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Radiation therapy, also called radiotherapy, plays a central role in the treatment of most brain tumors.
Various radiation treatments are used. Radiation is usually given externally, from a source outside the body that directs radiation beams. In some cases, internal radiation may be used as a booster to external-beam radiation. Internal radiation (also called interstitial radiation) generally involves brachytherapy, which uses radioactive "seeds" implanted directly in the tumor site.
Radiotherapy after Surgery. Even when it appears that the entire tumor has been surgically removed, microscopic cancer cells often remain in the surrounding brain tissue. Radiation targets the residual tumor with the goal of reducing its size or stopping its progression. If the entire tumor cannot be removed safely, postoperative radiotherapy is often recommended. Even some benign gliomas may require radiation, since they may be life-threatening if their growth is not controlled.
Radiotherapy When Surgery Is not Appropriate. Radiotherapy may be used instead of surgery for inaccessible tumors or for tumors that have properties that are particularly responsive to radiotherapy.
Radiotherapy and Chemotherapy (Radiochemotherapy). Combining chemotherapy with radiotherapy is beneficial in some patients with high-grade tumors.
Conventional radiotherapy uses external beams aimed directly at the tumor and is usually recommended for large or infiltrating tumors. It begins about a week after surgery and continues on an outpatient basis 5 days per week for 6 weeks. Older adults tend to have a more limited response to external-beam radiation therapy than younger people. Conventional external-beam radiation techniques include:
Stereotactic radiosurgery, also called stereotactic radiotherapy or stereotaxy, is an alternative to conventional radiotherapy that has been developed to allow highly targeted radiation to be delivered directly to the small tumors while avoiding healthy brain tissue. The term radiosurgery is used because the destruction is so precise that it acts almost like a surgical knife. Benefits of stereotactic radiosurgery include:
The Planning Procedure. Stereotactic radiosurgery usually begins with a series of steps designed to plan the radiation target:
Advanced imaging techniques are now allowing frameless stereotaxy, which eliminates the frame and may be effective on more tumors.
Delivery of Radiation Beams. Once the preliminary planning stage has been completed, treatment begins. Several advanced machines, such as the gamma knife and adapted linear accelerator (LINAC), are being used with stereotaxy and can deliver very focused beams of radiation. Actual treatment takes 10 minutes to 1 hour.
Researchers are studying drugs that may be used along with radiation to increase the effectiveness of the treatment.
Radioprotectors. Drugs such as amifosistine (Ethyol) may protect healthy cells during radiation.
Radiosensitizers. Drugs such as fluorouracil (5-FU) and cisplatin (Platinol) may help make cancerous cells more sensitive to radiation.
Common Side Effects. Side effects of radiotherapy may vary depending on the tumor type and radiation treatment. Side effects may include hair loss, fatigue, and nausea and vomiting. Skin irritation and sensitivity may develop in the areas being treated. To prevent further irritation, avoid scratching or rubbing, avoid direct sunlight and heating pads, and do not attempt to treat the symptoms yourself. (Ask your doctor or radiation therapist for advice.) Brain swelling (edema) is another common radiotherapy side effect, which can sometimes cause an increase in brain tumor symptoms. Edema can be treated with steroids.
Tissue Injury. Radiation necrosis (total destruction of nearby healthy tissue) occurs in about 25% of patients treated with intensive radiation. Radiation necrosis can cause brain swelling and reduction in mental functions. The condition is treated with steroids. If steroids prove ineffective, surgery may be required to remove the damaged tissue.
New Tumors. Radiation therapy for childhood cancer is the most important risk factor for developing new brain and spinal column tumors. The risk appears greatest for children who received radiation therapy before age 5. Researchers found that the risk of second primary tumors increased in relation to the radiation dose used to treat the first cancer.
Stroke. Survivors of childhood brain tumors who were treated with high doses of cranial radiation (especially doses greater than 50Gy) may be at increased risk of having a stroke later in life. In a study of nearly 2,000 brain tumor survivors, the average length of time from cancer diagnosis to stroke was 14 years.
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