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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.


The week before your treatment:

  • Arrange a ride home. Ask a family member or friend to drive you home after your surgery or procedure. Do not drive yourself home.
  • Tests: You may need x-rays, a CT scan, MRI, or ultrasound to check the location, shape, and size of your tumor. Ask your healthcare provider for more information about these and other tests that you may need. Write down the date, time, and location of each test.
  • Write down the correct date, time, and location of your surgery.

The night before your treatment:

Ask healthcare providers about directions for eating and drinking.

The day of your treatment:

  • You or a close family member will be asked to sign a legal document called a consent form. It gives healthcare providers permission to do the procedure or surgery. It also explains the problems that may happen, and your choices. Make sure all your questions are answered before you sign this form.
  • Ask your healthcare provider if you need to stop using aspirin or any other prescribed or over-the-counter medicine before your procedure or surgery.
  • Bring your medicine bottles or a list of your medicines when you see your healthcare provider. Tell your provider if you are allergic to any medicine. Tell your provider if you use any herbs, food supplements, or over-the-counter medicine.


What will happen:

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. This will help prevent healthy tissue from getting radiation. 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.


  • You cannot make it to your treatment on time.
  • You have a fever.

Seek Care Immediately if

  • You have a seizure.
  • You suddenly have problems remembering things.
  • You have sudden chest pain or shortness of breath.


  • 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.

Care Agreement

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.

Ā© Copyright IBM Corporation 2018 Information is for End User's use only and may not be sold, redistributed or otherwise used for commercial purposes. All illustrations and images included in CareNotesĀ® are the copyrighted property of A.D.A.M., Inc. or IBM Watson Health

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 (Precare)

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