Internal Radiation Therapy



Radiation therapy (RT) treats cancer and other diseases. It uses high-energy particles. These break the DNA in the cancer cells. The cells can’t grow or split after RT.

There are 2 main types of RT:

  • External — A machine sends radiation. It aims it at cells from outside the body.
  • Internal— Radioactive materials are placed in the body near the cells.

You doctor may want to use both. Surgery, chemotherapy , and therapy to spark the immune system to fight infection may also be used.

This fact sheet will focus on internal RT.

Possible Complications

Internal RT does not cause your body to become radioactive. It can cause side effects. The RT harms healthy cells and cancer cells.

Here are some problems you may have:

  • Feeling very tired
  • Skin changes such as redness and irritation
  • Reduced white blood cell count
  • Hair loss
  • Nausea, vomiting, or diarrhea
  • Lack of hunger

Talk to your doctor about the problems you may have.

Other things that may raise the risk of problems are:

  • Prior RT or chemotherapy
  • If you have had lupus , scleroderma , or dermatomyositis

You should not be around radiation if you are pregnant or could be pregnant. It could harm the growing fetus.



This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

Edits to original content made by Denver Health.

a (Ionizing Radiation; Radiotherapy; Brachytherapy)


American Cancer Society 

Radiology Info—Radiological Society of North America 


Canadian Association of Radiologists 

Canadian Cancer Society 


Bracytherapy. Radiological Society of North America Radiology Info website. Available at: Accessed January 28, 2021.

Radiation. Oncolink, University of Pennsylvania Cancer Center website. Available at: Accessed January 28, 2021.

Radiation therapy. American Cancer Society website. Available at: Accessed January 28, 2021.

Radiation therapy for cancer. National Cancer Institute website. Available at: Accessed January 28, 2021.