Glioma refers to a type of brain tumor that develops from the glial cells, which are specialized cells that surround and support neurons (nerve cells) in the brain. It is generally classified based on which type of glial cell is involved in the tumor:
- Astocytoma - tumors that develop from star-shaped glial cells called astrocytes
- Ependymomas - tumors that arise from ependymal cells that line the ventricles of the brain and the center of the spinal cord
- Oligodendrogliomas - tumors that affect the oligodendrocytes
Gliomas can affect your brain function and be life-threatening depending on their location and rate of growth. Gliomas are one of the most common types of primary brain tumors.
The type of glioma you have helps determine your treatment and your prognosis. In general, glioma treatment options include surgery, radiation therapy, chemotherapy, targeted therapy.
The symptoms of glioma vary by type but may include:
- Nausea or vomiting
- Confusion or a decline in brain function
- Memory loss
- Personality changes or irritability
- Difficulty with balance
- Urinary incontinence
- Vision problems, such as blurred vision, double vision or loss of peripheral vision
- Speech difficulties
- Seizures, especially in someone without a history of seizures
Like most primary brain tumors, the exact cause of gliomas is not known. But there are some factors that may increase your risk of a brain tumor.
Risk factors include:
- Your age. Your risk of a brain tumor increases as you age. Gliomas are most common in adults between 60 and 80 years old. However, a brain tumor can occur at any age. Certain types of gliomas, such as ependymomas and pilocytic astrocytomas, are more common in children and young adults.
- Exposure to radiation. People who have been exposed to a type of radiation called ionizing radiation have an increased risk of brain tumor. Examples of ionizing radiation include radiation therapy used to treat cancer and radiation exposure caused by atomic bombs. More-common forms of radiation, such as electromagnetic fields from power lines and radiofrequency radiation from cellphones and microwave ovens, have not been shown to increase the risk of glioma.
- Family history of glioma. It's rare for glioma to run in families. But having a family history of glioma can double the risk of developing it. Some genes have been weakly associated with glioma, but more study is needed to confirm the link between these genetic variations and brain tumors.
Both genetic and environmental factors play a role in the development of glioma.
Based on knowledge about cancer development in general, lifestyle factors, and the results of genetic research, leading scientists believe that the majority of brain tumors may be linked to interactions between susceptibility genes and environmental toxins. Accordingly, some additional preventive strategies that may be considered, include avoidance of chemical exposure, especially to pesticides, polyvinyl chloride used in plastics manufacturing, and petroleum products.
Diagnosing a glioma usually begins with a medical history review and exam by a brain disorder specialist (neurologist), which includes checking your vision, hearing, balance, coordination and reflexes. Depending on those results, your doctor may request one or more of the tests described below.
Imaging scans help gauge the tumor's effect on your brain activity and function, and blood flow. If a brain scan detects a tumor, especially multiple tumors, your doctor may test for cancer elsewhere in your body. Imaging tests may include:
- Magnetic resonance imaging (MRI) scan. MRI uses a magnetic field and radio waves to create detailed images of the brain. Sometimes a special dye is injected into the bloodstream to make tumors appear different from healthy tissue (MR angiography). Perfusion, functional and intraoperative MRI scans may be done to identify blood flow and volume, critical brain areas involved in speech and motor activity, and the tumor's precise location.
- Computerized tomography (CT) scan. A CT scan uses a sophisticated X-ray machine linked to a computer to produce detailed, two-dimensional images of the brain. A CT scan can help identify certain types of tumors, especially those close to or involving bone.
- Other brain scans. Other tests — such as magnetic resonance spectroscopy (MRS), single-photon emission computerized tomography (SPECT) or positron emission tomography (PET) scanning — help doctors gauge brain tumor activity and blood flow.
- Angiogram. A special dye is injected into the arteries that feed the brain, making the blood vessels visible on X-ray. This test helps locate blood vessels in and around a brain tumor.
Your surgeon will typically do a biopsy to diagnose a brain tumor and confirm its type. A biopsy involves removing a tiny piece of tumor tissue for examination under a microscope as part of the surgery to remove the tumor.
The sample is examined instantly by a specialist in assessing brain tissue tumors (neuropathologist) to identify the kind of tumor, which is critical in determining the appropriate treatment for you. Mayo Clinic's neuropathologists are internationally known for their expertise. Studies show that the diagnosis may change substantially for at least one-fourth of people when an experienced neuropathologist does the analysis.
Gliomas are rarely curable. The prognosis for patients with high-grade gliomas is generally poor, and is especially so for older patients. Of 10,000 Americans diagnosed each year with malignant gliomas, about half are alive one year after diagnosis, and 25% after two years. Those with anaplastic astrocytoma survive about three years. Glioblastoma multiforme has a worse prognosis with less than a 12-month average survival after diagnosis, though this has extended to 14 months with more recent treatments.
For low-grade tumors, the prognosis is somewhat more optimistic. Patients diagnosed with a low-grade glioma are 17 times as likely to die as matched patients in the general population. The age-standardized 10-year relative survival rate was 47%. One study reported that low-grade oligodendroglioma patients have a median survival of 11.6 years; another reported a median survival of 16.7 years.
This group comprises anaplastic astrocytomas and glioblastoma multiforme.
Diffuse intrinsic pontic glioma:
Diffuse intrinsic pontine glioma primarily affects children, usually between the ages of 5 and 7. The median survival time with DIPG is under 12 months. Surgery to attempt tumour removal is usually not possible or advisable for DIPG. By their very nature, these tumours invade diffusely throughout the brain stem, growing between normal nerve cells. Aggressive surgery would cause severe damage to neural structures vital for arm and leg movement, eye movement, swallowing, breathing, and even consciousness. Trials of drug candidates have been unsuccessful.
Surgery to remove as much of the tumor as possible is usually the first step in treating most types of gliomas. In some cases, gliomas are small and easy to separate from surrounding healthy brain tissue, which makes complete surgical removal possible. In other cases, tumors can't be separated from surrounding tissue, or they're located near sensitive areas in your brain and make surgery risky. In these situations your doctor removes as much of the tumor as is safe. Even removing a portion of the tumor may help reduce your signs and symptoms.
In some cases, neuropathologists may analyze tissue samples removed by a surgeon and report the results while surgery is underway. This information helps the surgeon decide how much tissue to remove.
Radiation therapy usually follows surgery in treatment of glioma, especially high-grade gliomas. Radiation uses high-energy beams, such as X-rays or protons, to kill tumor cells.
Chemotherapy uses drugs to kill tumor cells. Chemotherapy drugs can be taken in pill form (orally) or injected into a vein (intravenously). Chemotherapy is usually used in combination with radiation therapy to treat gliomas. The chemotherapy drug used most often to treat gliomas is temozolomide (Temodar), which is taken as a pill.
- Polifeprosan 20 with carmustine (Gliadel) - FDA-approved indication: Expanding the indication to include patients with malignant glioma undergoing primary surgical resection.
- Temozolomide (Temodar) - FDA-approved indication: Treatment of adult patients with newly diagnosed glioblastoma multiforme concomitatly with radiotherapy and then as maintenance treatment
- Bevacizumab (Avastin) - FDA approved indication: Treatment of glioblastoma with progressive disease following prior therapy
Refer to Research Publications.