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External Radiation Therapy


External radiation therapy is a treatment that uses radiation (x-ray energy) to kill cancer cells. Radiation is a strong beam of x-ray energy that passes through organs and healthy tissue to reach tumors. External radiation therapy is used to shrink the tumor or kill the cancer cells. It may also be used to decrease symptoms caused by the tumor. External radiation therapy may be combined with other treatments such as medicine, chemotherapy, or surgery.


Before your treatment:

  • Informed consent is a legal document that explains the tests, treatments, or procedures that you may need. Informed consent means you understand what will be done and can make decisions about what you want. You give your permission when you sign the consent form. You can have someone sign this form for you if you are not able to sign it. You have the right to understand your medical care in words you know. Before you sign the consent form, understand the risks and benefits of what will be done. Make sure all your questions are answered.
  • Tests:
    • Blood tests: These may be done to check your blood count or to check the function of your organs.
    • Ultrasound: An ultrasound uses sound waves to show pictures on a monitor. An ultrasound may be done to show the size, shape, and location of your tumor.
    • CT scan: This test is also called a CAT scan. An x-ray machine uses a computer to take pictures of your body. The pictures may show the size, shape, and location of the tumor. You may be given a dye before the pictures are taken to help healthcare providers see the pictures better. Tell the healthcare provider if you have ever had an allergic reaction to contrast dye.
    • MRI: This scan uses powerful magnets and a computer to take pictures of your body. An MRI used to check around your tumor for other problems. You may be given dye to help the pictures show up better. Tell the healthcare provider if you have ever had an allergic reaction to contrast dye. Do not enter the MRI room with anything metal. Metal can cause serious injury. Tell the healthcare provider if you have any metal in or on your body.

During your treatment:

A MRI or CT scan is used to help point the radiation beam at your tumor. The scan will also show the exact shape, size, and location of your tumor. Shields to block radiation from other parts of your body may be put over you. Your healthcare provider will set the beam's shape and how much radiation your tumor will get. The beam is pointed so that it passes through the least amount of healthy tissue. The size and shape of the beam may be the same as your tumor, or it may be larger. During your treatment you will need to lie still and relax. You should not feel any pain, heat, or tingling during treatment.

After your treatment:

You may be taken to a room where healthcare providers will monitor you closely for problems. Do not try to get out of bed until your healthcare provider says it is okay. Later, you may be able to go home, or you will be taken to your hospital room.


  • Radiation kills cancer cells, but can also damage healthy cells. You may have nausea, vomiting, diarrhea, or blood in your bowel movements. After treatment, you may feel more tired, weak, or have an increased risk of infection. External radiation therapy may cause your skin to be dry, red, or darker than usual. You may get sores on your skin. You may have thinning or loss of hair. Organs close to where the radiation is aimed may be harmed and not work as well, or stop working completely. You may become infertile after radiation treatment. Radiation increases the risk of a second type of cancer.
  • Without external radiation therapy, tumors can grow and damage tissues around them. You may get weak, lose weight, and have pain in areas with tumors. Cancer cells may spread and grow into new tumors in other parts of your body. These tumors can damage more organs and make it hard for you to heal. You may not be able to do things that you enjoy doing.


You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your healthcare providers to decide what care you want to receive. You always have the right to refuse treatment.

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The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Learn more about External Radiation Therapy (Inpatient Care)

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