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Quick Facts

Radiation Therapy


The Manual's Editorial Staff

Last full review/revision Jul 2021| Content last modified Jul 2021
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What is radiation therapy?

Radiation therapy is a cancer treatment that uses beams of radiation to destroy cancer cells and shrink cancer tumors.

  • Doctors use radiation to treat many types of cancer, including head, neck, brain, and breast cancer

  • Radiation may not destroy all the cancer cells and may destroy some normal cells, which can cause some side effects

  • Doctors may treat your cancer with radiation and another type of cancer treatment, such as chemotherapy

  • Radiation therapy may raise your chances of getting other cancers in the future

Radiation therapy kills all kinds of cells in your body, not just cancer cells. The radiation has to be aimed very carefully so that it hits mainly the cancer and not healthy tissue.

Types of radiation therapy

Most radiation therapy uses a machine that sends a beam of radiation to the part of your body that has cancer. There are two kinds of radiation beams:

  • Gamma rays

  • Proton beams

Proton beams can be aimed more precisely than gamma rays. Whatever kind of beam is used, most people get radiation therapy every day for 6 to 8 weeks.

  • Doctors often use MRI, CT scan, and ultrasound during radiation therapy to be able to aim the radiation beam more precisely onto the tumor

Another way doctors avoid harming healthy tissue is to shoot the radiation beam at your cancer from different sides of your body and at different angles. That way, the beam always hits the cancer, but the same healthy tissue doesn't get hit each time.

Other types of radiation therapy include:

  • A radioactive substance that doctors inject into your vein that travels through your blood to the cancer cells

  • Small radioactive pellets (seeds) that doctors place into the cancer tumor

What are the side effects of radiation therapy?

  • Feeling weak and tired

  • Mouth sores

  • Skin problems, such as redness, itching, and peeling

  • Pain when you swallow

  • Swelling in your lungs

  • Feeling sick to your stomach or throwing up

  • Feeling like you need to urinate (pee) more than usual or having pain when urinating

  • Bruising easily

Radiation therapy can damage normal tissue and gives you a higher chance of developing other cancers in the future. The risk depends on your age and where in your body you get radiation therapy.

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