Other names for Oligodendroglioma include: Anaplastic oligodendroglioma, IDH-mutant oligodendroglioma, Oligoastrocytoma
What is oligodendroglioma?
Oligodendroglioma is a type of brain tumor known as a glioma. Oligodendroglioma gets its name because the tumor cells look like oligodendrocytes, cells that form a protective cover for nerves in the brain.
Oligodendrogliomas most often develop in the white matter of the cerebrum. About half occur in the frontal lobe.
Most oligodendrogliomas occur in adults. They are very rare in children and teens. Less than 1% of brain tumors in children under 14 years of age are oligodendrogliomas.
Oligodendrogliomas can be low grade (grade II) or high grade (grade III). These tumors are often diffuse and may not have well-defined borders. Treatment usually includes surgery to remove as much of the tumor as possible. Radiation therapy is often used to kill remaining cancer cells. Chemotherapy may also be used. Survival rates for children with oligodendroglioma depend on the tumor grade and success of surgery. Patients with low-grade tumors that are completely removed by surgery have a survival rate greater than 90%.
Symptoms of oligodendroglioma
Oligodendrogliomas are often slow growing. The tumor may be present for years before it causes problems. Signs and symptoms of oligodendroglioma depend on several factors including child’s age, tumor size, location of the tumor, and how fast it grows.
Oligodendroglioma symptoms may include:
Seizures (most common)
Changes in personality or behavior
Weakness or numbness on one side of the body
About half of patients experience seizures before diagnosis. Most patients (about 80%) will have seizures at some point during the course of their illness.
Diagnosis of oligodendroglioma
Doctors test for oligodendroglioma in several ways.
A physical exam and medical history help doctors learn about symptoms, general health, past illness, and risk factors.
Risk Factors: The cause of oligodendroglioma is unknown, but certain genetic changes in cells are associated with these tumors. Oligodendrogliomas usually occur in adults and are more common in males. Pediatric oligodendrogliomas are most often seen in teens and young adults.
A neurological exam measures different aspects of brain function including memory, vision, hearing, muscle strength, balance, coordination, and reflexes.
An electroencephalogram (EEG), measures electrical activity of the brain. This test monitors and records seizure activity through scalp electrodes.
Imaging tests are used to help identify the tumor, see how big the tumor is, and find out what brain areas may be affected. Oligodendrogliomas often contain areas of calcium deposits (calcification) within the tumor. These calcium deposits can be seen on certain imaging tests and can help make the diagnosis. Magnetic resonance imaging (MRI) is the main imaging technique that is usually used to evaluate oligodendroglioma. The images made by MRI can give more information about the type of tumor and the potential spread of disease. An MRI is also done after surgery to see if any tumor remains.
A biopsy is usually used to diagnose oligodendroglioma. In a biopsy, a small sample of the tumor is removed during surgery. A pathologist looks at the tissue sample under a microscope to identify the specific grade of tumor. The tissue is also examined for molecular features and genetic markers that give more information about the tumor.
Staging and grading of oligodendroglioma
Oligodendroglioma tumors are grouped by how they look under the microscope. The more abnormal the cells look, the higher the grade. Oligodendrogliomas are usually grade II or III.
Grade II oligodendroglioma is considered low grade. The cells look more like normal cells and grow more slowly. They are less likely to spread to other parts of the brain.
Grade III oligodendroglioma is considered high grade. These tumors are called anaplastic oligodendrogliomas. They are more aggressive and can spread more easily.
In the past, a diagnosis of oligodendroglioma was based mainly on how the tumor cells looked under a microscope. However, doctors are learning more about specific molecular changes and gene mutations (DNA changes) that occur in the cells of the tumor. Most oligodendrogliomas have a specific molecular marker that help in the diagnosis. First is a gene mutation known as an IDH-mutation, which may be seen in different types of gliomas. Oligodendrogliomas are identified based on an IDH1 or IDH2 mutation. Usually, oligodendrogliomas also have a change in chromosomes called a 1p/19q codeletion. However, pediatric oligodendrogliomas, especially in younger children, may not have these molecular features. In these cases, doctors rely on imaging tests, pathology, and clinical features to make a diagnosis. Understanding the specific changes in tumor cells can help doctors plan treatments and develop better therapies in the future.
Prognosis for oligodendroglioma
Oligodendroglioma is much more common in adults, and less is known about the prognosis for pediatric patients. Overall, children tend to have better outcomes compared to adults. For pediatric oligodendroglioma, the overall 5-year survival rate is greater than 80%. However, treatment outcomes can vary widely based on the success of surgery, age at diagnosis, molecular features of the tumor, and other factors. In addition, recurrence of disease is common, even among long-term survivors.
Factors that influence outcome include:
Type and grade of the tumor. Low-grade oligodendrogliomas grow more slowly and are less likely to recur. High-grade oligodendrogliomas can be harder to treat and often recur sooner.
If surgery can completely remove the tumor. One of the most important factors for prognosis is whether surgery can completely remove the tumor. Children who have a gross total resection with no visible tumor after surgery have the best chance of cure.
Whether the cancer has spread. Cancer that has metastasized or spread to other parts of the brain is harder to treat.
Location of the tumor. Tumors located in the cerebrum or cerebellum have a greater chance of cure compared to tumors in the middle of the brain or brainstem. This is largely due to how hard it is to remove the tumor with surgery.
If the cancer is new or if it has come back. Recurrent disease is harder to treat.
Molecular or genetic features of the tumor. Scientists are studying whether certain changes in genes and cell features of the tumor can make the disease easier to treat or allow for specific new emerging treatments (called targeted therapy).
Treatment of oligodendroglioma
Treatment of oligodendroglioma depends on the type of tumor, its location, and whether it has spread or come back. Aggressive tumors need more intensive treatment. Doctors also consider the age of the patient. Radiation therapy is not used in very young children because of the potential side effects.
Surgery to remove as much of the tumor as possible is the main treatment for oligodendroglioma. The goal is gross total resection, or complete removal of the tumor. However, it may not always be possible to remove the entire tumor due to risk of damage to nearby brain structures and the diffuse nature of oligodendroglioma. In some cases, surgery may not be possible due to the location of the tumor. Some patients with low-grade tumors may have surgery alone followed by observation. Other patients may have surgery and then receive radiation and/or chemotherapy.
Radiation therapy may be used after surgery to kill cancer cells left behind. Radiation therapy depends on the type and location of the tumor and the age of the child.
Chemotherapy is sometimes used in addition to surgery and radiation therapy, especially for high grade tumors. Chemotherapy may be used in infants and young children to delay the use of radiation therapy. Chemotherapy used for oligodendroglioma includes procarbazine, lomustine (CCNU), and vincristine (PCV regimen) and temozolomide. Other types of chemotherapy may also be used, especially within a clinical trial. Some chemotherapy medicines used to treat oligodendroglioma may cause fertility problems in the future. Depending on the type of chemotherapy planned, families may want to talk with their care team about options to help protect fertility.
Targeted therapies work by acting on or targeting specific features of the tumor such as genes and proteins.
Care for patients with oligodendroglioma should include appropriate referrals to support services such as neurology, rehabilitation therapy, school services, and psychology. After treatment for oligodendroglioma, patients will have regular MRI scans to monitor for recurrence. Steroid and anti-seizure medications may be needed for a period of time.
Life after pediatric oligodendroglioma
Recovery and long-term effects of oligodendroglioma in children and teens depend on features of the tumor and treatments received. Ongoing follow-up care, laboratory tests, and routine MRI scans are needed to monitor patients for recurrence or progression of disease. The care team will set a schedule based on individual patient needs.
Pediatric low-grade glioma as a long-term disease
Low-grade gliomas, including some oligodendrogliomas, are often a chronic or long-term disease. Although long-term survival from low-grade glioma is high, the tumor often comes back or progresses over time. A patient may need additional treatments over many years of follow-up. This means the patient is at risk for more treatment- or tumor- related complications. There may also be times when the tumor shows growth on a scan, but the care team recommends observation (watchful waiting) instead of treatment. Good communication and trust among patient, family, and care team are critical to aid in decision making and disease management.
An interdisciplinary care team can provide a personalized care plan to promote long-term health and quality of life. Regular checkups and health care throughout survivorship are important to watch for late effects of treatment, health problems that can develop years after therapy.