What is external beam radiation therapy for cancer?

Radiation treatment uses high-energy rays or radioactive material to kill cancer cells or to keep them from growing. In external beam treatment, a beam of radiation from a machine is aimed at an area of the body. This treatment is usually given 5 days a week, over the course of a few weeks. There may be other treatment schedules. For example, some schedules have treatments 2 times a day. How long your treatment lasts depends on the type of cancer you have.

One common form of external beam treatment is conformal therapy. This uses a precise amount of radiation that is carefully targeted at a tumour. This limits radiation exposure to healthy tissue. The treatment itself is painless.

External beam radiation treatment can cause some side effects. It can make the skin near the treated area sore. The skin may turn red or dark, like a burn. The treatment can cause fatigue, nausea, vomiting, and diarrhea. Areas inside your body can get sore. For instance, your throat may hurt if the radiation is aimed there. And you may feel very tired for 4 to 6 weeks after your last treatment. Talk to your doctor about ways to treat the side effects.

Most side effects usually go away within a few weeks after treatment ends. Some side effects last longer or may not show up until much later. And in some cases, a side effect may be permanent.

How is it done?

• You may need to put on a hospital gown or robe. Wear clothing that is comfortable and easy to take off and put on again later.
• The radiation therapist will mark the treatment spot with tattoos or tiny dots of ink. The radiation must focus on the same area every time. If the dots seem to fade between treatments, tell your radiation therapist.
• You may have shields, or blocks, between the machine and other parts of your body. The shields protect those parts of your body from radiation.
• You'll be asked not to move during treatment. If you're having radiation treatment to the head, you may wear a special mask over your face to keep your head still. Other types of braces or casts may be used to help you be in the exact same position for each treatment. If you keep still, then the radiation goes only where it is needed. You can breathe normally.
• Expect the radiation machine to make noises, such as humming and clicking. The sound may worry you, but the machine is under the therapist's control. The machine is checked often to make sure it works as it should. If you are nervous, tell the radiation therapist. Ask any questions you have.
• Talk to your doctor about what activities you can do before, during, and after treatments.

How long does it take?

External beam treatment takes only a few minutes. But allow 30 minutes to an hour for each visit.