Oligodendroglioma

What an oligodendroglioma is

Glial cells support and insulate nerve cells. Oligodendrogliomas take their name from oligodendrocytes, the cells that make the fatty insulation (myelin) around nerves, because the tumor cells look similar under the microscope. They are "diffuse" tumors: they spread into surrounding brain tissue rather than forming a neat ball, so they cannot be completely removed.

Since 2016, and more firmly in the 2021 WHO classification, the diagnosis requires two molecular markers:

• IDH1 or IDH2 mutation: a change in a metabolic enzyme found in lower-grade gliomas.
• 1p/19q codeletion: loss of the short arm of chromosome 1 and the long arm of chromosome 19.

A tumor with an IDH mutation but no codeletion is classed as an astrocytoma instead. This distinction matters because codeleted tumors respond better to chemotherapy and have a better outlook.

Grades

Grade 2 tumors can progress to grade 3 over time. Oligodendrogliomas are not graded 4; the most aggressive glioma, glioblastoma, is a different tumor type.

Symptoms

Symptoms depend on where the tumor is and how fast it grows:

• Seizures: the first symptom in about two-thirds of people. They may be focal (twitching of one side, odd sensations, brief altered awareness) or generalized convulsions.
• Headaches, often with nausea, from raised pressure.
• Personality or behavior changes, reduced motivation or poor judgment, especially with frontal lobe tumors.
• Memory and concentration problems.
• Weakness or numbness on one side.
• Speech or language difficulties.
• Vision changes.

Because growth is slow, symptoms may develop gradually and be put down to stress or aging.

Causes and risk factors

The cause is unknown in most people. Known risk factors for gliomas generally are previous radiation to the head and some rare inherited syndromes. Mobile phones, diet and head injury have not been shown to cause gliomas.

Diagnosis

1. Neurological examination.
2. MRI with contrast: the main imaging test. Oligodendrogliomas usually appear in the cortex of the frontal lobe and may show little contrast enhancement in grade 2.
3. CT scan: often shows calcium deposits within the tumor, a characteristic feature.
4. Biopsy or surgery: tissue is required for diagnosis. The lab tests for IDH mutation and 1p/19q codeletion, along with other markers such as CDKN2A and TERT.
5. EEG if seizures are frequent or unclear.

Oligodendroglioma treatment

Treatment is planned by a multidisciplinary neuro-oncology team. It aims to control the tumor while protecting thinking, memory and quality of life.

Surgery

The first step is usually removing as much tumor as is safely possible. Surgeons may operate with the patient awake and use brain mapping to protect speech and movement areas. More complete removal is linked to longer survival and better seizure control.

After surgery

• Watchful waiting: for some younger people with grade 2 tumors that were largely removed and with few symptoms, regular MRI scans every 3 to 6 months may be chosen at first.
• IDH inhibitor: vorasidenib, a daily tablet approved in 2024, is used for grade 2 IDH-mutant gliomas after surgery when immediate radiotherapy and chemotherapy are not needed. It delays tumor growth and postpones the need for radiotherapy.
• Radiotherapy plus chemotherapy: for grade 3 tumors and for higher-risk grade 2 tumors (older age, residual tumor, symptoms). Chemotherapy is either PCV (procarbazine, CCNU/lomustine and vincristine) or temozolomide. Large trials showed adding PCV to radiotherapy roughly doubled survival in codeleted tumors.

Seizure control and supportive care

• Anti-seizure medicines, often long-term.
• Steroids for brain swelling around the tumor.
• Rehabilitation, including physical, occupational and speech therapy.
• Support for fatigue, mood changes and cognitive effects.

Prognosis and life expectancy

Oligodendrogliomas have the best outlook of the adult diffuse gliomas. With modern treatment, median survival for grade 2 is commonly reported at more than 15 years, and for grade 3 at more than 10 years, with many people living longer. Younger age, good functional status, more complete removal and grade 2 are linked to better outcomes. The tumor usually recurs eventually, so follow-up scans continue lifelong. Late effects of radiotherapy on memory and thinking are a consideration in planning treatment.

Many people continue working, driving (once seizure-free for the legally required time) and living active lives for years.

Frequently asked questions

What is the life expectancy with oligodendroglioma?

It is generally long compared with other brain tumors. Median survival is often reported at more than 15 years for grade 2 and more than 10 years for grade 3 with current treatment. Individual outlook depends on age, symptoms, how much tumor was removed and response to therapy.

Is oligodendroglioma cancer?

Yes. It is a primary malignant brain tumor, because it infiltrates surrounding brain tissue and cannot usually be cured by surgery alone. It rarely spreads outside the brain. Grade 2 tumors grow slowly, sometimes for many years before needing treatment beyond surgery.

What are the first symptoms of oligodendroglioma?

The most common first symptom is a seizure, which happens in about two-thirds of people. Others notice headaches, personality or behavior changes, memory problems, or weakness or numbness on one side. Symptoms often develop slowly over months or years.

What does 1p/19q codeletion mean?

It means the tumor cells have lost the short arm of chromosome 1 and the long arm of chromosome 19. Together with an IDH mutation, it defines oligodendroglioma. Codeleted tumors respond particularly well to chemotherapy and radiotherapy and have a better prognosis.

Can oligodendroglioma be cured?

It is rarely cured, because tumor cells spread into nearby brain tissue. However, treatment can control it for many years, and some people live for decades. Ongoing research into IDH inhibitors and other targeted treatments continues to improve outcomes.