Radiation oncology is a branch of medicine that treats cancer by using high-energy radiation in the form of photons (such as x-rays or gamma rays) or subatomic particles (such as electrons or protons). According to the American Cancer Society about 60 percent of people with cancer receive radiation therapy. Radiation therapy may be used as the primary treatment for some forms of cancer; as an “adjuvant” therapy to reduce the risk that cancer will recur; or as a “palliative” therapy to reduce symptoms caused by a tumor.

How Radiation Therapy Works
Radiation therapy (also called radiotherapy) works by damaging the DNA inside the cancer cells. When the DNA sustains enough damage, the cells cannot multiply, and they die. The goal of radiation therapy is to destroy as many cancer cells as possible with the least damage to healthy cells.

Why Radiation Therapy Is Used
The exact role of radiation therapy in your care depends on many factors, including the type, size, location and stage of your cancer. Radiation therapy may be used as any of these:

  • Primary treatment. This means it’s the main treatment you receive to cure, stop or slow the disease.
  • Adjuvant therapy. This means you receive it after other treatments, like surgery and chemotherapy, to reduce the risk that your cancer will come back.
  • Palliative therapy. This means it’s used to relieve symptoms, like pain, by shrinking your tumor.