Astrocytoma, IDH-mutant

What is an astrocytoma, IDH-mutant?

Astrocytoma, IDH-mutant, is a type of glioma – a brain tumour that arises from astrocytes, which are supportive glial cells in the brain. It is most commonly diagnosed in young to middle-aged adults and is a diffuse tumour, which means it has no clear edge and infiltrates surrounding brain areas.

Astrocytoma IDH-mutant tumours are grouped into grades 2, 3, or 4, which reflect how the tumour behaves:

Grade 2 (low-grade): initially a slow-growing tumour

Grade 3 (high-grade): faster-growing, more likely to spread

Grade 4 (high-grade): the most aggressive, often showing signs like dead tissue (necrosis)

According to the World Health Organization’s 2021 classification of brain tumours, astrocytoma, IDH-mutant is a type of tumour defined by a specific change – called a mutation – in one of two genes known as IDH1 or IDH2.

All diffuse astrocytomas are now grouped under the classification astrocytoma, IDH-mutant. However, there are other types of tumours that also develop from astrocytes but have different characteristics. These include glioblastoma, pilocytic astrocytoma, pleomorphic xanthoastrocytoma (PXA) and subependymal giant cell astrocytoma (SEGA).

What are the symptoms of an astrocytoma?

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

Common symptoms include:

  • Persistent headaches, often worse in the morning

  • Weakness or numbness on one side of the body

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

  • Cognitive or personality changes

  • Seizures

  • Nausea and vomiting

  • Speech difficulties
More information on brain tumour symptoms

How is an astrocytoma 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 shows signs of being aggressive.

  • 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.

    One key test looks for changes in the DNA of the IDH1 and IDH2 genes. If the tumour sample has these changes, then they are astrocytoma, IDH-mutant. This information helps doctors understand how the tumour is likely to behave, and which treatments may be most effective.

  • Further testing (if needed)

    In some cases, additional imaging or tests may be used to gather more information about the tumour or to help plan surgery or other treatments.

What are the treatments for astrocytoma?

The main treatments for astrocytoma are surgery, radiotherapy and chemotherapy, but treatment depends heavily on the grade of the tumour, mutations in certain genes and its location.

Here is an overview of the primary treatment options:

  • Surgery

    The aim is to remove as much of the tumour as possible while preserving critical brain functions. Surgery also provides tissue for histological and molecular analysis, which is essential for confirming the diagnosis and guiding further treatment. However, complete removal may not be possible if the tumour is in an area of the brain that are too risky to operate on.

  • Active monitoring

    For lower grade tumours, patients may be recommended active monitoring. They will undergo regular scans to assess how the tumour is growing.

  • Radiation therapy

    Radiotherapy is typically offered after surgery to destroy any remaining cancer cells and reduce the risk of recurrence. It may also be used as the main treatment when surgery is not possible or as a palliative option to relieve 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. In astrocytoma, the commonly considered chemotherapy drugs are:

    Temozolomide – an oral chemotherapy agent that is typically given to higher grade astrocytoma patients

    PCV – a combination of chemotherapy drugs, including procarbazine, lomustine (CCNU) and vincristine, typically gives to lower grade astrocytoma patients

  • Clinical trials

    Clinical trials are essential for developing new treatments and improving outcomes. Patients may benefit from access to innovative therapies and enhanced monitoring. Participation also contributes to research that may help future patients.

  • Supportive care

    Supportive care is vital throughout treatment to manage symptoms such as pain, seizures, fatigue, and neurological issues. This may include:

    Steroids to reduce swelling

    Anti-seizure medications

    Physiotherapy and occupational therapy to support mobility and daily functioning

  • Follow-up care

    After initial treatment, patients undergo regular follow-up, including MRI scans, to monitor for tumour recurrence or progression. Ongoing consultations help adjust treatment plans.

  • Recurrent astrocytoma

    For astrocytoma’s that recur after first-line treatment, patients may be offered a range of options tailored to their individual circumstances. Common approaches include additional cycles of chemotherapy—typically with temozolomide, PCV or single-agent lomustine (CCNU). Depending on the case, the clinical team may also consider further surgery or radiotherapy.
Read more about emerging therapies

What are they looking for with molecular and genetic testing?

Doctors carry out genetic testing on astrocytoma 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. These mutations are what define the tumour as an “IDH-mutant” astrocytoma. If there is no mutation, then the tumour may be a glioblastoma.

  • 1p/19q codeletion

    The tumour is also tested for the genetic signature, 1p/19p codeletion which is found in a different type of brain tumour called oligodendroglioma. If this codeletion is present, the tumour is not an astrocytoma but an oligodendroglioma instead. So, confirming that it’s not  there helps confirm the diagnosis.

  • ATRX mutation

    A mutation in the ATRX gene is common is astrocytomas and supports the diagnosis. It also helps differentiate astrocytomas from other gliomas.

  • CDKN2A/B homozygous deletion

    For higher-grade astrocytomas, the tumour is tested for a deletion in a gene called CDKN2A/B. If both copies of this gene are missing (called a homozygous deletion), it indicates that the tumour is behaving more aggressively and should be considered grade 4, even if it doesn’t look that way under the microscope. This helps doctors decide whether more intensive treatment is needed.

  • 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 a drug called temozolomide—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 astrocytoma tumour?

Prognosis varies by tumour grade and molecular features. IDH-mutant astrocytomas generally have a better prognosis than IDH-wildtype gliomas (glioblastoma). The presence of CDKN2A/B deletion in grade 4 astrocytomas is associated with a poorer outcome.

Long-term survival is possible, especially in lower-grade tumours with favourable molecular profiles.

What causes an astrocytoma 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.

References

Overview | Brain tumours (primary) and brain metastases in over 16s | Guidance | NICE

NHS England » Clinical Commissioning Policy: Stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) to the surgical cavity following resection of cerebral metastases (All ages)