What is Radiation Therapy—External?

Radiation therapy is a treatment of 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 two 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.

• Control the growth or spread of cancer

• Attempt to cure cancer

• Reduce pain or other symptoms caused by cancer (This is called palliative radiation.)

Radiation therapy is commonly used to treat:

• Solid tumors such as prostate cancer, breast cancer, and head and neck cancers
• Lymphomas and leukemia

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:

• Previous radiation therapy
• A personal history of lupus , scleroderma , or dermatomyositis

A woman who is pregnant or could be pregnant should avoid exposure to radiation. It could harm a developing fetus.

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