• Radiation Therapy—External

    (Ionizing Radiation; Radiotherapy)


    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:
    • External—radiation is delivered by a machine that shoots particles at the cells from outside the body
    • Internal—radioactive materials are placed in the body near the cancer cells (also called implant radiation or brachytherapy)
    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

    This procedure may be done to:
    • Control the growth or spread of cancer
    • Attempt to cure cancer
    • Reduce pain or other symptoms caused by cancer—palliative radiation
    Radiation therapy is commonly used to treat:

    Possible Complications

    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:
    • Fatigue
    • Skin changes (redness, irritation)
    • Reduced white blood cell count
    • Hair loss
    • Nausea, vomiting, or diarrhea
    • Appetite loss
    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

    Prior to Procedure

    You will go through a process called simulation. This takes between 30 minutes and 2 hours.
    • You will lie on an exam table. A CT scan will be used to define the exact place(s) where radiation will be directed. The exact area on your skin may be marked with colored ink. You may also have a small tattoo (or several) placed on your skin. This is as a permanent mark to help aim the radiation beam.
    • Depending on the type of treatment required, you may also be measured for devices like braces that will help you stay still during treatment.

    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.
    External Radiation of a Tumor
    Radiation of Tumor
    Copyright © Nucleus Medical Media, Inc.

    How Long Will It Take?

    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?


    Average Hospital Stay

    There is no hospital stay. External radiation is typically done at an office visit.

    Post-procedure Care

    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, medications, or rehabilitative treatment.

    Call Your Doctor

    After arriving home, contact your doctor if any of the following occur:
    • Signs of infection, including fever and chills
    • Diarrhea or loss of appetite
    • Unexplained weight loss
    • Frequent urination, particularly if it is associated with pain or burning sensation
    • New or unusual swelling or lumps
    • Nausea and/or vomiting that you cannot control with the medications you were given
    • Pain that does not go away
    • Unusual changes in skin, including bruises, rashes, discharge, or bleeding
    • Cough, shortness of breath, or chest pain
    • Any other symptom your nurse or doctor told you to look for
    • Any new or unexpected symptoms
    If you think you have an emergency, call for emergency medical services right away.


    American Cancer Society http://www.cancer.org

    National Cancer Institute http://www.cancer.gov


    Canadian Cancer Society http://www.cancer.ca

    Cancer Care Ontario http://www.cancercare.on.ca


    Radiation. Oncolink, University of Pennsylvania Cancer Center website. Available at: http://www.oncolink.org/treatment/treatment.cfm?c=5. Accessed February 24, 2015.

    Radiation therapy for cancer. National Cancer Institute website. Available at: http://www.cancer.gov/about-cancer/treatment/types/radiation-therapy/radiation-fact-sheet. Accessed February 24, 2015.

    Revision Information

    • Reviewer: EBSCO Medical Review Board Mohei Abouzied, MD
    • Review Date: 03/2017
    • Update Date: 03/18/2013
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