A brain tumor is an abnormal growth consisting of cells reproducing uncontrollably. A benign brain tumor is composed of harmless cells, and is contained within distinct boundaries. Most benign tumors can be removed surgically. Malignant tumors are comprised of cancerous cells; they lack distinct borders and often branch out into other areas of the brain, making total removal challenging. In addition to surgery, malignant tumors often require radiation therapy to treat residual cancer in adjacent tissue.
Rationale for Aggressive Radiation Therapy
Radiation therapy uses high-energy beams of X-rays, gamma rays, electrons or protons to damage vital molecules in tumor cells, thereby killing them. It is employed when it is not possible to completely remove the primary tumor surgically. After most of a primary malignant tumor is removed, radiation therapy is administered because residual cancer cells often remain in brain tissue, potentially allowing the tumor to redevelop. Radiation can also be used instead of surgery to treat inoperable tumors. According to the International Radiosurgery Association, the survival rate for patients with malignant tumors more than doubles when they are treated with radiation therapy.
External-Beam Radiation Therapy
According to the National Cancer Institute, radiation oncologists use several methods to treat primary brain tumors, but the most commonly employed is external-beam radiation. External-beam radiation can be concentrated on the area of the brain where the tumor is, or it can be delivered to the whole brain. Several types of external-beam radiation are produced using a beam of high-energy particles generated by a machine called a linear accelerator to target the tumor. The beam penetrates the skull and travels through healthy brain tissue to reach and destroy the tumor.
Stereotactic Radiosurgery
According to the Oncology Channel, stereotactic radiosurgery delivers a very concentrated, high-energy dose of radiation to a tumor. This method uses extremely accurate, image-guided tumor targeting. Using CT or MRI imaging, the radiologist determines the precise location of the tumor, and high-energy radiation beams are focused on the tumor from different angles. Stereotactic radiosurgery can deliver higher doses of more precise radiation to the tumor than external beam radiation, and avoids damaging surrounding healthy tissue.
Brachytherapy
Brachytherapy is a procedure in which tiny capsules containing radioactive isotopes are placed within the tumor to deliver concentrated radiation. As the isotopes decay naturally, they emit radiation that destroys the tumor cells. In permanent brachytherapy, known as interstitial brachytherapy, the tiny capsules are inserted into the tumor and remain there indefinitely. They do not cause discomfort or harm the patient. Brachytherapy is often used to treat recurrent disease at a site previously treated by external-beam radiation. It spares healthy tissues near the tumor, and requires a shorter length of treatment.
Side Effects of Radiation Treatment
According to EMedicine Health, side effects of radiation therapy vary, depending on the part of the brain being treated, the type of radiation received and the total dose of radiation. Fatigue is the most typical side effect, and may last for many months after treatment. Other common side effects include hair loss, nausea, vomiting, loss of appetite, skin irritation, potential hearing loss and neurologic effects. The most apparent long-term side effect is a gradual decline in some higher brain functions, which develops over a few years. This shows up in many patients as a memory problem.
