Understanding Radiation Therapy

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How is radiation therapy given?

Radiation therapy can be given in 3 ways: as external radiation, as internal radiation, or as systemic radiation. In some cases more than one type is used.

External radiation (or external beam radiation) uses a machine that directs high-energy rays from outside the body into the tumor and some normal nearby tissue. Most people get external radiation therapy over many weeks. It’s done during outpatient visits to a hospital or treatment center.

Internal radiation (also called brachytherapy [brake-ee-THER-uh-pee]) uses a radioactive source in the form of a wire, seed, pellet, or balloon that’s called an implant. The implant is put inside the body in or near the tumor. The radiation from the implant travels only a short distance, so it has very little effect on normal body tissues. In some cases, patients may need to stay in the hospital while getting internal radiation.

Sometimes, after a tumor has been removed by surgery, radioactive implants are put into the area where the tumor was to kill any cancer cells that may still be there.

Implants may either be left in the patient as a permanent implant or they may be removed after a certain amount of time.

Systemic radiation is given using radiopharmaceuticals (ray-dee-o-farm-uh-SUIT-uh-kulls), which are radioactive drugs used to treat certain types of cancer. These drugs are unsealed radioactive sources that can be given by mouth or put into a vein; they then travel throughout the body. Treatment with radiopharmaceuticals often requires a short stay in the hospital.

Deciding which type of radiation to use depends on the kind of cancer you have and where it is in your body.

The different types of radiation therapy are described in more detail in the next sections.


Last Medical Review: 01/24/2013
Last Revised: 01/24/2013