Astrocytomas are tumors that arise from astrocytes—star-shaped cells that make up the “glue-like” or supportive tissue of the brain. Many astrocytomas are slow growing and tend to invade surrounding tissues. These tumors are called “diffuse” because it is difficult to tell where the tumor begins and ends. Other kinds of astrocytomas (e.g., pilocytic astrocytoma) are more circumscribed, meaning that there is a sharper border between the tumor and surrounding brain.
Diffuse astrocytomas are classified into adult-type and pediatric-type tumors. Astrocytomas may be either IDH-mutant or non-mutant (a.k.a. wildtype). IDH-mutant astrocytoma is divided into three grades (2, 3, or 4) with higher grades associated with more rapid growth and recurrence. IDH-wildtype diffuse astrocytomas may be classified as glioblastoma if they have other microscopic and genetic features of glioblastoma Circumscribed astrocytomas are also IDH-wildtype, although they tend to be less aggressive than either IDH-wildtype or IDH-mutant diffuse astrocytomas.
Location
Astrocytomas can appear in various parts of the brain and nervous system, including the cerebellum, cerebrum, brainstem, spinal cord, and central areas of the brain. They most commonly develop in the frontal or temporal lobes.
Symptoms
Common signs of an astrocytoma are seizures, headaches, and personality changes. Other symptoms may include weakness or numbness in an arm or leg, or changes related to thinking, learning, concentrating, problem-solving, and decision-making. Symptoms will vary by location and size of the tumor.
Treatment
If the tumor is located in a surgically accessible part of the brain, the usual treatment for astrocytomas is removal of as much of the tumor as possible. Depending on the kind of astrocytoma, surgery may be the only treatment that is needed. If a tumor is in a location that is unsafe for surgical removal, biopsy is usually done to confirm the diagnosis and help guide treatment.
If some of the tumor remains (also called “residual” tumor), or if the tumor has molecular characteristics that suggest it may be more likely to recur, radiation therapy may be recommended following surgery. Radiation therapy generally takes place over the course of a six-week time period and may be given along with chemotherapy.
Depending upon the amount of tumor that is not able to be removed (residual tumor) and the molecular characteristics of the tumor itself, chemotherapy or targeted therapy may be suggested to treat the remaining tumor. Chemotherapy may be administered via a pill or an intravenous injection. Vorasidinib, a targeted therapy, was recently approved by the FDA to treat grade 2 astrocytomas with IDH mutations. This medication, taken once daily, has been shown to slow tumor regrowth.
Regular MRI scans are recommended following the diagnosis of astrocytoma, generally at least once per year. Patients with seizures will need to be followed for their seizure medication.
A recurring astrocytoma may be treated with surgery, particularly when the time between initial diagnosis and recurrence is extended. In this way, the diagnosis can be updated to reflect any molecular changes in the tumor that may have occurred over time as the tumor adapts to treatments. Recurrent astrocytomas may also be treated with radiation therapy, depending on whether or how much radiation was given after the original diagnosis. Chemotherapy/immunotherapy and clinical trials are additional options.
Prognosis
Prognosis means a prediction of outcome. This information is usually based on information gathered from groups of people with the same disease. It is important to remember these statistics are not individualized.
The proportion of patients by age group who are still alive 5 years after a diagnosis of diffuse astrocytoma are as follows:
- Children (ages 0-14): 82.4%
- Adolescents and Young Adults (ages 15-39): 78.2%
- Adults (ages 40+): 34.0%
Incidence
Adult astrocytomas are estimated to account for 3.5% of all primary brain tumors with approximately 1,500 new diagnoses in the United States each year.
Age Distribution
Diffuse astrocytomas most often occur between the ages of 20-60 with a median age at diagnosis of 46 years for lower grade lesions and 54 years for higher grade lesions.
Although these tumors are found in both men and women, they tend to occur more often in men.
Risk Factors
Molecular Profile
Molecular profiling is the detection of specific genes, proteins, or other molecules in a tumor. This information helps confirm tumor diagnosis, inform treatment options, and predict prognosis.
Among adult-type diffuse astrocytomas, IDH-mutant astrocytomas are a type of glioma that have mutations in either IDH1 or, less commonly, IDH2. Other genes, like ATRX and TP53, are often mutated alongside IDH1 or IDH2. If a gene called CDKN2A/B is completely lost, the IDH mutant astrocytoma is automatically grade 4 regardless of what it looks like under the microscope. If an IDH-wildtype astrocytoma has other genetic changes in genes like TERT and EGFR, as well as gain of chromosome 7 and loss of chromosome 10, the tumor is automatically a glioblastoma, IDH-wildtype, grade 4. The genetics of circumscribed astrocytomas are more complicated and can be discussed with your physician.
Additional Resources
Content last reviewed:
December 2024 by Elizabeth Claus, MD, PhD and Craig Horbinski MD, PhD
