External Radiation Therapy

by National Cancer Institute

(Page 2 of 9)

How Does the Doctor Plan My Treatment?

The high energy rays used for radiation therapy can come from a variety of sources. Your doctor may choose to use x-rays, an electron beam, or cobalt-60 gamma rays. Some cancer treatment centers have special equipment that produces beams of protons or neutrons for radiation therapy. The type of radiation your doctor decides to use depends on what kind of cancer you have and how far into your body the radiation should go. High-energy radiation is used to treat many types of cancer. Low-energy x-rays are used to treat some kinds of skin diseases.

After a physical exam and a review of your medical history, the doctor plans your treatment. In a process called simulation, you will be asked to lie very still on an examining table while the radiation therapist uses a special x-ray machine to define your treatment port or field. This is the exact place on your body where the radiation will be aimed. Depending on the location of your cancer, you may have more than one treatment port.

Simulation may also involve CT scans or other imaging studies to plan how to direct the radiation. Depending on the type of treatment you will be receiving, body molds or other devices that keep you from moving during treatment (immobilization devices) may be made at this time. They will be used each time you have treatment to be sure that you are positioned correctly. Simulation may take from a half hour to about 2 hours.

The radiation therapist often will mark the treatment port on your skin with tattoos or tiny dots of colored, permanent ink. It's important that the radiation be targeted at the same area each time. If the dots appear to be fading, tell your radiation therapist who will darken them so that they can be seen easily.

Once simulation has been done, your doctor will meet with the radiation physicist and the dosimetrist. Based on the results of your medical history, lab tests, x-rays, other treatments you may have had, and the location and kind of cancer you have, they will decide how much radiation is needed, what kind of machine to use to deliver it, and how many treatments you should have.

After you have started the treatments, your doctor and the other members of your health care team will follow your progress by checking your response to treatment and how you are feeling at least once a week. When necessary, your doctor may revise the treatment plan by changing the radiation dose or the number and length of your remaining radiation sessions.

Your nurse will be available daily to discuss your concerns and answer any questions you may have. Be sure to tell your nurse if you are having any side effects or if you notice any unusual symptoms.

How Long Does the Treatment Take?

For most types of cancer, radiation therapy usually is given 5 days a week for 6 or 7 weeks. (When radiation is used for palliative care, the course of treatment is shorter, usually 2 to 3 weeks.) The total dose of radiation and the number of treatments you need will depend on the size, location, and kind of cancer you have, your general health, and other medical treatments you may be receiving.

Using many small doses of daily radiation rather than a few large doses helps protect normal body tissues in the treatment area. Weekend rest breaks allow normal cells to recover.

It's very important that you have all of your scheduled treatments to get the most benefit from your therapy. Missing or delaying treatments can lessen the effectiveness of your radiation treatment.

What Happens During the Treatment Visits?

Before each treatment, you may need to change into a hospital gown or robe. It's best to wear clothing that is easy to take off and put on again.

In the treatment room, the radiation therapist will use the marks on your skin to locate the treatment area and to position you correctly. You may sit in a special chair or lie down on a treatment table. For each external radiation therapy session, you will be in the treatment room about 15 to 30 minutes, but you will be getting radiation for only about 1 to 5 minutes of that time. Receiving external radiation treatments is painless, just like having an x-ray taken. You will not hear, see, or smell the radiation.

The radiation therapist may put special shields (or blocks) between the machine and certain parts of your body to help protect normal tissues and organs. There might also be plastic or plaster forms that help you stay in exactly the right place. You need to remain very still during the treatment so that the radiation reaches only the area where it's needed and the same area is treated each time. You don't have to hold your breath - just breathe normally.

The radiation therapist will leave the treatment room before your treatment begins. The radiation machine is controlled from a nearby area. You will be watched on a television screen or through a window in the control room. Although you may feel alone, keep in mind that the therapist can see and hear you and even talk with you using an intercom in the treatment room. If you should feel ill or very uncomfortable during the treatment, tell your therapist at once. The machine can be stopped at any time.

The machines used for radiation treatments are very large, and they make noises as they move around your body to aim at the treatment area from different angles. Their size and motion may be frightening at first. Remember that the machines are being moved and controlled by your radiation therapist. They are checked constantly to be sure they're working right. If you have concerns about anything that happens in the treatment room, discuss these concerns with the radiation therapist.

What Is Hyperfractionated Radiation Therapy?

Radiation is usually given once daily in a dose that is based on the type and location of the tumor. In hyperfractionated radiation therapy, the daily dose is divided into smaller doses that are given more than once a day. The treatments usually are separated by 4 to 6 hours. Doctors are studying hyperfractionated therapy to learn if it is equal to, or perhaps more effective than, once-a-day therapy and whether there are fewer long-term side effects. Early results of treatment studies of some kinds of tumors are encouraging, and hyperfractionated therapy is becoming a more common way to give radiation treatments for some types of cancer.

What Is Intraoperative Radiation?

Intraoperative radiation combines surgery and radiation therapy. The surgeon first removes as much of the tumor as possible. Before the surgery is completed, a large dose of radiation is given directly to the tumor bed (the area from which the tumor has been removed) and nearby areas where cancer cells might have spread. Sometimes intraoperative radiation is used in addition to external radiation therapy. This gives the cancer cells a larger amount of radiation than would be possible using external radiation alone.

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