Radiation Therapy for Brain Tumors
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This page discusses the use of radiation for the treatment of brain tumors. For a thorough review of radiation for cancer treatment, please see the ]]>radiation treatment monograph]]> .
Radiation therapy is the use of penetrating beams of high-energy waves or streams of particles called x-rays to treat disease. Radiation therapy destroys the ability of cancer cells to grow and divide.
The majority of potentially lethal brain tumors are astrocytomas, derived from the brain’s glial cells. These are ]]>classified into four categories]]> according to their prognosis. Although there are other brain tumors for which radiation is a recommended treatment option, a general discussion focused on gliomas can be applied to other malignant brain tumors. Specific treatment choices are beyond the scope of this article and vary from hospital to hospital and from moment to moment.
Radiation is often used alone to treat brain tumors. The consensus, so far as one exists, is to try to combine ]]>surgery]]> , radiation, and ]]>chemotherapy]]> in the treatment of any potentially lethal brain tumor. Beyond that, the multiple options available for all three modes of treatment and the rapid advances in technology create an ever-changing array of recommendations. All attempts to improve outcomes—better drugs, genetics, higher doses of radiation—have been unsuccessful so far.
External Radiation Therapy
External radiation therapy is often used to treat brain cancer. In external radiation therapy, rays are directed at the tumor from outside the body.
There are many new ways that the radiation oncologist may customize your treatment to kill as much cancer while sparing as much normal tissue as possible. The radiation oncologist will determine how many treatments you will receive; they will usually be given once a day, or possibly twice a day if you are participating in a clinical trial. Each treatment generally only takes a few minutes, and the total treatment time can range from 5 to 8 weeks depending on the total dose required.
Radiation therapy can be given to treat cancer at its initial site or once it has spread. In some cases, once cancer has spread, radiation is much less effective. However, the treatments may improve symptoms caused by the cancer, such as pain and fatigue.
Another form of radiation therapy used to treat brain cancer is stereotactic radiosurgery. Perhaps the most sophisticated of all medical procedures, stereotactic radiosurgery (or the gamma knife) creates a computerized image of a brain tumor using CT or MRI scanning. The computer, guided by this image, then focuses an array of gamma ray emitters surrounding your head so that only the tumor is irradiated. Damage to surrounding normal tissue is minimal. This technique is most useful for tumors less than 3 centimeters (cm) in diameter.
When a gamma knife is not available, an equally effective device is stereotactic radiotherapy that is mounted to the linear accelerator. Both types (gamma knife and linear accelerator-based surgery) allow for close definition of the tumor and exacting dose delivery.
Internal Radiation Therapy
Internal radiation therapy, also called brachytherapy, places the radiation source as close as possible to the cancer cells. Radioactive material, sealed in a thin wire, catheter, or tube, is placed directly into the affected tissue. This form of radiation is often used only when a tumor recurs, because this type of radiation can damage nearby normal brain tissue.
Course of Treatment
Radiation treatments usually follow surgery and may be either external or stereotactic, depending on the unique characteristics of each tumor. Internal radiation is usually only used if a tumor recurs. Low-grade tumors may not require radiation if surgical resection is judged to be complete. However, tumor recurrence may respond to radiation.
A typical course of treatment for a moderate to high-grade astrocytoma will begin with surgery, both to obtain a tissue specimen for laboratory analysis and to remove as much tumor as possible without damaging normal brain tissue. During surgery, a radioactive implant may be placed in your body to deliver brachytherapy, but only if the center at which you are being treated is experienced with this technique, the tumor location is peripheral, and the tumor bed is very small. Tumors in highly sensitive or remote areas of the brain may not be accessible to surgical intervention.
Chemotherapy, if indicated, is often given during and then after radiation for all but low-grade tumors.
Combining surgery with subsequent radiation and chemotherapy for high-risk tumors yields average overall survival rates up to 8 years for low-grade (Type I and II) astrocytomas and oligodendrogliomas; 2 to 3 years for Grade III anaplastic astrocytomas; and 1 year for Grade IV glioblastoma multiforme. These survival rates are influenced considerably by the patient’s age and functional status.
Brain cancer is not often cured, but quality of life is improved and survival is prolonged with the combined approaches currently used. For example, survival of patients under 65 years of age with glioblastoma is prolonged from 7 to 9 months to 11 to 13 months when radiation therapy is added to the treatment program.
Beyond the generalized complications of cancer treatment, radiation can damage normal brain tissue, causing a failure or decrease of whatever brain function is affected. Generalized brain swelling is a potentially lethal complication of both brain surgery and radiation. It requires careful observation during post-operative or post-radiation recovery and can frequently be ]]>treated or prevented]]> using cortisone-like drugs.
When to Contact Your Health Care Provider
Call your health care provider if you:
- Develop side effects from the treatment
- Develop new or unusual symptoms
- Your skin is red, blistered, or swollen
For more information on radiation therapy, including how to manage the side effects, please see the ]]>radiation therapy treatment monograph.]]>
Sagar SM, Israel MA. Primary and metastatic tumors of the nervous system. In:
Available at: www.harrisonsonline.com .
Accessed November 2002.
National Cancer Institute
American Cancer Society
Last reviewed February 2003 by ]]>Jondavid Pollock, MD, PhD]]>
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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