Radiation:

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

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:

• Three-dimensional conformal radiation therapy (3D-CRT) uses computer-generated imaging scans to map the tumorâ ' s location. Radiation beams are then used that conform to the three-dimensional shape of the tumor.
• Intensity-modulated radiation therapy (IMRT) is a more advanced and higher-dose form of 3D-CRT.
• Conformalproton beam radiation therapy is also similar to 3D-CRT but uses proton beams instead of x-ray energy. It is not yet widely available.

Stereotactic Radiosurgery

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:

• Stereotaxy allows precisely focused, high-dose beams to be delivered to gliomas fewer than 1.25 inches in diameter with less damage to surrounding tissues.
• Stereotactic radiosurgery can help reach small tumors located deep in the brain that were previously considered inoperable.
• Sometimes with stereotaxy only a single treatment may be needed.
• Unlike traditional radiotherapy, stereotactic radiotherapy can be repeated, so it is useful for recurrent tumors when a patient has already received standard radiation treatments.
• Combining stereotaxy with techniques that gauge speech and other mental functions in patients who are awake during the procedure can allow removal of brain tissue with a lower risk for complications in areas that affect such functioning.

The Planning Procedure. Stereotactic radiosurgery usually begins with a series of steps designed to plan the radiation target:

• First, the patient is given a local anesthetic. In the standard operation, the patient's head must be totally immobilized by screwing a device known as a stereotactic frame into the patient's skull. (The frame procedure is effective only on brain tumors that have regular margins.) The frame is removed as soon as the whole procedure has been completed (about 3 - 4 hours).
• A three-dimensional map, usually using magnetic resonance imaging (MRI) scans, is made of the patient's brain.
• A computer program calculates dosage levels and specific areas for radiation targeting.

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.

• The gamma knife uses gamma rays that are sent from multiple points to converge at a single point on the tumor. Although each gamma-ray beam is very low dosage, when the beams converge, the intensity and destructive power is very high. The gamma knife is limited to very small tumors and so is generally useful as a booster after standard radiation, surgery, chemotherapy, or combinations.
• The linear accelerator (LINAC) produces protons (positively-charged atomic particles) in patterns that are matched to the tumor shape. The patient is positioned on a bed that can be moved to allow flexible positioning. It allows treatment over multiple sessions of small doses (fractionated stereotactic radiotherapy), instead of a single session. This means that larger tumors can be treated.

Drugs Used With Radiation

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.

Side Effects of 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.