Oligodendroglioma, IDH-mutant, and 1p/19q-codeleted

What is an oligodendroglioma?

An oligodendroglioma is a rare type of glioma brain tumour that forms when certain support cells in the brain – called oligodendrocytes – start to grow out of control. These cells normally help protect and insulate nerves to speed up nerve signals. Depending on their behaviour and how fast they grow, oligodendrogliomas are groups into two grades:

Grade 2
These tumours grow slowly and may not cause symptoms for a long time. They are usually monitored closely and treated if they start to grow or cause problems.

Grade 3 (also called anaplastic oligodendroglioma)
These grow more quickly and may need more intensive treatment, such as surgery, radiotherapy, and chemotherapy.

Doctors use specific genetic markers (changes to the DNA) to diagnose this tumour and guide treatment decisions. Two important features are:

A mutation in a gene called Isocitrate dehydrogenase IDH – this can be either IDH1 or IDH2

A combined loss of parts of chromosomes 1 and 19 (called 1p/19q codeletion)

Acknowledging the changes above, the World Health Organization 2021 classification of central nervous system tumours refer to oligodendrogliomas as “Oligodendroglioma, IDH-mutant, and 1p/19q-codeleted”.

What are the symptoms of an oligodendroglioma?

Symptoms of an oligodendroglioma, can vary depending on the tumour’s location in the brain, but common signs include:

  • Persistent headaches, often worse in the morning

  • Seizures, which can vary in type and severity

  • Nausea and vomiting, especially in the morning

  • Vision problems, such as blurred or double vision (diplopia)

  • Cognitive or personality changes, including memory issues and confusion

  • Weakness or numbness on one side of the body

  • Speech difficulties

How is an oligodendroglioma diagnosed?

  • Initial brain imaging

    The first step is usually a magnetic resonance imaging (MRI) scan. This provides detailed images of the brain and helps doctors identify any abnormal areas. Special types of MRI may be used to assess how the tumour is behaving and whether it looks slow-growing (grade 2) or more aggressive (grade 3).

  • Referral to a specialist team

    If a tumour is suspected, the patient is referred to a multidisciplinary team (MDT) of specialists. This team may include neurologists, neurosurgeons, oncologists, radiologists, and specialist nurses who work together to plan the next steps.

  • Tissue sampling (biopsy)

    To confirm the diagnosis, a small sample of the tumour is taken – usually through a surgical procedure (can be combined with surgical tumour removal). This sample is examined under a microscope to determine the exact type of tumour.

  • Molecular and genetic testing

    The tumour sample is tested for specific genetic changes. For oligodendroglioma, doctors look for a mutation in the IDH gene and a combined loss of parts of chromosomes 1 and 19 (called 1p/19q codeletion). Both features must be present to confirm the diagnosis.

  • Further testing (if needed)

    Sometimes, more scans or tests are done to get extra information about the tumour or to help plan surgery or other treatments. This might include functional MRI, CT scans, or spinal fluid tests.

What are the treatments for oligodendroglioma?

The medical team aims to remove as much of the tumour as safely possible. This helps reduce pressure in the brain and provides tissue needed to confirm the diagnosis. If the tumour is in a sensitive area of the brain, complete removal may not be possible.

  • Surgery

    The medical team aims to remove as much of the tumour as safely possible. This helps reduce pressure in the brain and provides tissue needed to confirm the diagnosis. If the tumour is in a sensitive area of the brain, complete removal may not be possible.

  • Active monitoring

    If the tumour is slow-growing (grade 2) and not causing symptoms, the care team may recommend regular monitoring. This involves routine MRI scans and check-ups to watch for any changes before starting, or following, treatment.

  • Radiation therapy

    Radiotherapy uses high-energy rays to kill cancer cells. It’s often used after surgery to lower the chance of the tumour coming back. It can also be used if surgery isn’t possible or to help with symptoms.

  • Chemotherapy

    Chemotherapy uses drugs to kill or stop the growth of cancer cells. It is often used alongside radiotherapy or as a follow-up (adjuvant) treatment.

    For oligodendroglioma, the standard treatment is a combination called PCV (procarbazine, lomustine [CCNU], and vincristine). In some cases, temozolomide may be considered.

  • Clinical trials

    Patients may be offered the chance to take part in clinical trials. These trials test new treatments and may provide access to promising therapies while helping improve care for future patients.

  • Supportive care

    Supportive care helps manage symptoms such as swelling, seizures, tiredness, or mobility issues. This may include steroids, anti-seizure medication, physiotherapy, occupational therapy and emotional support.

  • Follow-up care

    After treatment, patients are followed up with regular MRI scans and appointments to check for any signs of the tumour returning or growing. The care plan is adjusted as needed.

  • Recurrent oligodendroglioma

    If the tumour comes back, treatment options may include more surgery, additional chemotherapy (such as PCV or lomustine [CCNU]) or radiotherapy. The care team will tailor the approach based on the patient’s previous treatments and current condition.

What are they looking for with molecular and genetic testing?

Doctors carry out genetic testing on oligodendroglioma tumours to help confirm the diagnosis, understand how the tumour is likely to behave, and decide on the best treatment. These tests are done on a sample of the tumour, usually taken during surgery or a biopsy.

  • IDH mutation

    The tumour is tested for mutations in the IDH1 or IDH2 genes. If one of these mutations is found, the tumour is classified as “IDH-mutant”, which is a key feature of oligodendroglioma.

  • 1p/19q codeletion

    The tumour is also tested for a combined loss of parts of chromosomes 1 and 19, known as 1p/19q codeletion. This genetic signature must be present, along with the IDH mutation, to confirm the diagnosis of oligodendroglioma.

  • MGMT promoter methylation

    Sometimes, a tumour has a change called MGMT promoter methylation. This means a gene that normally helps repair damaged DNA is turned off. When this happens, chemotherapy – especially drugs such as temozolomide and PCV – can work better because the tumour cells can’t fix the damage the treatment causes. People with this gene change often respond more positively to treatment and may have a better outcome.

What is the prognosis for an oligodendroglioma?

The prognosis for oligodendroglioma is generally positive. People with grade 2 tumours often live for many years with regular monitoring or treatment, while those with grade 3 tumours may also have a good outlook, especially when the tumour responds well to surgery, radiotherapy, or chemotherapy. The presence of certain genetic features is linked to longer survival and better treatment response.

What causes an oligodendroglioma brain tumour?

The exact cause is unknown. Most cases occur sporadically without a clear genetic or environmental trigger. Research is ongoing to better understand the underlying mechanisms and risk factors.

Learn more about brain tumour causes

Doctors use a system to group (classify) brain tumours into different groups and types. The World Health Organisation (WHO) regularly update this system. The information in this page is based on the latest WHO classification of 2021.