What Is Radiation Exactly?

Radiation therapy uses high-energy particles or waves, such as X-rays, gamma rays, electron beams, or protons to kill cancer cells.

Radiation is the energy that comes from a source and travels through space at the speed of light in the form of waves (electromagnetic radiation) or particles (particulate radiation). Radiation can be in the form of heat, sound, or light.

In medicine, radiation therapy is used as a cancer treatment to destroy or damage cancer cells. Cancer cells grow abnormally and out of control and can destroy the body’s healthy cells. Radiation therapy uses high-energy particles or waves, such as X-rays, gamma rays, electron beams, or protons to kill cancer cells. 

Radiation therapy is used to treat many different types of cancer either alone or in combination with other treatments. The goals of radiation therapy include:

• To cure or shrink early-stage cancer
  • Used before surgery to shrink a tumor (pre-operative therapy or neoadjuvant therapy)
  • Used after surgery to help keep cancer from returning (adjuvant therapy)
• To stop cancer from coming back (recurring) in another part of the body
• To treat symptoms caused by advanced cancer (palliative radiation)
• To treat recurrent cancer 

The type of radiation given depends on the type of cancer being treated and its location. Sometimes more than one type of radiation therapy is used.

Radiation therapy is given in three different ways:

• External radiation (external beam radiation)
  • A machine directs high-energy rays from outside the body into the tumor
  • Involves outpatient visits to a hospital or treatment center 
  • Usually given over several weeks and may be given twice a day for several weeks
• Internal radiation (brachytherapy)
  • A radioactive source is put inside the body into or near the tumor
  • It may be temporary or permanent, depending on the cancer
  • For permanent or long-term brachytherapy, the person may be radioactive for a period of time and may need to follow special safety precautions 
• Systemic radiation
  • Radioactive drugs are administered orally or intravenously (IV) to pass throughout the body