Astrocytomas are a common type of glioma, which develop from the glial (or supportive) cells in the central nervous system (CNS). More specifically, they develop from a type of glial cell called astrocytes, a star-shaped cell that has a variety of functions, including regulating blood flow and regulating and maintaining synapses. Astrocytomas can develop in any area in the CNS, including the brain and spinal cord. 

The brain is a complex organ that is responsible for controlling all functions of the body. It has five main portions: the cerebrum, cerebellum, brainstem, pituitary gland, and hypothalamus. The cerebrum is the biggest part of the brain, and consists of the frontal, parietal, temporal, and occipital lobes. This part of the brain is responsible for voluntary movement, intelligence, and memory. The cerebellum is a small part of the brain located at the back of the head, and regulates posture and balance. The brainstem is a small, stalk-like structure towards the bottom of the brain that connects the brain to the spinal cord.  It regulates many vital bodily processes, such as swallowing, breathing, and heart rate. The pituitary gland is a pea sized organ located behind the eyes, and is responsible for the production and secretion of hormones in the body. The hypothalamus is located deep within the brain, and has many important functions, such as producing and secreting different hormones, regulating temperature, and controlling appetite. 

The spinal cord is a long, thin, tubular structure that extends down from the brainstem to the lower back. It is made of nerve tissue, and is surrounded by the bones of the spine (vertebrae). The spinal cord is responsible for transmitting nerve signals from the brain to the body, and vice versa. It has motor functions (such as voluntary movement), sensory functions (such as pressure, touch, temperature, and pain), and autonomous functions (such as regulating digestion, heart rate, and blood pressure). 

Astrocytomas are more common in children between the ages of five and eight, and tend to affect the sexes equally. However, anyone can develop this disease.

Types of Astrocytomas 

There are several different types of astrocytomas, which are categorised by how the cells look under the microscope.

Pilocytic Astrocytoma 

Pilocytic astrocytoma, also known as juvenile astrocytoma, is a slow growing subtype of astrocytoma that primarily affects children. It is classified as a grade I tumour, and develops slowly over time. Pilocytic astrocytomas are often found in the cerebrum, cerebellum, optic nerve pathway, or the brain stem. It is generally non-aggressive, and often has a good prognosis. 

Subependymal Giant Cell Astrocytoma 

Subependymal giant cell astrocytomas (SEGAs), also known as intraventricular astrocytomas, are very rare and slow growing subtypes of astrocytomas that primarily affect children and adolescents. They are generally classified as grade I tumours, and often develop in the ventricles of the brain, which are responsible for the production and secretion of cerebral spinal fluid (CSF). While SEGAs are generally not aggressive, they may not have as good of a prognosis as other types of astrocytomas due to the potential obstruction of CSF flow.

Desmoplastic Infantile Astrocytoma (DIA)

Desmoplastic infantile astrocytoma (DIA) is a very rare form of astrocytoma that is generally diagnosed in children under two years old. It is generally classified as a grade I tumour, and is often found in the cerebrum. DIAs are usually slow growing, and can have a good diagnosis when found early.

Diffuse Astrocytoma 

Diffuse astrocytoma is a slow growing subtype of astrocytoma that generally affects young adults. This type of cancer is generally classified as a grade II tumour, is widespread, and has poorly defined borders (diffuse). Diffuse astrocytomas are generally found in the cerebrum, and often grow into nearby structures in the brain. This type of tumour can be non-aggressive, and can have a good prognosis when found early.

Pleomorphic Xanthoastrocytoma

Pleomorphic Xanthoastrocytoma (PXA) is a very rare subtype of astrocytoma that generally affects children and adolescents. Unlike most types of astrocytoma’s, PXA does not affect the sexes equally, and has a prevalence for males. It is generally classified as a grade II tumour, and are often found in the cerebellum. PXAs are usually slow growing, and can have a good prognosis.

Anaplastic Astrocytoma

Anaplastic astrocytoma is a rare subtype of astrocytoma that generally affects adults between the ages of 30 and 50. These cancers are generally classified as grade III tumours, and are often found in the cerebrum. Anaplastic astrocytoma’s are generally aggressive, often metastasise, and may not have as good of a prognosis as other types of astrocytoma. 

Anaplastic Pleomorphic Xanthoastrocytoma 

Anaplastic pleomorphic xanthoastrocytomas (APXAs) are a very rare subtype of astrocytoma that generally affect young adults. Unlike most types of astrocytoma’s, APXA does not affect the sexes equally, and has a prevalence for males. It is generally classified as a grade III tumour, and is often found in the cerebrum. APXA are generally aggressive, and may not have as good of a prognosis as other astrocytomas.

Glioblastoma

Glioblastomas, also known as glioblastoma multiforme (GBM), are a common type of brain tumour that generally affects adults between the ages of 50 and 80. Unlike most types of astrocytomas, GBM does not affect the sexes equally, and has a prevalence for males. Its name is derived from its cellular appearance under the microscope, which is often highly varied. GBM is generally classified as a grade IV brain tumour, and is usually found in the cerebrum. For more information on glioblastomas, please refer to the Rare Cancers Australia Glioblastoma page.

Diffuse Midline Glioma

Diffuse midline gliomas (DMGs) are a rare type of astrocytoma that generally affects children. These tumours often form in the midline structures of the brain, such as the pons in the brainstem, thalamus, spinal cord, and cerebellum. For more information on DMGs, please refer to the Rare Cancers Australia Diffuse Midline Glioma page.

Treatment

When cancers are detected, they are staged and graded based on size, metastasis (whether the cancer has spread to other parts of the body), and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you. However, brain cancers are rarely staged, as they rarely spread to other parts of the body. Instead, they are generally graded from I-IV.

Astrocytomas are generally graded by subtype:

• Grade I (low grade) tumours: cancer cells present as slightly abnormal and are usually slow growing. Includes pilocytic astrocytomas, subependymal giant cell astrocytomas, and DIAs.
• Grade II (intermediate grade) tumours: cancer cells present as abnormal and grow faster than grade-I tumours. Includes diffuse astrocytomas and pleomorphic xanthoastrocytomas.
• Grade III (high grade) tumours: cancer cells present as very abnormal and grow quickly. Includes anaplastic astrocytomas and anaplastic pleomorphic xanthoastrocytomas.
• Grade IV (high grade) tumour: cancer cells present as very abnormal and grow very quickly. Grade IV tumours are more aggressive than grade III tumours. Includes glioblastoma and diffuse midline glioma.

Once your tumour has been graded, your doctor may recommend genetic testing, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you. 

Treatment is dependent on several factors, including location, age, stage of disease and overall health.

Treatment options for astrocytomas may include:

• Surgery to remove the tumour.
• Watch and wait.
• Radiation therapy, potentially including:
  • Conformal radiation therapy.
  • Intensity-modulated radiation therapy (IMRT).
  • Stereotactic radiation therapy.
  • Proton beam radiation therapy.
• Chemotherapy. 
• Stem cell transplant. 
• Targeted therapy, potentially including:
  • Monoclonal antibodies.
  • Protein kinase inhibitors.
• Immunotherapy, potentially including immune checkpoint inhibitor therapy.
• Clinical trials.
• Palliative care. 

For more information on the treatment options, please refer to the Rare Cancers Australia treatment options page. 

Risk factors

Although it is a relatively common type of brain tumour, it is not clear what the risk factors for astrocytomas are. However, researchers have identified a potential link to certain genetic changes in DNA. 

Early symptoms

Astrocytomas may appear asymptomatic in the early stages of disease. As the cancer progresses, some of the following symptoms may appear:

• Headaches (commonly in the morning, and may go away after vomiting). 
• Nausea and/or vomiting.
• Difficulties with vision, hearing, and/or speaking. 
• Loss of balance.
• Difficulties walking.
• Fainting.
• Worsening handwriting and speaking skills. 
• Weakness or changes in one side of the body.
• Fatigue.
• Changes in energy levels.
• Changes in personality and behaviour.
• Seizures.
• Unexplained weight loss or weight gain.
• Unusual increase in head size (in infants).  

Not everyone with the symptoms above will have cancer but see your general practitioner (GP) if you are concerned.

Some of the information regarding symptoms was obtained from the Childhood Glioma (including Astrocytoma) page published by the National Cancer Institute. 

Diagnosis/diagnosing

If your doctor suspects you have an astrocytoma, they may order the following tests to confirm the diagnosis and refer you to a specialist for treatment.

Physical examination

Your doctor will collect your overall medical history, as well as your current symptoms. Following this, they may examine your body to check for any abnormalities.

Neurological examination

A neurological examination assesses sensory and motor functions, and can generally be done in your GPs office. The doctor may check your vision, hearing, balance, coordination, strength and reflexes, depending on the signs and symptoms you have described. Any problem that is detected in this exam can help determine which portion of the CNS needs further investigation.

Imaging & blood tests

The doctor will take images of your body using magnetic resonance imaging (MRI), a computed tomography scan (CT scan), x-rays, bone scan and/or positron emission tomography (PET scan), depending on where it is suspected the cancer is. The doctor may also look at other parts of the body and looks for signs of metastasis. Additionally, a blood test may be taken to assess your overall health and help guide treatment decisions.

Biopsy

Once the location of the cancer has been identified, the doctor will perform a biopsy to remove a section of tissue using a needle. This may be done during a surgery, or by a stereotactic needle biopsy.

Prognosis (Certain factors affect the prognosis and treatment options)

While it is not possible to predict the exact course of the disease, your doctor may be able to give you a general idea based on the rate and depth of tumour growth, susceptibility to treatment, age, overall fitness, and medical history. Generally, low-grade astrocytomas have a better prognosis and survival rates. However, if the cancer is advanced and has spread, the prognosis may not be as good and there may be a higher risk of cancer recurrence. It is very important to discuss your individual circumstances with your doctor to better understand your prognosis.

References

• Cancer Research UK
• Mayo Clinic
• National Cancer Institute
• National Organisation for Rare Diseases (NORD)

^{Some references are to overseas websites. There may be references to drugs and clinical trials that are not available here in Australia.}