What is a Glioma: Understanding Types & Standard of Care

So essentially, a glioma is a tumor that comes from the brain’s own support cells.

“Glioma is a broad term that refers to a whole range of different types of primary brain tumors,” Dr. Alexandra Miller, Director of the Neuro-Oncologist Division at NYU Langone Health, tells SurvivorNet. “So, they’re tumors that originate in the brain and very rarely spread outside the brain to other parts of the body.”

Those glial cells, like many other cells in the body, have the potential to grow abnormally and form a mass, and that is when a glioma is formed. Gliomas, as they arise from the brain or spinal cord, are considered a primary brain tumor. They do not spread from elsewhere in the body. Relative to other cancers such as breast, prostate, and lung, primary brain tumors are relatively uncommon with 80,000 diagnosed per year in the United States. Of the primary brain tumors diagnosed each year, gliomas comprise approximately 25%.

Gliomas: Benign vs. Malignant

To answer this question it is important to understand what it means for a tumor to be cancerous versus benign. A benign tumor often grows slowly and has clear borders, meaning it does not invade into surrounding tissue or other parts of the body. Meanwhile when something is described as cancerous or malignant it often grows more quickly and has a propensity to invade into surrounding tissue and spread to other sites of the body.

That being said, gliomas can vary widely in their behavior, meaning some are benign while others are considered malignant or cancers. Whether a glioma is benign or malignant depends on several factors including its type and grade.

Glioma is a general term that describes several different types of tumors. The different types of glioma depends on which specific glial cell is involved. Examples include:

• Astrocytomas – Gliomas originating from astrocytes, a type of glial cell that maintains the chemical environment around neurons and provides nourishment
• Oligodendrogliomas – Gliomas from oligodendrocytes, which are glial cells that create the myelin sheath that insulates nerve fibers and make neurons transfer signals more quickly and efficiently
• Ependymomas – Gliomas that from ependymal cells, which are cells that line the cavities of the brain and spinal cord and produce cerebrospinal fluid

Each of these types of gliomas behaves differently and can be considered more or less malignant or aggressive. Each type of glioma is typically classified further by their grade, which is a measure of how aggressive the tumor is.

The Grading System of Gliomas

Gliomas are graded on a scale of I to IV, with higher grades indicating a more aggressive tumor. This grading is based on several factors including the type of glioma, the genetics of the cancer, as well as the appearance of the tumor cells under a microscope. The more abnormal the cells look, the higher the grade, and the faster the tumor is likely to grow and spread. Here’s a quick overview:

• Grade I-II gliomas – These are considered low-grade and tend to grow slowly. “The grade one is a very indolent, benign tumor that basically can be cured with surgery alone,” Dr. Henry Friedman, Deputy Director of the Preston Robert Tisch Brain Tumor Center at Duke, tells SurvivorNet.
• Grade III gliomas – These are considered high-grade and tend to grow more rapidly. Grade III gliomas are typically classified as malignant and typically require more aggressive treatment which can include surgery, radiation, and chemotherapy.
• Grade IV gliomas – These are the most aggressive gliomas which are locally aggressive and require treatment intensification. Glioblastomas are the most common grade IV glioma, “which is by far the most well known and most feared tumor in the lay population and quite frankly, the medical population as well,” Dr. Friedman explains.

Although Grade IV gliomas are the most aggressive glioma and may require several types of treatment including surgery, radiation, and chemotherapy, there can be challenges in treating low grade gliomas as well. When making decisions on treatment, several factors are taken into consideration including location of the tumor, ease of surgery and ability to resect, neurologic deficits, patient age, tumor size, and overall health.

How Does Glioma Present?

Gliomas can present a variety of ways. The symptoms are often non-specific, meaning there is no slam-dunk symptom or key finding that is common to all gliomas. Symptoms can also be related to tumor location, and more commonly the increased pressure caused by the mass inside the skull, which can disrupt blood flow and block the flow of cerebral spinal fluid. Based on the location of the glioma there can be associated symptoms that arise including personality and speech changes.

With increased pressure in the skull you can experience symptoms such as headaches, nausea, vomiting, and changes in vision.

Other symptoms that can sometimes be seen include:

• Seizures
• Cognitive difficulties, like memory loss or trouble concentrating
• Weakness or numbness in certain parts of the body
• Vision or speech problems

Again, none of these symptoms are specific to gliomas and can be caused by a variety of medical conditions. There are several steps in the workup needed before you can be diagnosed with a glioma.

Diagnosis and Imaging

Often patients present with non-specific symptoms as described above to their primary care doctor, an urgent care, or an emergency room. If there is concern for a glioma or primary brain tumor, several tests will be performed which typically include:

• A thorough history and neurologic exam
• Blood tests which look at total blood counts (CBC) and metabolic markers (CMP)
• Brain MRI

The MRI allows doctors to obtain the most detailed images of the brain and clarify the size, shape, and location of a suspected glioma. Although MRIs are great for gathering information and helping the medical team create a potential surgical plan, a biopsy is required in order to confirm the diagnosis of glioma and also provide specific information including the type of glioma of grade.

Biopsy

During a biopsy, a sample of the tumor is taken and examined under a microscope.

A biopsy is a surgical procedure, but it can be done in different ways. Sometimes it’s performed as part of a larger surgery to remove the tumor, or it can be done separately as a stereotactic biopsy, which is minimally invasive. Advanced imaging techniques are used to guide the biopsy so a sample can be safely obtained.

According to Dr. Friedman, when making a diagnosis of glioma, this “includes looking at it under the microscope through our pathology team. Everybody’s doing next generation sequencing now to really get an idea of the molecular composition of the tumor. And with that information we can then see if they fit into a clinical trial paradigm and if they do, terrific. If not, there is standard of care.”

This means that sometimes based on the testing performed on biopsy specimens, patients can be eligible for clinical trials testing new forms of therapy based on mutations and changes specific to the tumor. Additionally patients could also be considered for certain FDA approved therapies (i.e. BRAF/MEK inhibitors, NTRK fusion inhibitors, and pembrolizumab if TMB-high).

Treatment Options

“The first step is always the neurosurgery. How much can you take out? Is it safe to do surgery? Do you have to rely on a biopsy? Can you even do a biopsy?” says Dr. Friedman. These are all questions and considerations that need to accounted for when deciding what treatment is most appropriate.

Once the biopsy is obtained and the diagnosis of glioma is made, various treatment options can be recommended. The recommendations take into account the type of the glioma, the tumor grade, and well as patient specific factors including tumor location, size, your age, and overall health.

The main treatment options are:

• Observation – Some gliomas that are benign, small, and without symptoms or tumors located in inoperable locations can be recommended for observation.
• Surgery – Surgery is often the first-line treatment for gliomas, with the goal of achieving maximal safe resection where the largest amount of tumor is removed without causing significant neurologic deficits. For low-grade gliomas, surgery alone can sometimes be curative.
• Radiation therapy – This uses high-energy x-rays to target and kill tumor cells. Radiation is often used after surgery to target residual tumor cells.
• Chemotherapy – These medications kill or slow the growth of cancer cells. Chemotherapy can be used alongside radiation, or following radiation and is often used in higher-grade tumors.
• Targeted therapy and immunotherapy – These are newer treatments that are designed to target specific genetic mutations in the tumor or to stimulate the immune system to fight the cancer. Their role in the treatment for gliomas is continuing to evolve.

The important thing to remember is that every treatment plan and recommendation made by your healthcare team is personalized based off of details specific to your disease, your overall health, and treatment goals.

Living with a Glioma

Low-grade gliomas can sometimes be cured, but they may come back, which is why it is important to be monitored closely with regular examinations and imaging.

“Gliomas are unique tumors in that they’re very infiltrative tumors,” Dr. Miller adds. “So it’s almost like if you throw up a handful of sand, you can never pick up every grain of sand. We know that there are always tumor cells that are scattered beyond the margins we can see on an MRI. Even if a best case scenario where a surgeon can take out the majority of the tumor, we know that there are residual cells that are there that have to be monitored over time.”

In higher-grade gliomas, like glioblastomas, the follow up and post-treatment course can present more of a challenge as they can often recur. The important thing to consider is that the decision to provide treatment is always made with the goal of providing the best possible outcome while also managing symptoms and side effects.

Learn more about SurvivorNet's rigorous medical review process.

---