What to Expect Before and During Radiation Therapy


Most people have external beam radiation therapy with the same dose of radiation once a day, 5 days a week, Monday through Friday. Treatment lasts up to 6 weeks, depending on the type of cancer you have and the treatment goal. This span of time is called a course of treatment.

Sometimes, the radiation dose or schedule is changed to reach the total dose of radiation more quickly. This can be done in one of these ways:

  • Accelerated fractionation, which gives the half of the usual daily dose of radiation twice each day.
  • Hyperfractionation, which is a smaller than usual daily dose of radiation given twice each day.
  • Hypofractionation, which is a larger than usual daily dose of radiation given once a day for up to 3 weeks.

The doctor may prescribe one of these treatment schedules if he or she feels that it will work better for the type of cancer you have.


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 decide to have external beam radiation therapy, you will be scheduled for a treatment planning session called a simulation. At this time:

  • A radiation oncologist (a doctor who specializes in using radiation to treat cancer) and radiation therapist will figure out your treatment area. You may also hear the treatment area referred to as the treatment port or treatment field. These terms refer 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.
  • The radiation therapist will tattoo or draw small dots of colored ink on your skin to mark the treatment area. These dots will be needed throughout your course of radiation therapy. The radiation therapist will use them to make sure you are in exactly the same position for every treatment. The dots are about the size of a freckle. If the dots are tattooed, they will remain on your skin for the rest of your life. Ink markings will fade over time. Be careful not to remove them and tell the radiation therapist if they have faded or lost color.
  • A body mold may be made of the part of the body that is being treated. This is a plastic or plaster form that keeps you from moving during treatment. It also helps make sure that you are in exactly the same position for each treatment.
  • If you are getting radiation to the head and neck area you may be fitted for a mask. The mask has many air holes. It attaches to the table where you will lie for your treatments. The mask helps keep your head from moving so that you are in exactly the same position for each treatment.

Wear clothes that are comfortable and made of soft fabric, such as fleece or cotton. Choose clothes that are easy to take off, since you may need to expose the treatment area or change into a hospital gown. Do not wear clothes that are tight, such as close-fitting collars or waistbands, near your treatment area. Also, do not wear jewelry, adhesive bandages, or powder in the treatment area.


  • You may be asked to change into a hospital gown or robe depending on area being treated.
  • You will go to the treatment room where you will receive radiation. The temperature in this room will be very cool.
    Depending on where your cancer is, you will either lie face or head down on a treatment table. The radiation therapist will use the lines/dots on your skin and body mold or face mask to help you get into the right position.
  • You may see colored lights pointed at your skin marks. These lights are harmless and help the therapist position you for treatment.
  • You will need to stay very still so the radiation goes to the exact same place each time. You will get radiation for 1 to 5 minutes. During this time, you can breathe normally. Sometimes depending on the treatment location the therapists will instruct when to hold your breath and when you can breathe again.

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. The therapist watches you on a TV screen or through a window and talks with you through a speaker in the 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 will hear the radiation machine and see it moving around, but you won’t be able to feel, hear, see, or smell the radiation.

Most visits last from 30 minutes to an hour, with most of that time spent helping you get into the correct position.