Malignant Astrocytoma
Malignant astrocytomas are aggressive brain cancers that grow from star-shaped support cells in the brain and spinal cord. These tumors grow quickly, spread into nearby brain tissue, and require intensive treatment including surgery, radiation, and chemotherapy.
Table of contents
- What is a malignant astrocytoma?
- Types and grades
- How common are they?
- Signs and symptoms
- Causes and risk factors
- How they are diagnosed
- Treatment options
- Survival and outlook
What is a malignant astrocytoma?
Malignant astrocytomas are brain tumors that begin in cells called astrocytes, which are star-shaped support cells in the brain and spinal cord[1]. These cells normally help and support nerve cells, but when they grow out of control, they form tumors[2].
Most astrocytomas grow quickly and are considered brain cancers. Unlike some brain tumors that have clear borders, malignant astrocytomas spread into surrounding brain tissue, making them difficult to remove completely[3]. This spreading nature means there is no clear separation between the tumor and normal brain tissue[13].
Astrocytomas belong to a larger group of tumors called gliomas, which develop from glial cells (the supportive tissue in the brain)[2]. Astrocytoma is the most common type of glioma, accounting for about 60% of all brain tumors[7].
Types and grades
Healthcare providers use a grading system to describe how aggressive an astrocytoma is. The World Health Organization classifies astrocytomas from grade 1 (most benign) to grade 4 (most malignant)[3]. The grade depends on how abnormal the cells look under a microscope and how fast they grow[13].
Malignant astrocytomas include:
- Grade 2 astrocytomas (Diffuse astrocytoma): These tumors tend to spread to nearby brain tissue. The cells look abnormal under a microscope and are more numerous than normal. Surgery alone might not be enough to treat them[3].
- Grade 3 astrocytomas (Anaplastic astrocytoma): These are more aggressive than grade 2 tumors and often develop as a progression from lower-grade astrocytomas. They grow faster and show more abnormal cells under examination. Surgery alone never cures these tumors, and they require radiation and almost always chemotherapy[2][3].
- Grade 4 astrocytomas (Glioblastoma): These are the most malignant and aggressive form of astrocytoma. They grow and spread rapidly through the brain. The cells appear very abnormal, create new blood vessels, and cause areas of dead tissue[3]. Glioblastoma can either develop from a previously existing lower-grade astrocytoma (10% of cases) or begin directly as a grade 4 tumor (90% of cases)[2][13].
Doctors also look for genetic changes in the tumor cells, particularly mutations in the IDH gene. Tumors with these mutations are called IDH-mutant astrocytomas, while those without are called IDH-wildtype[6].
How common are they?
Different grades of malignant astrocytoma occur at different frequencies:
- Grade 2 astrocytomas account for 2% to 5% of all brain tumors[2]
- Grade 3 astrocytomas account for 4% of all brain tumors[2]
- Grade 4 astrocytomas (glioblastomas) account for 24% of all brain tumors and are the most common type of brain cancer in adults[2]
In the United States, about 15,000 new astrocytomas are diagnosed every year. Males are slightly more affected than females, with a ratio of 1.3 to 1[3].
Different grades tend to affect people at different ages. Grade 2 astrocytomas most often affect adults between 20 and 60 years old. Grade 3 astrocytomas typically affect adults between 30 and 60, while glioblastoma (grade 4) most commonly occurs in adults between 50 and 80 years old[2][3].
Signs and symptoms
Astrocytoma symptoms vary based on where the tumor is located in the brain or spinal cord[1].
When astrocytomas occur in the brain, symptoms may include:
- Seizures, which might cause loss of consciousness or changes in behavior[1]
- Headaches[1]
- Nausea and vomiting[1]
- Personality changes[1]
- Problems speaking[1]
- Feeling very tired or weak[1]
When astrocytomas occur in the spinal cord, symptoms may include:
- Pain in the affected area[1]
- Weakness and disability in the area affected by the growing tumor[1]
- Numbness in an arm or leg[2]
If a tumor is growing in an area where there is room to expand, it might not cause symptoms until it becomes larger. Cancerous tumors may cause symptoms earlier than noncancerous tumors because they grow more quickly[10].
Causes and risk factors
The exact cause of most astrocytomas is unknown. Most astrocytomas develop randomly without a clear underlying cause[2][7].
The only well-established risk factor is exposure to ionizing radiation[7]. Children who receive radiation therapy to the head for other conditions, such as acute lymphocytic leukemia, may have a 22 times higher risk of developing a brain tumor within about 5 to 10 years[7]. Radiation therapy for pituitary adenoma carries 16 times more risk of glioma development[7].
Some genetic conditions may increase the risk of developing an astrocytoma, including:
However, only a minority of patients have a family history or genetic condition associated with astrocytoma[7].
There is no proven association between astrocytomas and other factors such as exposure to electromagnetic fields (including cellular telephones), head injury, or occupational risk factors[7].
How they are diagnosed
Several tests and procedures are used to diagnose astrocytoma:
Neurological examination: During this exam, a healthcare provider will ask about symptoms and check vision, hearing, balance, coordination, strength, and reflexes. Problems in these areas can help identify which part of the brain is affected by the tumor[12].
Imaging tests: These tests help determine the location and size of the brain tumor. MRI (magnetic resonance imaging) is most often used to diagnose brain tumors. It may be combined with specialized MRI techniques such as functional MRI, perfusion MRI, and magnetic resonance spectroscopy. Other imaging tests may include CT scans (computed tomography) and PET scans (positron emission tomography)[12].
Biopsy: This procedure removes a sample of tissue from the tumor for testing. Often the sample is taken during surgery to remove the astrocytoma. If the tumor is in a hard-to-reach location, a needle might be used to obtain the sample[12].
The tissue sample is examined in a laboratory to determine the types of cells and how quickly they grow. Special tests look for changes in the genetic material of the tumor cells. These tests might look for mutations in genes such as IDH (isocitrate dehydrogenase)[6]. The results help the healthcare team understand the prognosis and create a treatment plan[12].
Treatment options
Treatment for malignant astrocytomas typically involves multiple approaches. Treatment decisions are best made through a team approach, including input from neurosurgeons, radiation oncologists, medical oncologists, and the patient and their family[14].
Surgery: Surgical removal is the main treatment for astrocytomas. The goals of surgery are to remove as much of the tumor as possible while avoiding further damage to the brain. A brain surgeon (neurosurgeon) works to remove the astrocytoma, but complete removal is often impossible because these tumors spread into surrounding brain tissue[3][12].
Studies show that larger extent of removal is associated with improved survival. However, the boundaries of these tumors extend far beyond what can be seen on imaging studies[14]. Several methods can be used during surgery to map functional areas of the brain, such as those controlling speech, language, and motor functions, to ensure safe removal while avoiding important brain structures[14].
Radiation therapy: This treatment uses high-energy rays to destroy cancer cells. Radiation therapy is often recommended after surgery for malignant astrocytomas[6][12].
Chemotherapy: This treatment uses drugs to kill cancer cells. Chemotherapy is frequently used for malignant astrocytomas, particularly grade 3 and grade 4 tumors[2][3].
For grade 2 astrocytomas, surgery is the main treatment. Radiation therapy might be recommended after surgery if the patient is over 40 years old or if a significant amount of tumor remains after surgery[6].
For grade 3 astrocytomas, surgery alone is never considered curative. These tumors require radiation therapy and almost always require chemotherapy[2][3].
For grade 4 astrocytomas (glioblastoma), treatment typically involves surgery followed by radiation and chemotherapy[3].
Survival and outlook
The prognosis for malignant astrocytoma depends on the grade of the tumor. Higher-grade tumors generally have poorer outcomes than lower-grade tumors.
For high-grade astrocytomas (grades 3 and 4), the mean overall survival is 31.9 months. Two-year survival is 38.1%, and five-year survival is 28.6%[27].
For low-grade astrocytomas (grade 2), the mean overall survival is 64.8 months. Two-year survival is 74.3%, and five-year survival is 74.4%[27].
Glioblastoma (grade 4) is the most aggressive form. When it presents as a progression from a lower-grade tumor, this typically occurs in younger patients, while tumors that begin as grade 4 are most common after age 60. Regardless of presentation, glioblastoma is the most malignant and common form of astrocytoma, accounting for 60% of all astrocytomas[3][13].
Several factors influence survival, including the patient’s age, the extent of surgical removal, and the tumor’s genetic characteristics. Generally, with the exception of grade 1 tumors, most astrocytomas affect patients older than 40, and the older the patient, the higher the likelihood that the astrocytoma will be of a higher grade[3].
- Brain
- Spinal cord
- Cerebrum
- Cerebellum
- Brain stem
- Temporal lobe
- Frontal lobe
- Ventricles
