Oligodendrogliomas 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 oligodendrocytes, which produce a fatty, white substance known as myelin. Myelin is a protective sheath for nerves, and assists with the quick and efficient transmission of electrical impulses (or signals) in the body. Oligodendrogliomas can develop in any area of the CNS, but are most commonly found in the frontal and temporal lobes of the cerebrum.
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).
Oligodendrogliomas are more common in males, and are generally diagnosed in people between the ages of 20-40. However, anyone can develop this disease.
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 only graded.
The grades of oligodendrogliomas include:
- Grade II (low grade) tumours: cancer cells present as slightly abnormal and are usually slow growing.
- Grade III (high grade) tumours: cancer cells present as very abnormal and often develop quickly. Grade III oligodendrogliomas are also known as anaplastic oligodendrogliomas.
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 oligodendrogliomas may include:
- Surgery to remove as much as the tumour as possible.
- Watch and wait (only for low-grade tumours).
- Radiation therapy.
- Chemotherapy, potentially including PCV which is a combination of the following medications:
- Procarbazine.
- Lomustine (CCNU).
- Vincristine.
- 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 oligodendrogliomas are. However, previous exposure to radiation and certain genetic mutations that can be inherited has been linked to this disease.
Early symptoms
The symptoms of an oligodendroglioma often depend on the grade of the tumour, as well as its location within the brain. Low-grade oligodendrogliomas may appear asymptomatic in early stages, causing a delay in diagnosis. As the tumour progresses, some of the following symptoms may appear:
- Seizures.
- Persistent headaches.
- Difficulties with concentration, thinking and/or learning.
- Changes regarding problem-solving and/or decision making.
- Personality changes.
- Persistent weakness and/or numbness, most commonly in the arms or legs.
- Difficulties with balance and/or movement.
Not everyone with the symptoms above will have cancer, but see your general practitioner (GP) if you are concerned.
Diagnosis/diagnosing
If your doctor suspects you have an oligodendroglioma, 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 oligodendrogliomas 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
Some references are to overseas websites. There may be references to drugs and clinical trials that are not available here in Australia.