Glioma is a broad category of brain and spinal cord tumors that come from glial cells brain cells that support nerve cells.
The symptoms, prognosis, and treatment of a glioma depend on the person’s age, the exact type of tumor, and the location of the tumor within the brain. These tumors tend to grow and infiltrate into the normal brain tissue, which makes surgical removal very difficult -- or sometimes impossible -- and complicates treatment.
These brain tumors are often diagnosed older adults , depending on the type of glioma. Brain tumors are slightly more likely to occur in males. Most gliomas that occur in children are low grade.
Prior radiation to the brain is a risk factor for malignant gliomas. Some genetic disorders also increase the risk of development of these tumors in children but rarely in adults.
There are no lifestyle risk factors associated with malignant gliomas. This includes alcohol, cigarette smoking, or cell phone use.
Are There Different Types of Gliomas?
While many of benign brain tumors are gliomas, almost 80% of malignant brain tumors are gliomas.
Gliomas are named based on the specific type of glioma, or brain cell, affected. According to the American Cancer Society, there are three types of gliomas, including astrocytomas, oligodendrogliomas, and ependymomas.
- Ependymomas make up less than 2% of all brain tumors and less than 10% of all brain tumors in children. These tumors come from the ependymal cells and because they do not spread into the normal brain tissue, some ependymomas can be cured by surgery. They rarely spread outside the brain. But they do have a high risk of local recurrence and thus are considered malignant.
- Astrocytomas start in brain cells called astrocytes. Most of these brain tumors cannot be cured because they spread all through the normal brain tissue. Astrocytomas are usually classified based on on criteria used by a doctor examining the biopsy under a microscope. Tumors that are grade 1 grow the slowest, while grade 4 tumors, the highest grade, are the fastest growing.
- Oligodendrogliomas are tumors that spread in a similar manner to astrocytomas. Some of these tumors may be slow growing but still spread into nearby tissue. Sometimes they can be cured. A higher grade anaplastic oligodendroglioma grows and spreads more quickly and usually can’t be cured.
What Are the Symptoms of a Glioma?
Symptoms of a glioma are similar to those produced by other malignant brain tumors and depend on the area of the brain affected. The most common symptom is headache -- affecting about half of all people with a brain tumor. Other symptoms can include seizures, memory loss, physical weakness, loss of muscle control, visual symptoms, language problems, cognitive decline, and personality changes. These symptoms may change, according to which part of the brain is affected.
Symptoms may worsen or change as the tumor continues to grow and destroys brain cells, compresses parts of the brain, and causes swelling in the brain and pressure in the skull.
How Are Gliomas Diagnosed?
If a brain tumor is suspected, a brain scan is typically done. This includes a CT scan, an MRI scan (considered to be superior), or both. If the brain scan suggests a brain tumor, a biopsy may be performed for diagnosis. A biopsy may be done as a separate procedure or at the time the tumor is removed if surgery is a treatment option.
How Are Gliomas Graded?
Gliomas are characterized by subtypes and by a numerical grading system. The grade of a tumor means how the cancer cells appear under a microscope. Grade I tumors grow slowly and can sometimes be totally removed by surgery, while grade IV tumors are fast-growing, aggressive, and difficult to treat.
According to the current World Health Organization (WHO) scheme, malignant astrocytomas are classified and graded as follows:
- Grade I gliomas include pilocytic astrocytomas and are more common in children.
- Grade II tumors are diffuse astrocytomas and are low grade.
- Grade III gliomas are diffuse and called anaplastic astrocytoma. They're considered high grade.
- Grade IV glioblastoma are considered high grade.
The oligodendroglial tumors are classified as follows:
- Grade II or low grade oligodendroglioma
- Grade III or anaplastic oligodendroglioma.
The ependymal tumors are classified as subependymoma, ependymoma, and anaplastic ependymoma, with the latter being more aggressive.
The low-grade tumors usually grow slowly but may transform into high-grade tumors.
How Are Gliomas Treated?
Different treatment options are considered for malignant glioma, depending on the location of the tumor, type of glioma (cell type), and grade of malignancy. The patient’s age and physical condition also play a role in determining treatment. Treatment for gliomas is multifaceted and may include:
- Tumor removal by surgery. The patient should be otherwise relatively healthy, and brain function, speech, and mobility is able to be maintained. Imaging techniques such cortical mapping and functional MRI may be used to assist the surgeon in removing the tumor. The goal is to remove as much of the tumor as possible without affecting important brain function. Recurrences of the tumor are frequent.
- Radiation therapy uses high-energy X-rays or other radiation to kill the cancer cells.
- Chemotherapy uses drugs to stop the cancer cell growth. This therapy may be taken by mouth or injected.
- Targeted therapy is a newer type of treatment that may be used to help shrink tumors. It works differently than chemotherapy in that it targets certain proteins that help tumors grow.
- Alternating electric-field therapy uses electrical fields to target cells in the tumor while not hurting normal cells. It's done by putting electrodes directly on the scalp. The device is called Optune. It's given with chemotherapy after surgery and radiation. The FDA has approved it for use in both newly diagnosed adults and adults whose glioblastoma has come back.
- Supportive therapy to improve symptoms and neurologic function include corticosteroids to reduce swelling in the brain caused by the tumor and anticonvulsants to control or prevent seizures.
- Clinical trials, performed to see if new cancer therapies are effective and safe, are another option.
Treatment for Low-Grade Astrocytomas
The primary treatment for low-grade astrocytomas is surgery. However, because these tumors penetrate deep into the brain and grow into normal brain tissue, surgery is sometimes difficult. Radiation is often recommended after surgery or if there is a recurrence. Chemotherapy may also be used after surgery or as part of the treatment of recurrences.
Treatment for High-Grade Astrocytomas
Treatment for high-grade astrocytomas (Grade III anaplastic astrocytomas or Grade IV glioblastomas multiforme) is surgery, if possible. After surgery, radiation therapy, in conjunction with chemotherapy, is the next step. Targeted therapy may be used in some people. Sometimes surgery to remove the high-grade tumor is not possible. Then radiation and chemotherapy are used. If the tumor returns, the surgery may be repeated along with other forms of chemotherapy. Clinical trials may also be recommended to allow patients to use new therapies.
Treatment for Oligodendrogliomas
For oligodendrogliomas, surgery is the first choice of treatment to help relieve symptoms and increase patient survival. Radiation with or without chemotherapy may be given after surgery. Also, chemotherapy or radiation maybe used to shrink a tumor before surgery. If surgery cannot be done, then chemotherapy with or without radiation therapy may be used.
Treatment for Ependymomas and Anaplastic Ependymomas
Ependymomas and anaplastic ependymomas usually do not pass into normal brain tissue as do other gliomas. Therefore, surgery may be highly effective if all of the tumor is removed. However, ependymomas may seed the cerebrospinal fluid so the entire spinal canal needs evaluation with MRI scanning. These tumors are highly responsive to radiation.
What’s the Prognosis for Those With Gliomas?
High-grade gliomas are fast-growing tumors. with a poor prognosis, especially for older patients.