Radiation therapy uses high-powered x-rays, particles, or radioactive seeds to kill cancer cells.
Cancer cells multiply faster than normal cells in the body. Because radiation is most harmful to quickly growing cells, radiation therapy damages cancer cells more than normal cells. This prevents the cancer cells from growing and dividing, and leads to cell death.
Radiation therapy is used to fight many types of cancer. Sometimes, radiation is the only treatment needed. It may also be used to:
Shrink a tumor as much as possible before surgery
Help prevent the cancer from coming back after surgery or chemotherapy
Relieve symptoms caused by a tumor
Treat cancers that cannot be removed with surgery
TYPES OF RADIATION THERAPY
External beam radiation is the most common form. This method carefully aims high-powered x-rays or particles directly at the tumor from outside of the body.
Internal beam radiation is placed inside of your body.
One method uses radioactive seeds that are placed directly into or near the tumor. This method is called brachytherapy, and is used to treat prostate cancer. It is used less often to treat breast, cervical, lung, and other cancers.
Another method involves receiving radiation by drinking it, swallowing a pill, or through an IV. Liquid radiation travels throughout your body, seeking out and killing cancer cells. Thyroid cancer may be treated this way.
SIDE EFFECTS OF RADIATION THERAPY
Radiation therapy can also damage or kill healthy cells. The death of healthy cells can lead to side effects.
These side effects depend on the dose of radiation, and how often you have the therapy. External beam radiation may cause skin changes, such as hair loss, red or burning skin, thinning of skin tissue, or even shedding of the outer layer of skin.
Other side effects depend on the part of body receiving radiation:
Zemen EM, Schreiber EC, Tepper JE. Basics of radiation therapy. In: Niederhuber JE, Armitage JO, Doroshow JH, et al., eds. Abeloff's Clinical Oncology. 5th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2013:chap 27.
National Cancer Institute. Radiation therapy and you: support for people who have cancer. Available at: http://www.cancer.gov/cancertopics/coping/radiation-therapy-and-you. Accessed May 29, 2014.
Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.