rate of cure. In cases when the tumor recurs after initial surgical removal, or if the tumor re-grows after partial surgical removal, the recommended treatment would be a second attempt at surgical removal/de-bulking of the tumor.
*radiation and chemotherapy - in cases of residual/recurrent disease, where maximal surgical removal has been achieved, alternative treatment options include chemotherapy and radiation therapy:
*chemotherapy - a drug treatment that works by interfering with the cancer cell's ability to grow or reproduce. Different groups of chemotherapy drugs work in different ways to fight cancer cells and shrink tumors. Often, a combination of chemotherapy drugs is used to fight a specific cancer. Certain chemotherapy drugs may be given in a specific order depending on the type of cancer it is being used to treat.A number of combinations of chemotherapy drugs are being tested to treat cerebellar low-grade gliomas, including vincristine with carboplatin, and vincristine with CCNU, procarbazine and thioguanine. While chemotherapy can be quite effective in treating certain cancers, the agents do not differentiate normal healthy cells from cancer cells. Because of this, there can be many adverse side effects during treatment. Being able to anticipate these side effects can help the care team, parents, and child prepare, and, in some cases, prevent these symptoms from occurring, if possible. Chemotherapy is systemic treatment, meaning it is introduced to the bloodstream and travels throughout the body to kill cancer cells.
Chemotherapy can be given:
*as a pill to swallow
*as an injection into the muscle or fat tissue
*intravenously (directly to the bloodstream; also called IV)
*intrathecally - chemotherapy given directly into the spinal column with a needle
*radiation therapy - using high-energy rays (radiation) from a specialized machine to damage or *kill cancer cells and shrink tumors. Radiation therapy to the tumor bed is also being used for recurrent disease.
The effectiveness of these methods of treatment is still being studied. There is some evidence to suggest that the use of chemotherapy and/or radiation therapy may increase long-term survival in children with incompletely removal tumors.
How are side effects of treatment managed?
Children with cerebellar low-grade gliomas may have side effects related to the tumor itself and its treatment. Symptoms at the time of diagnosis related to increased pressure within the brain, such as headache, vomiting and lethargy, are often relieved by surgical removal of the tumor. Effects on coordination and balance are also often improved with surgical removal of the tumor that is compressing structures that control these functions. Dexamethasone, an oral steroid, is often used, especially in the post-operative period, to assist in controlling these systems as well as any additional tissue swelling that may occur post-operatively.
Common side effects related to chemotherapy include nausea, vomiting and decreased blood counts (i.e. anemia). Anti-emetics (anti-nausea) medications are administered with the chemotherapy to control symptoms of nausea and vomiting. Occasionally, children receiving chemotherapy will require transfusion of red blood cells and/or platelets to replace these cells, since chemotherapy temporarily decreases the body's ability to produce red blood cells and platelets. White blood cells are reduced with chemotherapy, however these cells are not transfused. Occasionally, children will receive a medication to assist the body in producing white blood cells. Radiation therapy may cause swelling related to tissue inflammation. This inflammation may lead to symptoms of headache or difficulty with coordination. These symptoms, if significant, may be treated with the oral medication dexamethasone.
What is the expected outcome after treatment for cerebellar low-grade glioma?
Grade I cerebellar gliomas are associated with a 10-year survival rate of 70-100 percent after surgical removal alone. Grade II cerebellar gliomas are more likely to recur after surgical removal. Recurrent disease may necessitate the use of chemotherapy and/or radiation therapy. Inability to achieve a complete surgical removal and the presence of recurrent disease decreases prognosis and long-term survival.
What about progressive or recurrent disease?
The recommended treatment for progressive or recurrent cerebellar low-grade glioma is reattempt at surgical removal. In cases of progressive/recurrent disease, where maximal surgical removal has been achieved, chemotherapy and/or radiation therapy will be recommended. The Dana-Farber Cancer Institute is one of nine institutes in the nation belonging to the Pediatric Brain Tumor Consortium. The consortium is dedicated to the development of new and innovative treatments for children with progressive/recurrent brain tumors not responsive to standard therapies. Children with progressive/recurrent low-grade glioma of the cerebellum would be eligible for a number of experimental therapies available through the consortium.
Friday, December 12, 2008
What is a cerebellar pilocytic astrocytoma?