Malignant Glioma

Malignant gliomas are rapidly progressive brain tumors that grow quickly and can invade healthy brain tissue, making them among the most serious types of brain cancer with very high rates of illness and death.

Table of contents

• What is Malignant Glioma?
• Types of Malignant Gliomas
• Who is Affected?
• Signs and Symptoms
• Causes and Risk Factors
• How Doctors Diagnose Malignant Gliomas
• Treatment Approaches
• Outlook and Survival

What is Malignant Glioma?

A malignant glioma is a cancerous tumor that forms in the brain or spinal cord. These tumors develop from glial cells, which are supporting cells that normally help nerve cells in the brain and spinal cord function properly. Glial cells surround nerve cells and provide them with protection, food, and oxygen^[1].

When glial cells grow out of control, they can form tumors. Malignant gliomas are considered high-grade tumors, meaning they grow rapidly and are very aggressive^[3]. Unlike many other cancers, these tumors do not typically spread to other parts of the body outside the brain and spinal cord. However, they can invade and spread to different areas within the brain itself^[2].

• Brain
• Spinal cord
• Central nervous system

Types of Malignant Gliomas

Malignant gliomas include several different types of brain tumors. These are classified as grade III or grade IV tumors by the World Health Organization (WHO), which is a system doctors use to categorize how serious the tumor is^[3].

The main types of malignant gliomas include:

• Glioblastoma (grade IV): This is the most aggressive and most common type of malignant glioma. Glioblastomas account for approximately 60 to 70% of all malignant gliomas^[3]. They are fast-growing tumors that can invade nearby regions of the brain^[7].
• Anaplastic astrocytoma (grade III): These tumors represent 10 to 15% of malignant gliomas. They develop from star-shaped brain cells called astrocytes^[3].
• Anaplastic oligodendroglioma (grade III): These tumors develop from glial cells called oligodendrocytes and account for about 10% of malignant gliomas^[3].
• Mixed anaplastic oligoastrocytoma (grade III): These contain features of both oligodendroglioma and astrocytoma^[3].

Doctors now also look for specific genetic changes in tumor cells, such as mutations in the IDH gene, to help classify the tumor type more precisely. This information helps predict how the tumor might behave and guides treatment decisions^[6].

Who is Affected?

Malignant gliomas can affect people of all ages, but they are more common in adults. The rate of occurrence is approximately 5 out of every 100,000 people^[3]. These tumors make up 35 to 45% of all primary brain tumors, which are tumors that start in the brain rather than spreading from elsewhere in the body^[3].

The peak age for developing malignant gliomas is in the fifth and sixth decades of life, meaning most people are diagnosed between ages 50 and 70. For glioblastoma specifically, the median age at diagnosis is 64 years. For other types of malignant gliomas called anaplastic gliomas, the median age is younger, around 45 years^[3].

These tumors are 40% more common in men than in women. They also occur twice as often in white populations compared to Black populations^[3]. The incidence has increased slightly over the past two decades, especially in elderly people^[3].

Signs and Symptoms

The symptoms of malignant glioma depend on where the tumor is located in the brain and how large it has grown. Because these tumors grow quickly, symptoms may appear suddenly or worsen rapidly^[1].

Common signs and symptoms include:

• Severe headaches, particularly those that hurt most in the morning^[1]
• Nausea and vomiting^[1]
• Seizures or convulsions^[2]
• Confusion or problems with thinking and understanding information^[1]
• Memory loss^[1]
• Personality changes or irritability^[1]
• Vision problems, such as blurred or double vision^[1]
• Difficulty speaking or understanding others^[2]
• Weakness or numbness on one side of the body^[2]
• Difficulty walking or keeping balance^[2]
• Dizziness^[2]

If you experience any of these symptoms, it is important to see a doctor as soon as possible. Early detection can lead to more effective treatment^[2].

Causes and Risk Factors

The exact cause of malignant gliomas is not fully understood. These tumors develop when genetic changes occur in glial cells, causing them to grow out of control. Doctors do not always know why these genetic changes happen^[2].

The only clearly established environmental risk factor for most malignant gliomas is exposure to ionizing radiation, which is a type of high-energy radiation^[3].

Several factors may increase a person’s risk of developing malignant gliomas:

• Age: These tumors are most common in adults over age 65 and in children before age 12^[2].
• Family history: Some genetic disorders that run in families may increase risk. If brain or spinal cord tumors run in your biological family, you may want to consider genetic testing and counseling^[2].
• Race: People who are white may be more likely to develop gliomas than people of other races^[2].
• Radiation exposure: Repeated exposure to radiation or certain chemicals may increase risk^[2].

There is some evidence that factors related to the immune system may play a role. For example, patients with certain allergic conditions appear to have a reduced risk of gliomas, and patients with glioblastoma who have elevated levels of a specific immune protein called IgE appear to live longer than those with normal levels^[3].

Most people who develop malignant gliomas do not have clear risk factors, so you should not worry excessively about prevention^[2].

How Doctors Diagnose Malignant Gliomas

Diagnosing a malignant glioma involves several steps and different types of tests. Your doctor will begin with a physical examination and then order specific tests to look at your brain^[9].

Neurological examination: This exam checks your vision, hearing, balance, coordination, strength, and reflexes. Difficulty with certain tasks might suggest a brain tumor^[9].

Imaging tests: These tests create pictures of your brain to look for signs of a tumor. The most commonly used imaging test is Magnetic Resonance Imaging (MRI). Sometimes a dye is injected into a vein before the MRI to create better pictures. Other imaging tests may include CT scans (computed tomography) and PET scans (positron emission tomography)^[9].

Biopsy: This is a procedure to remove a small sample of tissue for testing. Sometimes a biopsy is done before treatment begins, especially when surgery is not an option for removing the tumor. During a stereotactic needle biopsy, a small hole is made in the skull, and a thin needle is inserted through the hole to remove tissue. This tissue is then sent to a laboratory for testing^[9].

If surgery is planned to remove the tumor, the tissue sample can be taken during that surgery rather than in a separate biopsy procedure^[9].

Laboratory tests on tumor cells: Doctors who specialize in analyzing tissue examine the tumor sample under a microscope. They look at the type of cells, how abnormal they appear, and whether they contain specific genetic changes. These tests help determine the exact type of glioma and guide treatment decisions^[9].

Treatment Approaches

Treatment for malignant gliomas requires a team approach involving different types of doctors, including neurosurgeons, oncologists, and radiation specialists. The goal is to remove or destroy as much of the tumor as possible while preserving brain function^[3].

Surgery: The first step in treating malignant gliomas is usually surgery to remove as much of the tumor as possible. This is called gross total resection. Surgery can remove about 95 to 98% of the visible tumor, but some microscopic disease often remains that cannot be seen on imaging scans^[14]. Studies show that people who undergo complete or near-complete tumor removal tend to have better outcomes^[13].

Radiation therapy: After surgery, patients typically receive radiation therapy to the area where the tumor was removed and the surrounding brain tissue. This treatment is usually given over about six weeks at a total dose of 6000 to 6500 cGy. Radiation therapy has been shown to improve survival rates^[13].

Chemotherapy: Chemotherapy involves using drugs to kill cancer cells. For malignant gliomas, chemotherapy is often given at the same time as radiation therapy. The most commonly used drug is called temozolomide, which is taken by mouth. Other chemotherapy drugs that may be used include carmustine (BCNU) or a combination of drugs called PCV-3, which includes procarbazine, lomustine (CCNU), and vincristine^[13].

Chemotherapy has been shown to improve survival in approximately one-quarter of patients with glioblastoma and in the majority of patients with anaplastic astrocytoma. However, doctors cannot predict in advance which patients will benefit most from chemotherapy, so it is typically offered to all patients who are relatively young with good overall health^[13].

The treatment approach is individualized based on each patient’s specific situation, including the type of tumor, its location, the patient’s age, and overall health^[3].

Outlook and Survival

Malignant gliomas are serious tumors with very high rates of illness and death^[3]. The outlook depends on several factors, including the type of glioma, the patient’s age, overall health, and how much of the tumor can be removed.

For glioblastoma, which is the most aggressive type, the median survival ranges from 9 to 12 months despite maximum treatment efforts. This statistic has changed little over several decades^[5]. The average survival for malignant gliomas in general ranges from 7.8 to 23.4 months after diagnosis^[18].

However, it is important to understand that these are average numbers, and individual outcomes can vary significantly. Some people with certain types of malignant gliomas, particularly those with specific genetic features, may live longer^[3].

Treatment can help extend survival and improve quality of life. New treatments, such as tumor-treating fields and targeted drugs that work against specific genetic changes in tumors, have shown promise in extending life expectancy by several months^[18].

Living with a malignant glioma presents many challenges. These tumors and their treatments can cause cognitive changes, including difficulty concentrating, learning, and remembering new things. These effects can significantly impact a person’s quality of life and ability to work and maintain relationships^[3].

Support services, including rehabilitation, counseling, and help with practical matters such as disability and insurance, are important parts of comprehensive care^[3]. Your healthcare team can help you understand what to expect and connect you with resources to support you and your family.