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External Beam Radiation

What is external beam radiation therapy?

External beam radiation therapy comes from a machine that aims radiation at your cancer. The machine is large and may be noisy. It does not touch you, but rotates around you, sending radiation to your body from many directions.External beam radiation therapy is a local treatment, meaning that the radiation is aimed only at a specific part of your body. For example, if you have lung cancer, you will get radiation to your chest only and not the rest of your body.

External beam radiation therapy comes from a machine that aims radiation at your cancer.

How often will I get external beam radiation therapy?

Most people get external beam radiation therapy once a day, 5 days a week, Monday through Friday. Treatment lasts for 2 to 10 weeks, depending on the type of cancer you have and the goal of your treatment. The time between your first and last radiation therapy sessions is called a course of treatment.Radiation is sometimes given in smaller doses twice a day (hyperfractionated radiation therapy). Your doctor may prescribe this type of treatment if he or she feels that it will work better. Although side effects may be more severe, there may be fewer late side effects. Doctors are doing research to see which types of cancer are best treated this way.

Where do I go for external beam radiation therapy?

Most of the time, you will get external beam radiation therapy as an outpatient. This means that you will have treatment at a clinic or radiation therapy center and will not have to stay in the hospital.

What happens before my first external beam radiation treatment?

You will have a 1- to 2-hour meeting with your doctor or nurse before you begin radiation therapy. At this time, you will have a physical exam, talk about your medical history, and maybe have imaging tests. Your doctor or nurse will discuss external beam radiation therapy, its benefits and side effects, and ways you can care for yourself during and after treatment. You can then choose whether to have external beam radiation therapy.If you agree to have external beam radiation therapy, you will be scheduled for a treatment planning session called a simulation. At this time:

  • A radiation oncologist and radiation therapist will define your treatment area (also called a treatment port or treatment field). This refers to the places in your body that will get radiation. You will be asked to lie very still while x-rays or scans are taken to define the treatment area.
  • The radiation therapist will then put small marks (tattoos or dots of colored ink) on your skin to mark the treatment area. You will need these marks throughout the course of radiation therapy. The radiation therapist will use them each day to make sure you are in the correct position. Tattoos are about the size of a freckle and will remain on your skin for the rest of your life. Ink markings will fade over time. Be careful not to remove them and make sure to tell the radiation therapist if they fade or lose color.
  • You may need a body mold. This is a plastic or plaster form that helps keep you from moving during treatment. It also helps make sure that you are in the exact same position each day of treatment.
  • If you are getting radiation to the head, you may need a mask. The mask has air holes, and holes can be cut for your eyes, nose, and mouth. It attaches to the table where you will lie to receive your treatments. The mask helps keep your head from moving so that you are in the exact same position for each treatment.

If the body mold or mask makes you feel anxious, see Your Feelings During Radiation Therapy for ways to relax during treatment.

What should I wear when I get external beam radiation therapy?

Wear clothes that are comfortable and made of soft fabric, such as cotton. Choose clothes that are easy to take off, since you may need to change into a hospital gown or show the area that is being treated. Do not wear clothes that are tight, such as close-fitting collars or waistbands, near your treatment area. Also, do not wear jewelry, BAND-AIDS®, powder, lotion, or deodorant in or near your treatment area, and do not use deodorant soap before your treatment.

What happens during treatment sessions?

  • You may be asked to change into a hospital gown or robe.
  • You will go to a treatment room where you will receive radiation.
  • Depending on where your cancer is, you will either sit in a chair or lie down on a treatment table. The radiation therapist will use your body mold and skin marks to help you get into position.
  • You may see colored lights pointed at your skin marks. These lights are harmless and help the therapist position you for treatment each day.
  • You will need to stay very still so the radiation goes to the exact same place each time. You can breathe as you always do and do not have to hold your breath.

The radiation therapist will leave the room just before your treatment begins. He or she will go to a nearby room to control the radiation machine and watch you on a TV screen or through a window. You are not alone, even though it may feel that way. The radiation therapist can see you on the screen or through the window. He or she can hear and talk with you through a speaker in your treatment room. Make sure to tell the therapist if you feel sick or are uncomfortable. He or she can stop the radiation machine at any time. You cannot feel, hear, see, or smell radiation.Your entire visit may last from 30 minutes to 1 hour. Most of that time is spent setting you in the correct position. You will get radiation for only 1 to 5 minutes. If you are getting IMRT, your treatment may last longer. Your visit may also take longer if your treatment team needs to take and review x-rays.

Your radiation therapist can see, hear, and talk with you at all times while you are getting external beam radiation therapy.

Will external beam radiation therapy make me radioactive?

No, external beam radiation therapy does not make people radioactive. You may safely be around other people, even babies and young children.

How can I relax during my treatment sessions?

  • Bring something to read or do while in the waiting room.
  • Ask if you can listen to music or books on tape.
  • Meditate, breathe deeply, use imagery, or find other ways to relax.
This information is not intended to replace the advice of a doctor. Navigating Care disclaims any liability for the decisions you make based on this information. This information was sourced and adapted from the National Cancer Institute's web site,

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