What are gliomas?

Risk factors: Most brain tumors have no known risk factors. Exposure to radiation or radiation of the brain may cause a brain tumor. There are no studies that prove brain tumors are caused by cell phone use, electric lines, injury or accidents, exposure to toxic fumes, hair dyes, or any food or food product. The National Cancer Institute reports that exposure to vinyl chloride, a gas used in making plastic, may increase the chance of developing glioma.

Etiology and the disease process: There is no known cause for glioma. Malignant gliomas are aggressive tumors that may spread quickly throughout the brain. Because the brain controls almost all body functions, a rapidly growing tumor may cause problems with breathing, sight, hearing, smell, balance, body temperature, and other functions, creating life-threatening conditions. As the glioma increases in size, the symptoms progress, leading to difficulty with activities of daily living. Gliomas are considered incurable, and once diagnosed, a survival time of less than one year is not unusual.

Incidence: Gliomas account for approximately 42 percent of all central nervous system (CNS) tumors and 77 percent of all malignant CNS tumors. Just over 9,000 gliomas are diagnosed each year in the United States. The average age at diagnosis for adults is fifty-four. Children with brain tumors are diagnosed evenly over the ages from birth to nineteen years.

Symptoms: Depending on the type and grade of the tumor, tumors may grow one to two years before symptoms develop. The brain can adjust to a slow-growing, low-grade tumor and may adapt over time, but symptoms eventually will occur. A high-grade or aggressive tumor may cause dramatic symptoms that develop quickly. The most common symptoms are headache, seizures or convulsions, weakness or paralysis, nausea or vomiting, difficulty walking due to poor balance, behavior changes, confusion, and vision changes.

Screening and diagnosis: There are no screening tests for gliomas. Diagnosis begins when the patient complains of symptoms suggestive of a glioma. A physician with a specialty in neurology or neurosurgery should be involved in a comprehensive physical examination of the patient. Diagnostic radiology procedures such as computed tomography (CT) and magnetic resonance imaging (MRI) of the head are most commonly used when a patient exhibits symptoms. A positron emission tomography (PET) scan may be used as it can assist in determining if the tumor is malignant. A biopsy is generally not done for diagnosis because of inability to reach the tumor, but one is usually done at the time of surgery to determine the specific cell type. Staging is based on identifying the location of the primary tumor (T X-4), evidence of metastasis (M X-1), and grade (G I-IV).

Treatment and therapy: Treatment for gliomas is difficult and usually combines surgery (if the tumor can be reached) and radiation. Radiosurgery is an option if the tumor is inoperable. Chemotherapy has limited use because of the difficulty of getting the drugs into the brain in the proper amounts to kill cells. Carmustine (BCNU) is one drug that is able to penetrate into the brain and has shown some activity against gliomas. It does have toxicity that limits its use. Recommendations for treatment are consistently moving toward surgery, radiation, and systemic chemotherapy. Advances in the treatment of gliomas include a wafer with carmustine that is placed into the surgical site after removal of the tumor. Temozolomide (Temodar), an oral drug with few side effects, has shown activity when a glioma returns. Clinical studies are ongoing to determine other chemotherapy combinations that may be useful in treating gliomas.

Prognosis, prevention, and outcomes: The prognosis depends on the type of the glioma, the age of the patient, and the symptoms of the patient when diagnosed. Gliomas are difficult to treat, and survival time is often limited. Slower growing, low-grade tumors, even when treated successfully at first, have the potential to grow back and progress. Avoiding radiation to the head is the only documented prevention. If the tumor is treated successfully, which is rare, there may still be major physical limitations that exist from side effects of the tumor or its treatment.

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