(Ionizing Radiation; Radiotherapy)
by Editorial Staff And Contributors
Radiation therapy is a treatment for cancer and other diseases. It uses high-energy particles to damage the genetic code (DNA) in the cancer cells. This makes the cells unable to grow or divide.
There are 2 main types of radiation therapy:
In certain cases, your doctor may recommend a combination of these. Radiation is often used with other types of treatment, such as surgery, chemotherapy, and immunotherapy (stimulates the immune system to fight infection).
This fact sheet will focus on external radiation therapy.
Reasons for Procedure TOP
This procedure may be done to:
Radiation therapy is commonly used to treat:
Possible Complications TOP
External radiation does not cause your body to become radioactive. It can cause side effects, as the radiation damages your own healthy cells as well as the cancer cells. Common side effects of radiation include, but are not limited to:
Discuss the specific side effects that you may have with your doctor.
Factors that may increase the risk of complications include:
A woman who is pregnant or could be pregnant should avoid exposure to radiation. It could harm a developing fetus.
What to Expect TOP
Prior to Procedure
You will go through a process called simulation. This takes between 30 minutes and 2 hours.
Description of the Procedure
You will be positioned on the treatment table or chair. The radiation therapist will leave the room and enter a control room. The machine will deliver radiation to certain areas of your body. The most common sources of radiation are x-rays, electron beams, and cobalt-60 gamma rays.
You must be still during treatment. The therapist can see you on a screen. You can talk with the therapist if you feel uncomfortable or sick.
How Long Will It Take? TOP
The treatment takes 1-5 minutes. You should allow at least 30 minutes for each session. Most treatments last 2-8 weeks. They are given once a day, 5 days per week. In some cases, you may be treated twice daily or only 3 times a week. Treatment schedules will depend on different factors. Talk to your radiation oncologist about the schedule planned for you.
Will It Hurt? TOP
Average Hospital Stay TOP
There is no hospital stay. External radiation is typically done at an office visit.
Post-procedure Care TOP
Be sure to follow your doctor’s instructions.
During treatment, your doctor will want to see you at least once a week. You may have routine blood tests to check for the effects of radiation on your blood cells.
After treatment is completed, you will have regular visits to monitor healing and to make sure the treatment affected the disease as planned. Follow-up care will vary for each person. Care may include further testing, medicine, or rehabilitative treatment.
Call Your Doctor TOP
After arriving home, contact your doctor if any of the following occur:
In case of an emergency, call for emergency medical services right away.
National Cancer Institute
OncoLink—Abramson Cancer Center at the University of Pennsylvania
Canadian Cancer Society
Cancer Care Ontario
Cancer treatment. Oncolink, University of Pennsylvania Cancer Center website. Available at:
...(Click grey area to select URL)
Accessed February 24, 2015.
Radiation therapy for cancer. National Cancer Institute website. Available at:
...(Click grey area to select URL)
Accessed June 17, 2008.
Last reviewed February 2015 by Igor Puzanov, MD
Last Updated: 3/18/2013