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What Is Glioblastoma?

Medically Reviewed by Melinda Ratini, DO, MS on April 20, 2022

Glioblastoma is a type of brain cancer. It’s the most common type of malignant brain tumor among adults. And it is usually very aggressive, which means it can grow fast and spread quickly.

Although there is no cure, there are treatments to help ease symptoms.

Where It Forms in the Brain

Glioblastoma is a type of astrocytoma, a cancer that forms from star-shaped cells in the brain called astrocytes. In adults, this cancer usually starts in the cerebrum, the largest part of your brain.

Glioblastoma tumors make their own blood supply, which helps them grow. It's easy for them to invade normal brain tissue.

How Common Is It?

Brain cancers aren’t common. And when they do happen, about 4 out of 5 aren’t glioblastomas. Men are more likely to get them than women. And chances go up with age. Doctors diagnose about 14,000 glioblastoma cases in the U.S. each year.

Symptoms

Because glioblastomas grow quickly, pressure on the brain usually causes the first symptoms. Depending on where the tumor is, it can cause:

Causes and Risk Factors

Experts aren’t exactly sure what causes glioblastoma. But certain things may make you more likely to have one, such as:

Prior radiation to the head. If you previously got radiation to treat brain tumors or cancers that may have spread to the area, it can increase your risk for glioblastoma.

Rare genetic conditions. If you have hereditary disorders linked to genetic mutations such as:

Exposure to chemicals and other cancer-causing agents may also increase your risk for genetic mutations.

Age and gender. It’s more common among those who are 50 or above. The average age for diagnosis is 64. Men are more likely to have it.

Race. It’s more common among white people than among Black, Asian, and Indigenous groups.

Types

There are two types:

Primary glioblastoma. It makes up around 90% of the cases. This type of tumor tends to be aggressive and grows fast. It’s more likely to affect older people. You’re also likely to have a shorter life expectancy.

Secondary glioblastoma. This type usually develops from a low-grade glioma – a type of tumor found in the brain or spinal cord. It’s more likely to affect younger people, and it’s usually in the frontal lobe of the brain. The survival rate for this type tends to be better than for primary glioblastoma.

Diagnosis

A neurologist (a doctor who specializes in diagnosing and treating brain disorders) will give you a complete exam. You may get an MRI or CT scan and other tests, depending on your symptoms.

Stages

Doctors don’t group glioblastoma by stages. Instead, they give all brain cancers a “grade.” It ranges from 1 to 4. The grade is based on how the cancer cells look under a microscope and how likely they are to reproduce. Glioblastomas are always recognized as grade 4 brain cancer. That’s because this type is very aggressive and the cancer cells multiply quickly.

Treatment

The goal of glioblastoma treatment is to slow and control tumor growth and help you live as comfortably and as well as possible. There are four treatments, and many people get more than one type:

Surgery is the first treatment. The surgeon tries to remove as much of the tumor as possible. In high-risk areas of the brain, it may not be possible to remove all of it.

Radiation is used to kill as many leftover tumor cells as possible after surgery. It can also slow the growth of tumors that can't be removed by surgery.

Chemotherapy may also help. Temozolomide is the most common chemotherapy drug doctors use for glioblastoma. Carmustine (BCNU) and lomustine (CCNU) are other chemotherapy drugs that might be used.

Targeted therapy with the drug bevacizumab (Avastin, Mvasi) may be given if chemotherapy has not been effective.

Convection-enhanced delivery (CED) uses a pump to release a slow, continuous stream of chemotherapy or targeted therapies to a tumor.

Electric field therapy uses electrical fields to target cells in the tumor while not hurting normal cells. To do this, doctors put electrodes directly on the scalp. The device is called Optune. You get it with chemotherapy after surgery and radiation. The FDA has approved it for both newly diagnosed people and people whose glioblastoma has come back.

Wafer therapy (Gliadel) uses an implanted, biodegradable disc that releases chemotherapy to any cancerous tissue that is left after surgery.

Nanoparticle therapy uses tiny particles to carry chemotherapy directly into the tumor.

At major cancer centers, you may also be able to get experimental treatments or oral chemotherapy, which you take at home.

These treatments may help with symptoms and possibly put the cancer into remission in some people. In remission, symptoms may let up or disappear for a time.

Glioblastomas often regrow. If that happens, doctors may be able to treat it with surgery and a different form of radiation and chemotherapy.

Palliative care is also important for anyone with a serious illness. It includes taking care of your pain and the emotions you may be dealing with, as well as other symptoms from your cancer. The goal is to improve the quality of your life.

You may also want to ask your doctor if there’s a clinical trial that would be a good fit for you.

Outlook and Survival Rates

Many things can affect how well someone does when they have cancer, including glioblastomas. Doctors often can’t predict what someone’s life expectancy will be if they have a glioblastoma. But they do have statistics that track how large groups of people who’ve had these conditions tend to do over time.

For glioblastoma, the survival rates are:

  • One year: 25%
  • Two years: 8-12%
  • Five years: 5%

These numbers can’t predict what will happen to an individual, though. A person’s age, type of tumor, and overall health play a role. As treatments improve, people newly diagnosed with these aggressive brain tumors may have a better outcome.

Glioma vs. Glioblastoma

Glioma is one the most common types of primary brain cancer. It’s an umbrella term for tumors that develop from glue-like cells known as glial cells that surround nerve cells in your brain or spinal cord.

Glioblastoma is a type of glioma. All advanced forms of glioma, also known as grade 4 glioma, are called glioblastoma, the most aggressive type of glioma.

Show Sources

SOURCES:

American Association of Neurological Surgeons: "Glioblastoma Multiforme."

American Brain Tumor Association: "Glioblastoma," "Brain Tumor Primer," "Glioblastoma and Malignant Astrocytoma."

CBTRUS Statistical Report: “Primary Brain and Other Central Nervous System Tumors Diagnosed in the United States in 2009-2013.”

Clinical Cancer Research: “The definition of primary and secondary glioblastoma.”

Frontiers in Oncology: “Genetics and Epigenetics of Glioblastoma: Applications and Overall Incidence of IDH1 Mutation.”

Massachusetts General Hospital Brain Tumor Center: "Therapeutic Door Opens for Aggressive Brain Cancer."

Mayo Clinic: “Glioma.”

MD Anderson Cancer Center: “Glioblastoma,” “Q&A: Understanding glioblastoma (GBM),” Glioma vs. glioblastoma: What’s the difference?”

Moffitt Cancer Center: “Glioblastoma Causes,” “Glioblastoma Stages.”

National Organization for Rare Disorders: “Glioblastoma.”

Roswell Park Comprehensive Cancer Center: “Glioma vs. glioblastoma: What’s the difference?”

University of California, San Diego Neurosurgery: "Glioblastoma."

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