Radiation therapy

Synonyms: X-ray therapy (XRT)

Medical Specialties: Oncology

Clinical Definition

Radiation therapy uses high-energy radiation to damage or alter cellular DNA in order to treat malignancies or disease. Once genetic material in cancer cells is damaged, cells are unable to divide, and tumors shrink or may be eradicated. The dose of radiation given will vary based on the malignancy and specific site treated. 

In Our Own Words

About 50 percent of all cancer patients get radiation therapy in some form, at some point, during treatment. Medical experts may administer radioactive substances to the body via implants, specialized external machines, X-rays, gamma rays or even high-energy particles, which deliver planned doses of radiation to a particular location in the body.


The most common type of radiation therapy is external beam radiation used to treat a variety of cancers including those of the lung, head and neck. Radiation therapy is often prescribed in short doses administered daily over the course of several weeks. Some patients are treated using radiation alone while others receive radiation along with chemotherapy.

Relevant Conditions
Common Types
  • External beam RT
Side Effects
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  • National Cancer Institute, “Dictionary of Cancer Terms.” http://www.cancer.gov. Accessed July 2013.
  • American Cancer Society. “Understanding Radiation Therapy” 2012. http://www.cancer.org. Accessed July 2013.
  • National Cancer Institute. “What is Radiation Therapy for Cancer?” http://www.cancer.gov. Accessed July 2013.
  • Cleveland Clinic. “What is Radiation Therapy?” http://my.clevelandclinic.org. Accessed July 2013.
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