What Are the Causes of Glioma?

Are you wondering about the causes of gliomas? For many people, it is difficult to imagine a seemingly healthy person developing brain cancer. Unfortunately, it is often hard to pinpoint a clear cause for gliomas.

Gliomas are believed to arise from genetic mutations (changes) of glial cells. When the genetic makeup of these cells becomes mutated, abnormal tissue growth can lead to tumors such as glioma and glioblastoma. These mutations are not fully understood; however, we have identified potential causes and risk factors, such as exposure to ionizing radiation and hereditary genetic conditions. 

What is a mutation? What causes ionizing radiation? Can you inherit glioblastoma? These are important questions. Below, we will walk through several answers. 

Though the cause of glioma is not fully understood, scientists and physicians have several strong theories. Below, we will explore the two most common potential causes of gliomas:

1. Exposure to ionizing radiation
2. Genetic and hereditary conditions

In later sections, we will provide an overview of the cellular mutations that lead to gliomas. While these mutations are not necessarily the primary cause, learning about the formation of gliomas can reduce confusion about the disease. 

Ionizing radiation produces energy capable of stripping electrons from atoms. Exposure to sufficient amounts of ionizing radiation can lead to mutations that may induce the formation of cancerous cells. 

What types of things produce ionizing radiation? The most common place a person would encounter ionizing radiation is X-rays and CT scans (MRIs do not produce radiation) or when undergoing radiation therapy to treat other diseases. However, something (though uncommon) like an atomic blast could also release ionizing radiation. 

Most physicians carefully weigh the benefits of diagnoses and treatment against the potential for adverse effects from medical procedures that produce ionizing radiation. 

In addition to ionizing radiation, many believe genetics play a role in causing brain tumors. We address the possibility of inheriting glioma in the next section. 

Can someone inherit glioma or glioblastoma from their parents or relatives? Physicians do consider a family history of glioma or glioblastoma a risk factor for brain tumors. However, many patients develop glioma or glioblastoma with no apparent family link. 

Below are rare genetic conditions that may increase the likelihood of developing tumors in general, including those that arise in the brain:

1. Turcot Syndrome: Mutations in DNA repair genes (MLH1 and PMS2) or a tumor suppressor gene (APC) that may initially manifest with tumors in the colon. 
2. Neurofibromatosis type 1: Mutation in the NF1 gene that normally inhibits cell growth. Characterized by small tumors along the nerves.
3. Li-Fraumeni syndrome: Mutation in the TP53 gene that usually prevents tumors. Increases the risk of many cancers.

These are rare conditions and only serve to illustrate risk factors at a cellular level. In the next section, we will talk about how gliomas emerge from mutations. 

The reasons why mutations occur are not fully understood. However, once sufficient amounts of cellular mutations take place, the cells may progress to become cancerous and be able to undergo uncontrollable growth. At this point, you might wonder: What is a mutation? And how does it form into glioblastoma? Below, we offer a basic explanation. 

Glial cells (the support cells in the brain) have a life of their own - they form, do their jobs, and are replenished when they fail to work properly. However, if a mutation occurs, it can disrupt the glial cell life cycle. These cells can begin multiplying without limit. This rapid, uncontrolled growth is what leads to a tumor. 

However, not all tumors are as invasive as others. In the next section, we will discuss what might cause invasive, high-grade gliomas. 

What is a high-grade glioma? Gliomas fall within four grades. Grade one is the least invasive, and grade four is the most invasive. Glioblastoma is a grade-four glioma. As such, it typically carries a very poor prognosis. 

The cause of a high-grade glioma is often a low-grade glioma that returns after it has been surgically removed or that continues to expand and evolve over time. It is also possible for high-grade gliomas to arise sporadically or spontaneously. Nevertheless, an especially aggressive glioma expands rapidly, with some even growing self-sustaining blood vessels. Thus, detecting and treating gliomas while they are in the lower grade is important to prolong survival. In the next section, we will discuss a common question for patients with glioma: Is a low-grade glioma curable?

Low-grade gliomas (grades one and two), when diagnosed and treated properly, have the best survival rates. Low-grade gliomas are relatively benign tumors. Neurosurgeons often treat these gliomas with surgery, but these tumors are not curable. In many cases, low-grade gliomas have a greater than 90% survival rate within 7 years after the diagnosis. Unfortunately, almost all low-grade gliomas transform to their high-grade counterparts and shorten the lifespan of the patient.

The causes of glioma are not fully understood. Ionizing radiation and several rare genetic conditions are two potential causes. Low-grade gliomas are likely to progress to high-grade gliomas. Early treatment of low-grade glioma is key to long-term survival.

There is much information from various sources about the cause of gliomas and glioblastomas. Be careful to consult with trusted physicians as you draw conclusions about what causes gliomas. In many cases, it appears that brain tumors are the result of random spontaneous mutations. 

• Glioblastoma Foundation
• Centers for Disease Control and Prevention
• Brain Tumor Foundation