Glioblastoma

What is it?

Glioblastoma is a brain cancer that starts in astrocytes, star-shaped cells that help keep nerve cells healthy. Doctors call it a grade 4 tumour: it grows and spreads very quickly, and its cells look very different from normal cells.

It is the most common brain cancer in adults, making up about 35 to 40 in every 100 cancers that start in the brain, and it is more common in men. The cause is not known, and few risk factors are known; radiation to the head in the past raises the risk. Some genetic conditions that run in families, such as neurofibromatosis and Li-Fraumeni syndrome, may raise the risk of brain tumours.

The first signs

The signs depend on where the tumour is and how big it is.

• new or worsening headaches, often in the morning;
• feeling or being sick;
• seizures (fits);
• problems with vision, hearing or speech;
• changes in mood, personality or concentration;
• weakness, balance problems or trouble walking.

How doctors find out

A doctor checks how your brain, nerves, muscles and senses are working, and you may have brain scans, such as MRI or CT, to look for a tumour. Usually a small sample of the tumour (a biopsy) is taken, with a needle or during an operation, and a specialist looks at the cells to find out the type and grade. Tests on the tumour's genes help to plan treatment. A team of specialists guides you through the tests and treatment, and a specialist nurse is your main contact.

Current treatment

For adults under 70 in good general health: surgery to remove as much of the tumour as is safe, then radiotherapy with temozolomide chemotherapy, followed by six cycles of temozolomide.

Will it get worse?

Glioblastoma grows fast and usually cannot be removed completely by surgery. How it goes depends on the type and grade of the tumour, where it is, whether surgery can remove it, whether cancer cells are left after surgery, changes in its chromosomes, whether it is new or has come back, and your general health. NCI experts wrote in 2017 that about 15 in every 100 people were alive 5 years after diagnosis, up from almost none in the mid-1990s.

Medicines: what helps, and what to watch for

After surgery, most people have radiotherapy together with temozolomide, a chemotherapy medicine taken every day, and then temozolomide on its own. Chemotherapy can also be placed into the brain during the operation. If the cancer comes back, a targeted medicine called bevacizumab may be used. Other medicines control seizures, reduce swelling in the brain and ease pain.

Good to know:

• your care team will explain the side effects of your own treatment plan;
• You will have regular check-ups during and after treatment, and you may also have tests and scans.

Surgery and radiotherapy

For most people, surgery comes first: the surgeon removes as much of the tumour as possible. The operation can also take a sample for testing, or drain fluid that has built up. Radiotherapy uses high-energy rays aimed carefully at the tumour; you may have it after surgery to help stop the cancer coming back. A typical course is 30 treatments over 6 weeks.

Is there a cure?

No cure has been found yet. A grade 4 tumour usually cannot be removed completely. If a cure is not possible, treatment aims to limit the cancer and its symptoms and help you live longer. Researchers are testing new treatments in people, such as immunotherapy (medicines that use the immune system to fight cancer) and targeted drugs for brain tumours with certain gene changes. You can join a clinical trial before, during or after your first treatment.

See the 461 trials you can join

Median survival

About 15 to 18 months

Sources

Written in plain words by Frontlight from these pages:

1. NCI: Glioblastoma – Unraveling the Threads to Make Progress (Cancer Currents, 3 Aug 2017)
2. NCI: Advances in Brain and Spinal Cord Tumor Research
3. NCI PDQ: Adult Central Nervous System Tumors Treatment (PDQ) – Patient Version (updated 14 Oct 2026)
4. EANO: EANO guidelines on the diagnosis and treatment of diffuse gliomas of adulthood (Weller et al., Nat Rev Clin Oncol 18:170-186), 2021
5. NHS: Malignant brain tumour – Symptoms
6. MedlinePlus: Brain Tumors
7. NHS: Malignant brain tumour – Tests and next steps
8. NHS: Malignant brain tumour – Treatment