Glioma

Glioma is a type of tumor that develops in the brain or spinal cord from the support cells that help nerve cells function properly. These tumors can grow at different speeds and vary greatly in their seriousness, from slow-growing forms that may be manageable for years to aggressive types that require urgent and intensive treatment.

Table of contents

• What is glioma?
• Types of glioma
• Symptoms
• Causes and risk factors
• Diagnosis
• Treatment options
• Glioma grading
• Outlook and survival

What is glioma?

A glioma is a tumor that forms when the body’s glial cells grow out of control^[2]. Glial cells are support cells in the brain and spinal cord that surround nerve cells and help them work properly^[1]. These cells have important roles in keeping the central nervous system (the brain and spinal cord) functioning^[2].

Gliomas are primary tumors, which means they form directly in the brain or spinal cord rather than spreading from another part of the body^[2]. They are the most common type of primary brain tumor in adults^[3]. In the United States, about 6 cases of gliomas are diagnosed per 100,000 people every year^[3].

As a glioma grows, it forms a mass of cells. The tumor can press on brain or spinal cord tissue and cause various symptoms depending on which part is affected^[1]. Some gliomas grow slowly and are not considered cancerous, while others grow quickly and are malignant (cancerous)^[1].

• Brain
• Spinal cord
• Central nervous system

Types of glioma

Gliomas are classified based on the type of glial cell they develop from and how quickly they grow^[2]. There are three common types of gliomas based on the cell of origin: astrocytomas, ependymomas, and oligodendrogliomas^[3].

Astrocytomas are the most common type of glioma^[5]. They develop from star-shaped brain cells called astrocytes and can range from slow-growing (low-grade) to aggressive (high-grade)^[2]. All astrocytomas are now described as astrocytoma, IDH mutant, and are classified into grades 2, 3, or 4 based on how quickly they are likely to grow^[5].

Oligodendrogliomas are rare gliomas that develop from glial cells called oligodendrocytes^[5]. These are usually low-grade gliomas that affect adults more than children^[2]. They are described as oligodendroglioma, IDH mutant, and 1p/19q codeleted, and can be grade 2 or grade 3^[5].

Ependymomas develop from cells called ependymocytes, which line the cavities of the brain and spinal canal^[3]. These tumors are rare and affect children more than adults^[2]. They are usually low-grade gliomas^[2].

Glioblastoma (WHO grade 4) is the most aggressive type of glioma and is considered a distinct diagnosis^[2]. It is the most common type of malignant brain tumor in adults^[2]. Glioblastomas are described as glioblastoma, IDH wildtype, and all are classified as grade 4^[5].

Tumors that contain a mixture of more than one type of glial cell are called mixed gliomas or oligoastrocytomas^[6]. Some gliomas are named based on their location in the brain, such as optic nerve glioma (affecting the optic nerves) or brain stem glioma (in the brainstem)^[6].

Symptoms

Glioma symptoms depend on where the tumor is located in the brain or spinal cord^[1]. They also depend on the type of glioma, its size, and how fast it is growing^[1]. The symptoms arise as a result of increased pressure inside the skull or damage to specific parts of the brain^[8].

Common symptoms of gliomas include^[1][2]:

• Headaches, particularly ones that hurt the most in the morning
• Nausea and vomiting
• Confusion or problems with thinking and understanding information
• Memory loss
• Personality changes or irritability
• Vision problems, such as blurred vision or sudden vision loss
• Difficulty walking or keeping balance
• Dizziness
• Seizures
• New depression or anxiety
• Sudden mood swings
• Trouble speaking or communicating
• Weakness or numbness on one side of the body

When a glioma affects the optic nerve, it can cause vision loss and other problems with eyesight^[8]. Spinal cord gliomas can cause pain, weakness, or numbness in the arms, legs, hands, or feet^[8].

Causes and risk factors

Genetic changes in glial cells cause gliomas, but doctors do not always know why these changes occur^[2]. The exact causes of gliomas are not fully understood^[8].

Certain factors may increase the risk of developing a glioma^[2]:

• Age: Gliomas are most common in adults after age 65 and in children before age 12^[2].
• Hereditary disorders: Some genetic disorders that can be inherited from biological family members may increase risk, such as neurofibromatosis and tuberous sclerosis complex^[8].
• Radiation exposure: The best-known risk factor is exposure to ionizing radiation, including radiation from medical imaging tests^[8]. Repeated exposure to radiation or certain chemicals may increase risk^[2].
• Race: People who are white may be more likely to develop gliomas than other races^[2].
• Family history: Some genetic disorders inherited from biological family can increase the risk of brain or spinal cord tumors^[2].

Most gliomas are not linked to clear risk factors, and you cannot prevent them^[2]. However, staying informed and seeking care early if you notice symptoms may improve outcomes^[2].

Diagnosis

Diagnosing a glioma usually starts with a physical examination and a neurological exam to check how the brain and nerves are working^[9]. This exam involves checking vision, hearing, balance, coordination, strength, and reflexes^[9].

If a doctor suspects a glioma, the next step is usually imaging tests to create pictures of the brain^[9]. Magnetic resonance imaging (MRI) is the imaging test used most often to look for signs of a brain tumor^[9]. Sometimes a dye is injected into a vein before the MRI to help create better pictures^[9]. Other imaging tests may include computed tomography (CT) scans or positron emission tomography (PET) scans^[9].

A procedure called a biopsy may be needed to remove some tissue for testing^[9]. During this procedure, a needle is guided by imaging tests to remove a small sample of the tumor through a small hole in the skull^[9]. If surgery to remove the tumor is planned, a separate biopsy before surgery may not be needed^[9].

The tissue sample is sent to a laboratory where specialists examine it closely^[9]. They look at the type of glial cells, changes to genes and proteins in the cells (such as the IDH gene), and how normal or abnormal the tumor cells look^[5]. These tests help determine the exact type of glioma and how it should be treated^[9].

Treatment options

Glioma treatment requires a team approach involving different specialists^[16]. The treatment plan will be tailored to each patient’s needs and preferences and may include surgery, radiation therapy, chemotherapy, and other approaches^[1][2].

Surgery is often the first step in treatment when the tumor can be safely removed^[13]. The goal is to remove as much of the tumor as possible^[13]. This procedure is called a resection and can be total or partial^[13]. Surgery helps reduce pressure in the brain, stop the tumor from growing, and relieve symptoms^[13].

Radiation therapy uses rays to destroy cancer cells^[13]. It is often used after surgery to kill remaining cancer cells^[13]. Radiation therapy is a standard part of treatment for many types of gliomas^[16].

Chemotherapy uses medicines to kill cancer cells or slow their growth^[1]. For gliomas, chemotherapy can be given as pills taken by mouth or as infusions into a vein^[13]. It is often used after surgery to kill remaining cancer cells^[13].

In some cases, an observation period or “watch and wait” approach may be recommended^[13]. This gives patients and doctors more time to evaluate the disease and may reduce the time experiencing side effects from treatment^[13].

Targeted treatment may be available if a glioma has a specific mutation. These treatments directly target what is causing the tumor to grow^[13]. Recent research has shown promise for new targeted therapies, such as the drug avapritinib for tumors with changes in the PDGFRA gene^[15].

Clinical trials test new treatments that are not yet available to the general public^[13]. Health organizations recommend that people with glioma look into available clinical trials as a treatment option^[13].

The choice of treatment depends on various factors, including the grade and location of the glioma, overall health, and whether the tumor can be removed by surgery^[13]. For most gliomas, treatment involves a combination of surgery, radiation, and chemotherapy^[13].

Glioma grading

Healthcare providers grade gliomas to understand how quickly they grow and how serious they are^[2]. The grade is based on how fast the tumor grows, how abnormal the cells look, and how likely it is to spread^[2].

The World Health Organization (WHO) grading system uses four grades, ranging from grade 1 (the slowest growing) to grade 4 (the most aggressive and fastest growing)^[2]. Grades are also grouped together as low-grade (grades 1 and 2) or high-grade (grades 3 and 4)^[2].

Low-grade gliomas (grades 1 and 2) grow and spread slowly^[13]. High-grade gliomas (grades 3 and 4) grow and spread quickly^[13]. Early detection and treatment of low-grade gliomas may slow or prevent them from becoming high-grade^[2].

The WHO classification has recently changed to include molecular information as the primary evidence for classifying and grading gliomas^[16]. Important molecular factors include whether there are changes (mutations) in the IDH gene and whether there is a 1p/19q codeletion^[5]. These molecular markers help predict how the tumor will behave and guide treatment decisions^[3].

Outlook and survival

The outlook for people with gliomas varies greatly depending on the type of glioma and other factors^[12]. Some gliomas can be controlled for many years, while others are more aggressive^[12].

Important factors that affect survival include younger age and better overall health at diagnosis^[3]. Molecular genetic factors, especially IDH mutation and 1p/19q codeletion, have significant value in predicting outcomes^[3].

Low-grade gliomas typically have a longer survival time, with a median of 5 to 7 years^[16]. High-grade gliomas, particularly glioblastoma (IDH-wildtype), have a poorer outlook with a median survival of 12 to 18 months^[16].

Follow-up care is essential for anyone with glioma^[21]. Follow-up appointments, including brain scans, are a vital part of the treatment plan^[21]. Working with the healthcare team to follow the recommended appointment schedule as closely as possible is important^[21].

Recent advances in treatment, including newer chemotherapy approaches and targeted therapies, have led to some improvements in survival^[12]. Standard treatment with surgery followed by radiation and chemotherapy has become the established approach for many types of gliomas^[12].