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Maurie Markman, MD, President, Medicine & Science

This page was reviewed on June 8, 2022.

Glioblastoma is a form of brain cancer that grows and spreads very quickly. Treatments are designed to slow down its growth and help relieve symptoms.

This article will cover:

What is glioblastoma?

Glioblastoma, formerly called glioblastoma multiforme or GBM, starts in brain cells called glial cells. Specifically, it starts in the star-shaped glial cells known as astrocytes. Astrocytes help the nerve cells in the brain develop and function properly.

According to the National Cancer Institute, glioblastomas are the most common type of brain tumor in adults, accounting for at least 35 percent to 40 percent of all cancerous brain tumors. About 14,000 people are diagnosed with glioblastoma every year. Men get glioblastomas more often than women. Most people who are diagnosed are older, between ages 45 and 70, but people of any age can develop glioblastoma.

Glioblastoma causes and risk factors

Scientists don’t know what causes glioblastoma. Although they haven’t discovered a single risk factor, glioblastoma has been associated with:

  • Previous treatment with radiation therapy 
  • Some genetic (hereditary) conditions that cause tumors, including Lynch, Turcot and Li-Fraumeni syndromes, and neurofibromatosis type 1 (NF1). Although people with these syndromes do sometimes develop glioblastoma, it’s rare. Glioblastoma itself isn’t considered hereditary.
  • Exposure to certain toxic chemicals

Learn more about brain cancer causes and risk factors

Glioblastoma symptoms

Glioblastomas can grow anywhere in the brain. The rapid growth of the tumor can put pressure on the brain and cause the following symptoms, which are typically worse in the morning:

Where a tumor is located in the brain can determine what kind of effects it has, such as:

Other symptoms may include:

  • Seizures
  • Mood or personality changes
  • Vision problems
  • Speech problems that gradually get worse

Symptoms may come on suddenly or slowly get worse.

How glioblastomas are diagnosed

The patient's care team will use various imaging techniques, such as magnetic resonance imaging (MRI) or a computed tomography (CT) scan (also called a CAT scan), to take pictures of his or her brain and look for a tumor.


An MRI machine uses radio waves and magnets to create images of the brain. The patient may have an MRI without contrast or an MRI with contrast, which means the nurse or technician who does the MRI injects a contrast dye into the patient's arm. This helps show the location of the tumor as a bright area on the scan.

The patient's doctor may recommend other kinds of MRI tests, called functional MRI (fMRI) and MRI spectroscopy (MRS).

  • A functional MRI shows which sections of the brain are threatened by the tumor and can help in planning surgery to remove the tumor. During an fMRI, the patient will be asked to do certain tasks such as raising his or her arm or speaking, while the imaging screen shows which area of the brain is active.
  • MRI spectroscopy can help doctors find out more about a suspected tumor without doing a biopsy. MRS can show levels of different chemicals in the brain that might indicate whether a tumor is present.

CT scan

CT scans use X-rays to produce three-dimensional images that can evaluate a tumor’s size. They can also show any bleeding or enlargement of the fluid-filled ventricles in the brain. Some CT scans use a contrast medium, which may be taken by mouth or injected into a vein.

If a tumor is found, the patient may have a biopsy, which takes a small amount of tissue from the tumor so it can be analyzed to see what kinds of cells are present and how aggressive the tumor is. Glioblastoma is hard to treat, and this information may help the doctor decide which treatments may work best for that particular tumor.


Doctors use a grading system for brain tumors that indicate how fast they grow. Grade 4 is the highest grade and has the most challenging course. All glioblastomas are considered grade 4 glioblastoma, which means they grow quickly and are very aggressive.

Glioblastoma treatment

Because glioblastomas are difficult to treat, treatments are designed to help the patient live longer, have fewer symptoms and better quality of life. Treatment includes surgery, followed by radiation therapy and chemotherapy.

The goal of surgery is to remove as much of the tumor as possible without harming the rest of the brain. Because of the way glioblastomas grow, with cancer cells extending into normal brain tissue, it’s difficultif not impossibleto remove all the cancer cells. However, surgery reduces pressure inside the skull, which may help lessen symptoms. It may also remove the parts of the tumor that are more resistant to radiation therapy and chemotherapy.

After the patient has recovered from surgery, he or she may undergo radiation therapy to kill remaining cancer cells. External radiation therapy uses a machine that aims high-energy beams at the site of the tumor and the surrounding area. These treatments may be delivered once daily, five days a week, for two to six weeks. Radiation therapy does cause some damage to healthy tissue, but it may help lengthen survival. Another form of radiation therapy, called radiosurgery, may be used on glioblastoma that starts growing again. This kind of radiation focuses tightly on the tumor so it causes less damage to healthy tissue.

The patient may undergo chemotherapy along with radiation. He or she may take the drug temozolomide daily during radiation therapy, then continue taking it in 28-day cycles after radiation is finished. During each cycle, there will be certain days when the patient takes the drug and other days when his or her body rests and recovers.

A technique called tumor treating fields (TTF) uses electrical fields to slow down the growth of cancer cells. The patient wears a battery-powered device that creates the fields. TTF may be used with temozolomide after initial radiation therapy. It may cause some skin irritation.

Other forms of chemotherapy, immunotherapy and targeted therapy may be used to slow the cancer’s progression after initial treatment. The patient's doctor may also suggest participating in a clinical trial of a new drug or therapy that’s being studied. Clinical trials test and refine new treatments. They can give patients access to experimental treatments that may become standard in the future.

Glioblastoma signs of decline

Because glioblastoma is difficult to treat, the patient's symptoms will eventually get worse. He or she may be sleepy and spend more time sleeping, and the patient may have headaches and nausea. It’ll get harder to move and speak, and the patient may have problems swallowing or seeing. Some people experience mood and personality changes. Talk to the cancer team about palliative care, which helps manage symptoms and ease discomfort. Patients can receive palliative care while receiving other treatment, such as chemotherapy and radiation therapy.

Glioblastoma survival rate

While overall survival rates from glioblastoma are low, each patient is different and many factors influence how long someone survives with glioblastoma. For example, the American Cancer Society (ACS) notes that the five-year relative survival rates for glioblastoma patients can vary by age:

  • 22 percent for people aged 20 to 44
  • 9 percent for people aged 45 to 54
  • 6 percent for people aged 55 to 64

Researchers continue to study new treatments that may help patients live longer. According to the National Cancer Institute, the average time of survival after glioblastoma diagnosis was eight to 10 months in the 1990s, but it’s now almost twice as long at 15 to 18 months. Overall, 15 percent of people are still alive five years after diagnosis.

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Show references
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  • American Brain Tumor Association (2022). Glioblastoma (GBM).
  • National Center for Advancing Translational Sciences, Genetic and Rare Diseases Information Center (2015, January). Glioblastoma.
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  • American Brain Tumor Association (2022). Treatments and Side Effects.
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  • American Society of Clinical Oncology (2021, November). Brain Tumor: Types of Treatment
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