The National Cancer Institute describes brain tumors as the abnormal growth of cells; brain tumors can form in any part of the brain or the spinal cord, and together they are known as brain and central nervous system tumors. Brain tumors are classified in various ways, depending on the types of cells that make up the tumor and the location of the cancer, but radiation is a commonly used treatment for these cancers.
Significance
According to the American Brain Tumor Association, in 2010, approximately 62,930 new diagnoses of primary brain tumors will be made in the United States. Brain tumors are the second most common cause of cancer deaths in children up to 20 years of age, as well as males 39 years old or younger.
Function
Radiation therapy is a commonly used mode of treatment for brain tumors. This kind of therapy uses high-energy rays like X-rays to kill cancer cells, according to the National Cancer Institute. It can be used alone or in conjunction with other treatments. Radiation is typically used in place of surgery if the tumor is inoperable or the patient is not well enough for surgery; it can be administered after surgery to eradicate any leftover cancer cells; or it can be used before surgery to help shrink the tumor so it can be removed more easily. Radiation can also be used palliatively to ease any symptoms the brain tumor may be causing.
External Radiation
Radiation therapy for brain tumors may be given externally or internally. External beam radiation therapy (EBRT) is the most common way of giving radiation therapy, according to the American Cancer Society, and it can be administered in various ways. EBRT consists of aiming radiation at the cancerous area from a machine outside the body. Treatments are typically given five days a week for several weeks, with each session lasting 15 to 30 minutes. Forms of EBRT can include stereotactic radiosurgery, intensity modulated radiation therapy, conformal proton beam radiation therapy and three-dimensional conformal radiation therapy.
Internal Radiation
Another way of giving radiation therapy is internal radiation, or brachytherapy. This may also be called interstitial radiotherapy, according to the American Cancer Society. This kind of radiation involves placing radioactive substances right into or near the tumor area. The radiation is not extremely strong, so it only affects the tumor and not healthy tissue around it. The American Cancer Society says this mode of radiation therapy is typically given along with EBRT so that the tumor area gets a higher dose of radiation, while surrounding areas that may have cancer cells that have spread get a lower dose.
Effects
Side effects of radiation occur because while the radiation kills cancer cells, it also affects normal, healthy brain tissue. The effects of radiation can include irritability, fatigue, nausea or vomiting, headaches, memory loss, and trouble concentrating. Effects can vary, depending on how much of the brain is irradiated and what part of the brain is exposed to radiation. Very rarely, dead tissue forms near the tumor site as a result of radiation; the American Cancer Society calls this radiation necrosis. This is a rare side effect, but if it occurs, surgery to remove it may be necessary.
