Glioblastoma

January 12, 2026

This page was reviewed under our medical and editorial policy by Rosalind Munoz, P.A., Department of Medical Oncology & Therapeutics Research, City of Hope^® Cancer Center Duarte.

Glioblastoma is the most common type of cancerous brain tumor in adults. In the United States, more than 12,000 people are diagnosed with glioblastoma each year.

What Is Glioblastoma?

Glioblastoma is a rare, aggressive brain tumor, also known as grade 4 astrocytoma, glioblastoma multiforme, GBM and GBM cancer.

Glioblastoma is a type of brain tumor that belongs to a group called astrocytomas. These tumors start in astrocytes — star-shaped cells that help feed and support the brain’s nerve cells (neurons). A glioblastoma can also contain a mix of different brain cells, including some that are no longer alive.

Glioma vs. Glioblastoma

Glioma is a broad term for tumors that start in the brain’s glial cells — the cells that support and protect nerve cells. There are several types of gliomas, and they can be low-grade (slower growing) or high-grade (faster growing). Glioblastoma is the most aggressive type of glioma, meaning it grows quickly, spreads into nearby brain tissue and is especially challenging to treat. These tumors often return after treatment.

Glioblastoma Symptoms

Glioblastoma symptoms usually happen when the tumor presses on or damages certain parts of the brain. A smaller tumor might not cause noticeable problems at first, but as the tumor grows, symptoms can develop depending on its location.

Possible symptoms include:

• Headaches
• Nausea or vomiting
• Feeling very tired or sleepy
• Weakness or numbness on one side of the body
• Trouble with memory, speech or understanding language
• Mood or personality changes
• Muscle weakness
• Blurred or double vision
• Loss of appetite
• Seizures

Glioblastoma Causes

Doctors don’t know what causes glioblastoma. Like other cancers, it starts when cells begin to grow uncontrollably and form tumors. This cell growth may have something to do with gene changes.

Risk Factors

Researchers don’t know the exact cause of glioblastoma, but certain factors can increase the chances of developing it:

• Age: Glioblastoma is most often diagnosed in older adults, especially those over 45. The average age at diagnosis is around 64.
• Gender: Men are slightly more likely than women to develop it.
• Family history: Having close relatives with gliomas or certain rare genetic conditions like neurofibromatosis type 1, Li-Fraumeni syndrome or Turcot syndrome can elevate risk.
• Previous radiation exposure: Radiation to the head and neck can increase risk years later.
• Weakened immune system: People with certain immune disorders or on long-term immune-suppressing medications may be at higher risk.

Diagnosis and Testing

To diagnose glioblastoma, doctors use various tools:

Neurological exam: Checks for problems with balance, strength, coordination, vision, hearing and other senses.

Imaging tests (like MRI scans): Determines the tumor’s size and location.

Biopsy: Involves removing a small tumor sample to see how aggressive it is and what types of cells are involved.

Molecular testing: Looks for specific genetic changes (mutations) in the tumor that can help guide personalized treatment

Grades

All glioblastomas are classified as grade 4 brain tumors — the most aggressive type — according to the World Health Organization (WHO) grading system. This means they grow and spread quickly, often forming their own blood vessels to feed the tumor. They can also invade nearby brain tissue, making them hard to fully remove.

Glioblastoma Treatment

Glioblastoma can be challenging to treat because it contains many types of cells, and treatments may affect some cells more than others.

Surgery: The first step is usually surgery to remove as much of the tumor as safely possible. Tumors in sensitive areas may not be fully removable.

Radiation therapy: After surgery, radiation therapy helps destroy remaining tumor cells and slow any that couldn’t be removed.

Chemotherapy: Drugs like temozolomide or carmustine may be used to support treatment and make radiation more effective.

Tumor Treating Fields: Also known as electric field therapy, this treatment uses electrodes on the scalp to send electrical impulses that target tumor cells without harming healthy brain cells.

Laser Interstitial Thermal Therapy (LITT): Used for recurring tumors that are hard to reach, this newer procedure uses a small laser catheter to heat and destroy cancer cells.

Who Treats Glioblastoma

When it comes to treating a rare disease like glioblastoma, it’s important to seek specialized care. The patient’s care team may consist of multidisciplinary experts, including:

• Neurologist, a doctor who specializes in diagnosing and treating brain and nervous system conditions.
• Neurosurgeon, a surgeon trained to operate on the brain and spinal cord if surgery is needed to remove the tumor.
• Radiation oncologist, who uses high-energy beams of radiation to destroy cancerous tissue.
• Neuro-oncologist, who treats cancer with drugs such as chemotherapy, immunotherapy or targeted therapy.
• Neuroradiologist, a specialist who interprets brain and spine imaging, such as MRIs or CT scans.
• Pathologist, who examines tissue samples for diagnostic purposes to help determine a treatment plan.
• Nurse navigator or oncology nurse, who helps guide patients through their care, answers questions and coordinates appointments.
• Supportive care providers, who focus on cancer- and treatment-related side effects and symptom management.

Glioblastoma Survival Rate

Glioblastoma is a challenging disease to treat, and the average survival is about 15 months.

One way researchers gauge prognosis is by looking at the five-year relative survival rate. This compares the five-year survival rates of people with a certain cancer type to those without it.

The five-year relative survival rate for glioblastoma in adults over 40 is 5.6%. This means, on average, 5 out of 100 adult patients are alive five years after diagnosis, compared to people without glioblastoma.

The five-year relative survival rate among children under the age of 14 with glioblastoma is 19.5%, and for young adults with glioblastoma between the ages of 15 and 39, it’s 27.3%.

It’s important to understand that survival statistics aren’t personalized — many factors can affect an individual’s outlook, including how much of the tumor can be removed, how it responds to treatment and what treatments are used. Speak with the neurology care team for specifics about each patient’s prognosis.