What is an Astrocytoma/Glioma?
Astrocytoma, also called glioma, is the most common brain tumor, accounting for more than half of all Central Nervous System (CNS) malignancies. These tumors originate from astrocytes, which are star-shaped brain cells. Astrocytes are a type of glial cell which function to support the surrounding cells. Astrocytomas typically occur in the first decade of life with the peak age of occurrence between 5 and 9 years.
Astrocytomas are categorized by their microscopic appearance, as defined by the World Health Organization (WHO) Classification System. The WHO grading system divides astrocytomas into four subsets based on its growth potential and extent of invasiveness;
Grade I and II Astrocytomas are slow growing tumors, usually termed “low grade gliomas.”
Grade III and IV Astrocytomas are fast growing tumors, usually termed “high grade gliomas.”
Grade I Astrocytomas (which include pilocytic astrocytomas, subependymal giant cell astrocytomas, angiocentric glioma, and subependymomas) are the most common astrocytoma seen in childhood. These tumors are commonly located in the cerebellum, cerebral hemisphere, brainstem, spinal cord, hypothalamus, and the optic tracts. Grade I astrocytomas tend to be well contained and do not spread into the surrounding brain. Typically Grade I astrocytomas can be completely removed surgically. The exception is an optic pathway astrocytoma, which is a juvenile pilocytic astrocytoma that has moved into the areas of the brain contributing to vision.
Grade II Astrocytomas are infiltrative tumors, where the cells penetrate into the surrounding normal brain, making complete surgical resection more difficult. Grade II gliomas include fibrillary astrocytoma, gemistocytic astrocytoma, protoplasmic astrocytoma, pilomyxoid astrocytomas, pleomorphic xanthoastrocytomas and desmoplastic infantile astrocytoma. Grade II astrocytoma are mainly located in the cerebral hemispheres.
Grade III Astrocytoma (anaplastic astrocytoma) and Grade IV Astrocytoma (glioblastoma multiforme) are highly malignant, fast growing tumors deep among the white matter tracts of the brain. High-grade gliomas are usually found in the cerebral hemispheres or the brainstem.
For the majority of astrocytoma, the cause is unknown. Children with a family history of cancer have an increased risk for developing both low grade and high-grade gliomas. Children with Neurofibromatosis Type I have an increased risk of developing astrocytomas, with low grade astrocytoma being the most common subtype and the optic pathway, hypothalamus and brainstem being the most common locations. The only known environmental cause for astrocytoma is previous exposure to ionizing radiation.
What are the symptoms of an Astrocytoma/Glioma?
Symptoms vary depending on:
- tumor location within the central nervous system
- aggressiveness or grade of the tumor
- age of the patient
Tumors can cause non-specific symptoms due to pressure on the brain resulting in increased intracranial pressure (ICP). Symptoms due to ICP may include headaches, vomiting, subtle developmental delay, lethargy, poor balance, incontinence of urine and behavioral changes. Infants tend to have more subtle symptoms because their skull bones have not fused together, therefore the skull can expand to make room for the growing tumor. Infants with a brain tumor may have an enlared head and symptoms such as irritability, vomiting, failure to thrive, and regression of developmental milestones. Tumors may result in symptoms caused by pressure on the nearby brain or spinal cord. These focal symptoms can help pinpoint the tumor location and may include seizures, weakness, or impairment in speech, memory or vision. Spinal cord tumors frequently cause back pain, weakness, loss of sensation and bladder or bowel dysfunction.
How is an Astrocytoma/Glioma diagnosed?
A MRI of the brain and spine is done to further define the location of the tumor and to assess if there is any metastasis (spread) of the tumor. Patients who experience seizures also undergo an EEG to locate where the seizure originated in the brain. Patients with optic pathway gliomas undergo a thorough ophthalmology (eye). Patients who have tumors located in the cerebral hemispheres may undergo functional studies (functional MRI or magnetoencephalogram) to map out the important brain function located around the tumor, which helps the surgeon avoid important functional areas of the brain at the time of surgical removal of the tumor. A biopsy of the tumor is required to make the final diagnosis of an astrocytoma/glioma and to subtype it according to WHO guidelines.
How is an Astrocytoma/Glioma treated?
The treatment of astrocytoma depends on the size and location of the tumor, its type and grade, whether the tumor has spread, and the child’s overall health. Typically, three types of treatments are used to treat children with astrocytoma: surgery, radiation therapy, and chemotherapy.
Surgery is the most important treatment for astrocytomas. The goal of surgery is to get a piece of the tumor to make a histological diagnosis and to remove as much of the tumor as possible without causing significant neurological injury. All grades of astrocytoma have the best outcome following complete removal of the tumor. Most, though not all, astrocytomas/gliomas can be treated surgically.
Chemotherapy is effective for low-grade astrocytomas that are inoperable because of location (optic pathway and hypothalamus) or have shown early recurrence or growth of disease. Chemotherapy is usually preferred over radiation therapy in prepubertal children to avoid the potential long-term side effects of radiation. Chemotherapy, combined with surgery and radiation, is considered standard treatment for most high-grade glioma.
Radiation is very effective for the treatment of low-grade gliomas. However, because of its potential long-term toxicities including cognitive impairment, secondary malignancies, and vascular injury, it is usually recommended for older children or younger children who have recurrence of disease following chemotherapy. Radiation is part of the standard treatment for high-grade gliomas and is essential to improving the outcome for this diagnosis.
Surgical resection is the preferred treatment and if possible, complete surgical removal is the goal in order to minimize the risk of local recurrence. However, long-term control of low grade gliomas may occur even after partial resection; therefore many patients can be observed and monitored without further treatment after partial resection if there is little risk of neurologic impairment from further growth of the tumor. Low-grade tumors that progress or recur after surgery often can be cured by surgical resection depending on the location of the recurrent tumor.
Chemotherapy or radiation therapy may be used to treat low-grade tumors that are inoperable (such as optic tract, hypothalamic and thalamic tumors), partially resected and have a high risk of neurologic impairment if allowed to regrow, or demonstrate early progression. Chemotherapy is usually preferred in young children to avoid or to delay radiation, and its potential neurologic toxicities. There are several different effective chemotherapy regimens for low-grade astrocytomas. Radiation therapy is usually reserved for older children or for children who have not had good results from chemotherapy.
Surgical resection is the recommended treatment and if feasible, complete surgical removal is the goal in order to minimize the risk of local recurrence. Following surgical resection, treatment with local radiation and chemotherapy occurs. Chemotherapy has been found to improve outcome in high-grade astrocytomas, however these tumors are fairly resistant to chemotherapy. Current clinical trials are testing new chemotherapy and biological agents in high-grade gliomas with the hope of improving the outcomes.
About treatment for Astrocytoma/Glioma at Children’s Hospitals and Clinics of Minnesota
Our cancer and blood disorders program consistently achieves excellent results ranking it in the top ten programs in the United States. Children’s Hospitals and Clinics of Minnesota treats the majority of children with cancer and blood disorders in Minnesota and provides patients access to a variety of clinical trials using ground-breaking new treatments. Through our renowned program, patients experience unparalleled family support, a nationally recognized pain management team, and compassionate, coordinated care.
If you are a family member looking for a Children’s neuro-oncologist, please call our clinic at (612) 813-5940.
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