Malignant Oligodendroglioma

Malignant oligodendroglioma is a fast-growing brain tumor that requires prompt treatment, but advances in understanding its genetic characteristics have improved outcomes for many patients.

Table of contents

• What is Malignant Oligodendroglioma?
• Where the Tumor Forms
• Signs and Symptoms
• What Causes This Tumor
• Who Gets Oligodendroglioma
• How Doctors Diagnose It
• Treatment Approaches
• What to Expect

What is Malignant Oligodendroglioma?

Malignant oligodendroglioma, also known as grade 3 oligodendroglioma or anaplastic oligodendroglioma, is a type of brain tumor that grows in the brain or, very rarely, in the spinal cord^[1]. These tumors develop from cells called oligodendrocytes, which are support cells in the nervous system that help protect nerve fibers^[1].

Grade 3 oligodendrogliomas are considered malignant because they are fast-growing tumors that spread to nearby brain tissue^[6]. This makes them more aggressive than grade 2 (low-grade) oligodendrogliomas, which grow slowly^[1]. Sometimes a low-grade tumor can progress over time and become a grade 3 tumor, or the tumor may appear as grade 3 from the start^[5].

Oligodendrogliomas belong to a larger group of tumors called gliomas, which come from glial cells—the support cells of the nervous system^[1]. These tumors account for between 5% and 15% of all gliomas and about 3% to 4% of all brain tumors^[1]. An estimated 14,950 Americans are living with this tumor^[2].

• Brain (cerebral cortex)
• Frontal lobe
• Temporal lobe
• Spinal cord (rare)

Where the Tumor Forms

Oligodendrogliomas are commonly found in the white matter and the outer layer of the brain called the cerebral cortex^[6]. The cortex is the wrinkly outer surface of your brain that controls many abilities you use every day, such as vision, language, and muscle control^[1].

Most often, these tumors develop in the brain’s frontal or temporal lobes^[5]. The frontal lobe, located behind the forehead, coordinates tasks like voluntary movement, speech, and reasoning. The temporal lobe is located at the sides of the brain, above the ears, and is responsible for hearing and memory^[5]. However, oligodendrogliomas can form anywhere in the central nervous system^[6].

These tumors rarely spread outside the brain and spinal cord to other organs^[6]. However, they can spread to other areas of the central nervous system through cerebrospinal fluid (the liquid that surrounds the brain and spinal cord), though this is uncommon^[6].

Signs and Symptoms

Because oligodendrogliomas grow slowly at first, symptoms may not appear for many years^[3]. However, malignant grade 3 tumors grow more quickly and are more likely to cause noticeable symptoms^[8].

The most common symptom is a seizure, which happens in up to 80% of people with oligodendroglioma^[1]. Around 60% of people have a seizure before being diagnosed^[6]. This happens because these tumors often affect the cerebral cortex, which controls many body functions^[1].

Other common symptoms include^[6]:

• Headaches
• Problems with thinking and memory
• Weakness in parts of the body
• Numbness or tingling
• Problems with balance and movement

Oligodendrogliomas may also cause focal symptoms—problems focused in a specific area of the brain. These symptoms depend on where the tumor is located and usually affect a body part or an ability^[1]. Examples include:

• Muscle weakness or paralysis, especially on one side of the body or face
• Hearing loss
• Trouble speaking or understanding others who are talking (called aphasia)
• Vision loss, double vision, or blurred vision
• Changes in personality or behavior

What Causes This Tumor

All oligodendrogliomas happen because of two specific DNA changes in the tumor cells. By definition, a tumor must have these genetic alterations to be diagnosed as an oligodendroglioma^[6]:

First, there is a change called 1p/19q co-deletion. This means that parts of two chromosomes (chromosome 1 and chromosome 19) are missing in the tumor cells^[1]. Chromosomes are the structures in cells that carry genetic information.

Second, there is a mutation in the IDH gene (isocitrate dehydrogenase). This is an enzyme found in cells^[8]. These genetic changes help doctors confirm the diagnosis and choose the best treatment^[8].

The cause of most oligodendrogliomas is not known^[6]. However, exposure to radiation and certain gene changes that can be passed down through families have been linked to a higher chance of developing oligodendrogliomas^[6].

Who Gets Oligodendroglioma

Oligodendrogliomas occur in people of any age but are most common in those between the ages of 35 and 44^[6]. Most people who have it are between the ages of 40 and 50^[1]. These tumors are most common in adults but can happen at any age^[3]. They are rare in children^[6].

Oligodendrogliomas occur more often in males than in females^[6]. They are most common in non-Hispanic white people^[6]. Worldwide, healthcare providers diagnose just under 24,000 people with oligodendroglioma each year^[1].

How Doctors Diagnose It

Diagnosing oligodendroglioma involves several steps. Your doctor will start with a physical examination and neurological examination^[10]. During this exam, the doctor asks about your symptoms and checks your vision, hearing, balance, coordination, strength, and reflexes. Problems in one or more of these areas can give clues about which part of the brain might be affected^[10].

Your doctor will order imaging tests such as an MRI (magnetic resonance imaging)^[10]. MRI uses a magnetic field and radio waves to create detailed images of the brain. These images help determine where the tumor is located and its size^[10]. Oligodendrogliomas usually appear as a single tumor with well-defined borders, and they tend to have some swelling around them^[6].

To confirm the diagnosis, doctors need to examine tumor tissue under a microscope. This tissue is usually obtained during surgery to remove the tumor^[6]. If surgery isn’t possible because the tumor is in a hard-to-reach location, a biopsy (taking a small sample of tissue with a needle) may be performed instead^[10].

A specialist called a neuropathologist examines the tumor tissue^[6]. The tissue undergoes biomarker testing to check for the specific genetic changes—the IDH mutation and the 1p/19q co-deletion—that confirm an oligodendroglioma diagnosis^[8]. These tests also help doctors predict how the tumor will respond to treatment^[8].

Treatment Approaches

Treatment for malignant oligodendroglioma usually involves a combination of approaches. Surgery is often the first step when the tumor is in a location that can be safely reached^[5]. The goals of surgery are to remove as much of the tumor as possible and to gather tissue for diagnosis^[8].

Because grade 3 oligodendrogliomas are malignant and fast-growing, additional treatment is usually needed after surgery^[1]. Radiation therapy is often recommended, especially if some tumor remains after surgery or if the tumor’s characteristics suggest it may come back^[8]. Radiation therapy generally takes place over six weeks and may be given along with chemotherapy^[8].

Chemotherapy uses drugs to kill cancer cells. Common chemotherapy drugs for oligodendroglioma include temozolomide, or a combination called PCV (procarbazine, lomustine, and vincristine)^[4]. These may be given as pills or through a vein. The good news is that oligodendrogliomas with the 1p/19q co-deletion tend to respond well to chemotherapy^[4].

In cases where the tumor is in a location that makes surgery difficult or impossible, treatment may involve careful monitoring, radiation therapy, and chemotherapy without surgery^[5]. Your healthcare team will likely monitor the tumor closely even after treatment^[3].

What to Expect

Experts consider oligodendroglioma a very treatable tumor, even when it is malignant^[1]. Oligodendrogliomas generally respond favorably to treatment that includes surgery, radiation, and chemotherapy, leading to better outcomes than other types of gliomas^[4].

The tumor’s genetic characteristics play an important role in determining outcomes. Tumors with the 1p/19q co-deletion are more susceptible to treatment^[8]. This genetic feature is considered a positive sign and often means a better response to therapy.

Regular follow-up care is essential after treatment. Your healthcare team will schedule ongoing imaging scans to monitor for any signs that the tumor has returned^[3]. Many patients live for years after treatment, and some experience long periods without the tumor returning.