Q. What is a brain tumor?
A. "Tumor" is a general term describing new growth of cells in an inappropriate manner (i.e. serving no useful purpose). The National Cancer Institute defines a tumor as an abnormal mass of tissue that results from excessive cell division. They may be benign (not cancerous) or malignant (cancerous). Brain tumors are tumors of the central nervous system (CNS), which includes the brain, spinal cord and associated tissue.
Q. What are the most common types of brain tumors?
A. There are two types of brain tumors, primary and secondary. Primary brain tumors grow from cells that are part of the central nervous system. Primary brain tumors may be either benign (non-cancerous) or malignant (cancerous). Secondary brain tumors are cancerous tumors that arise from cancer cells that travel from other parts of the body and invade the brain.
Most primary tumors of the central nervous system are named according to the specific type of cells in the nervous system from which they arise. The most common primary brain tumors in adults are malignant gliomas, which arise from cells that support neurons, and meningiomas, generally nonmalignant tumors that arise from the membrane that lines the skull and covers the nervous system.
Q. What causes primary brain tumors?
A. Scientists do not know what causes brain tumors. There are some risk factors that scientists believe may contribute to the development of brain tumors. For primary brain tumors, two environmental risk factors are exposure of the head to Xrays and a history of disorders of the immune system. Certain genetic disorders present risk factors for specific types of brain tumors, both cancerous and noncancerous.
Q. What are the dangers of a benign tumor?
A. The word “benign” is misleading because it implies that the tumor presents no danger to the patient. In fact benign tumors of the central nervous system can cause very serious disability and even death for two main reasons. First, the brain is enclosed in the skull, which cannot expand to make room for a growing tumor, so the tumor may compress and damage delicate brain structures. For example, benign tumors grow on or near the optic nerve, affecting vision. Some benign brain tumors can change over time, becoming malignant. Because of the potentially serious problems associated with noncancerous brain tumors they are often described as being "high-grade" (rapidly growing) or "low-grade" (slowly growing), rather than malignant or benign.
Q. How are brain tumors treated?
A. Doctors have three basic treatment options for brain tumors: surgery, radiation therapy, and chemotherapy. Surgery is usually the first and the most common treatment, and is associated with the greatest amount of therapeutic effect. To remove the tumor from the brain, a neurosurgeon will remove a piece of bone to gain access to the brain. This operation is called a craniotomy. Usually the bone will be put back in place and secured with small plates and screws. However, sometimes the bone cannot be replaced, or cannot be replaced immediately, in which case other materials will be used to cover the hole in the skull and protect the brain.
Radiation therapy is often prescribed following surgery, or in the case of inoperable tumors, instead of surgery. When used following surgery, radiation therapy is generally acknowledged to give an improved therapeutic effect over surgery alone. Radiation therapy uses Xrays produced by a variety of methods including linear accelerators, gamma knife, or proton beam to kill tumor cells or shrink tumors without opening the skull (external-beam radiation therapy). Radiation therapy may also be used by putting materials that produce radiation (radioisotopes) through thin plastic tubes into the tumor to kill cancer cells from the inside, known as brachytherapy.
Chemotherapy uses drugs to kill tumor cells. Chemotherapy may be taken by pill, or it may be put into the body by a needle in the vein or muscle. Chemotherapy is called a systemic treatment because the drug enters the bloodstream, travels through the body, and can kill cancer cells throughout the body.
Biological therapies are therapies that enhance or improve the body’s natural ability to fight disease, or are based on the normal mechanisms utilized to control growth. One example of a type of biological therapy is “immunotherapy,” which uses the body's immune system to control or destroy tumor cells. Biological therapies are sometimes referred to as “biological response modifiers” because they are intended to optimize or somehow change the body’s response to growing tumor cells.
