What Is Glioblastoma?

Overview

Glioblastoma is an aggressive cancerous brain tumor that starts in the brain.
Glioblastoma is an aggressive cancerous brain tumor that starts in the brain.

Glioblastoma is a type of cancerous brain tumor. It’s the most common “primary” brain cancer. That means it starts in the brain rather than spreading to the brain from somewhere else.

Doctors diagnose 12,000 new glioblastoma cases in the U.S. each year. All glioblastomas are “grade IV” cancers. That is the fastest growing and most aggressive type of cancer.

Glioblastomas usually show up in the brain. But they can also appear in the spinal cord.

What Is a Glioblastoma?

Cancer starts in abnormal cells. These abnormal cells can form lumps or clusters known as tumors.

In the case of glioblastoma, the tumor starts in brain cells called astrocytes. Like the name suggests, they are star-shaped cells. These cells form the walls that keep infections and other substances in the blood from reaching the brain. They also help supply the brain with nutrients.

Why Do Glioblastomas Form?

Experts aren’t sure what causes glioblastomas. There’s some evidence that genetic mutations cause astrocytes in the brain to multiply and form tumors. But there’s a lot that doctors don’t understand about how glioblastomas start.

Types of Glioblastoma

All glioblastoma tumors fall into one of two categories:

  • De novo tumors are aggressive, grade IV cancers right from the start.
  • Secondary tumors are glioblastomas that started as other lower-grade tumors in the brain cells.

Doctors also categorize glioblastoma by genetic makeup:

  • IDH-Wildtype are tumors that have a variety of abnormal genes.
  • IDH-Mutant are tumors that contain genes with known mutations.

These differences help doctors decide how to treat the tumor.

Symptoms of Glioblastoma

Symptoms of glioblastoma tend to start out mild and get worse over time. They include:

Who Is at Risk for Glioblastoma?

Men are a little more likely than women to develop a glioblastoma. The cancer can turn up at any age, but it usually develops in people age 50 and older. Most people are around 64 when they find out they have a glioblastoma.

Doctors think glioblastomas show up “randomly.” That means they’re not something you inherit from a relative via your DNA. There’s some evidence that people who have allergies are less likely to develop a glioblastoma, but doctors aren’t sure why.

High levels of ionizing radiation can increase your glioblastoma risks. This is the kind of radiation doctors use for cancer treatment.

How Do Doctors Diagnose a Glioblastoma?

If your doctor thinks you could have a glioblastoma, he or she will likely refer you to a neurologist. A neurologist is a brain specialist.

A neurologist diagnoses glioblastomas using:

  • A neurological exam: The doctor checks your hearing, vision, balance, and other clues about how your brain is working.
  • Imaging tests: MRIs, CT scans, and other pictures of your brain can help your doctor spot a glioblastoma.
  • Biopsy: Your doctor removes tissue samples from your tumor to better understand and know how to treat your tumor.
  • Genetic testing: Your doctor will examine the genetic material inside your tumor cells to know which treatments might work best.

How Do Doctors Treat Glioblastoma?

Doctors usually treat glioblastoma with:

  • Surgery as soon as possible to remove as much of the tumor as possible
  • Combination therapy that includes chemotherapy and radiation
  • Chemotherapy by itself after combination therapy

Some older people or people who have advanced tumors might not do well in surgery. Chemotherapy and radiation therapy might still be good options for people who can’t have surgery.

What’s the Prognosis After Treatment?

Glioblastoma is an aggressive and often deadly type of cancer. The average person lives for 11 to 15 months after treatment.

People who develop glioblastoma before age 50 may live longer. The same is true if a doctor is able to remove all of the tumor during surgery.

Also, people with the IDH-mutant form of glioblastoma tend to live longer after treatment. Their tumors sometimes respond better to certain types of chemotherapy drugs. Their average survival time is 27 to 31 months.

References
(c)2019 WebMD, LLC. All rights reserved.

MD Anderson Cancer Center: “Glioblastoma.”

Mayo Clinic: “Glioblastoma.”

Cedar Sinai: “Glioblastoma multiforme.”

American Brain Tumor Association. “Glioblastoma (GBM).”
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