Introduction to Radiation Therapy

Radiation therapy can be used alone or in combination with other therapies to kill cancer and can be given in several different ways. The types of radiation therapy include:

  • External beam (external radiation therapy)
  • Brachytherapy (internal radiation therapy)
  • Radiopharmaceuticals (systemic radiation therapy)

External Beam Radiation

In external beam radiation, the most widely used type of radiation therapy, a machine called a linear accelerator delivers treatment. External beam radiation is used to treat large areas of the body or more than one area at the same time. Each treatment session feels like getting a long X-ray. Treatments are usually given daily over several weeks in an outpatient clinic. 

There are many kinds of external beam therapy, with an alphabet soup of names from IMRT and VMAT to SBRT and IGRT. Your doctor will explain which technique is recommended for you and how it works.


Brachytherapy literally means "short-distance therapy." It involves placing a source of radiation directly into or near the area that needs treatment. This internal treatment delivers a high dose of radiation to a small area in a fairly short period of time with less damage to healthy tissue.


Radiopharmaceuticals are drugs that contain some radioactive materials and are taken by mouth or injected into a vein. They can act as a "magic bullet" to deliver radioactivity to a tumor site while sparing most of the surrounding tissue. Because this process introduces a radioactive substance into your body, some radiation will remain in your system for a few days. Your doctor will have you follow special short-term precautions to protect yourself and others from the effects of this radiation.

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