Astrocytoma IDH-mutant and glioblastoma IDH-wildtype are two of the most aggressive and complex types of brain tumours. But a question we are often asked is: “What is the difference, and what does it mean for researchers and patients?”
What is glioblastoma?
Glioblastoma tumours are fast-growing, aggressive grade 4 tumours that are very difficult to treat and have a poor prognosis. This is the most aggressive and most common type of primary brain tumour in adults, with around 3,200 people diagnosed each year in the UK. All glioblastomas are grade 4 tumours and have an average survival of 12-18 months.
What is astrocytoma?
Astrocytoma tumours can be grade 2, 3 or even 4, reflecting how the tumour behaves and with implications for treatment and prognosis. They can start at a lower grade and progress to higher grades over time. Although higher grades have a poor outlook, they generally have a better prognosis than glioblastoma.
Why is there confusion between the two?
Astrocytoma and glioblastoma are both forms of glioma. These are brain tumours that develop from glial cells, which normally support and protect neurons in the brain and spinal cord. Gliomas can be slow-growing (low-grade) or fast-growing (high-grade) and can affect adults and children differently.
Astrocytoma and glioblastoma both arise from astrocytes (star-shaped glial cells). Historically, glioblastoma was often used as a catch-all term for grade 4 astrocytoma, even those that started as a lower grade and progressed.
Today, thanks to advances in diagnosis, astrocytoma and glioblastoma are now defined as distinct tumour types with no overlap. This distinction reflects differences in how quickly they grow, how they respond to treatment and life expectancy.
What makes astrocytoma and glioblastoma different?
Doctors use an international system developed by the World Health Organization (WHO) to classify and diagnose brain tumours.
The latest edition, the 2021 WHO Classification of Central Nervous System Tumours, introduced a major change: moving from classification based on cell appearance (histology) to molecular classification – based on changes inside the cell.
Glioblastoma cancer cells
As a result of this update, astrocytoma and glioblastoma are separated by whether they have a mutation (change) in genes that code for the production of an enzyme known as isocitrate dehydrogenase (IDH). The genes are known as IDH1 and IDH2.
A tumour that has a mutation in the IDH1 or IDH2 gene is classified as astrocytoma, IDH-mutant.
A tumour that does not have a mutation in the IDH1 or IDH2 gene is classified as glioblastoma, IDH-wildtype.
What is IDH?
IDH is an enzyme involved in cell metabolism. Mutations in the genes that make this enzyme lead to the production of a compound called d-2-hydroxyglutarate, which disrupts normal cell development and contributes to tumour growth. If tumour cells carry these mutations, they tend to respond better to treatment and be less aggressive than IDH wildtype tumours.
Why is it important that astrocytoma and glioblastoma are separated?
In the past, many clinical trials for brain tumours have failed – not always because the treatments didn’t work, but because researchers didn’t fully understand the differences between tumours.
For years, glioblastoma and astrocytoma were often treated as if they were the same disease. However, we now know they have a different biology and behaviour. A therapy being tested may have proven effective for some patients involved in a clinical trial, but when results were averaged across the whole trial cohort, the therapy would have looked like a failure. Really, the problem was that patients with fundamentally different tumours were being treated with the same approach.
Astrocytoma cancer cells
Even today, doctors see “exceptional responders” – patients who respond far better than expected to certain treatments. These cases prove that understanding what makes one tumour different from another is critical.
By understanding these differences, we can design treatments that truly work for each patient, rather than relying on one-size-fits-all treatment strategy.
How is Brain Tumour Research helping to find a cure for astrocytoma and glioblastoma tumours?
Our investment in Centres of Excellence is driving world-class research into these complex tumours, bringing together leading researchers, cutting-edge technology and collaborative expertise to unravel the biology of these tumours, identify new treatment targets and accelerate progress towards a cure.
Our Centre of Excellence at Queen Mary University of London is developing personalised treatments for adult glioblastoma patients. The Centre, located at the Blizard Institute, London, and led by Professor Silvia Marino, has developed a state-of-the-art method to compare healthy and cancerous cells from the same patient to understand how tumour cells control gene expression (turn genes on or off). This method has allowed researchers to identify genes that are essential for tumour growth specific to each patient, which could be targeted with repurposed drugs. It has already pinpointed several key genes for tumour growth and helped researchers understand how these genes are controlled. It has also revealed new sub-groups of glioblastoma with implications for treatment.
Our Centre at the University of Plymouth is also delving into research into astrocytoma following a funding boost in October 2025. Research groups are exploring whether drugs used in combination with temozolomide can improve treatment for IDH-mutant gliomas and targeting a family of proteins called GBPs, which usually help fight infections but also seem to support tumour growth and help IDH-mutant gliomas hide from the immune system.
Our Scottish Brain Tumour Research Centre of Excellence is dedicated to advancing the development of new treatments for glioblastoma. They are using a multidisciplinary approach for drug discovery and preclinical testing to provide the data needed to attract the investment that funds clinical trials. The Centre will increase the number of trials available for glioblastoma patients in Scotland and beyond.
Your donations make this vital research possible. Please donate what you can today or set up a regular donation to help fund the fight against all types of brain tumours.
Related reading:
