Radiation therapy: MedlinePlus Medical Encyclopedia

P Radiation therapy uses high-powered x-rays, particles, or radioactive seeds to kill cancer cells.

T Information
P 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.
P 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
P TYPES OF RADIATION THERAPY
P 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. Newer methods provide more effective treatment with less tissue damage. These include:
- Intensity-modulated radiotherapy (IMRT)
- Image-guided radiotherapy (IGRT)
P Proton therapy is another kind of radiation used to treat cancer. Rather than using x-rays to destroy cancer cells, proton therapy uses a beam of special particles called protons. Because it causes less damage to healthy tissue, proton therapy is often used for cancers that are very close to critical parts of the body. It is only used for certain types of cancer.
P Internal beam radiation is placed inside 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.
P SIDE EFFECTS OF RADIATION THERAPY
P Radiation therapy can also damage or kill healthy cells. The death of healthy cells can lead to side effects.
P 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.
P Other side effects depend on the part of body receiving radiation:
- Abdomen
- Brain
- Breast
- Chest
- Mouth and neck
- Pelvic (between the hips)
- Prostate

T Alternative Names
P Radiotherapy; Cancer - radiation therapy; Radiation therapy - radioactive seeds; Intensity-modulated radiotherapy (IMRT); Image-guided radiotherapy (IGRT)

T Patient Instructions
- Stereotactic radiosurgery - discharge

T Images
- Radiation therapy

T References
P Doroshow JH. Approach to the patient with cancer. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 179.
P National Cancer Institute. Radiation therapy and you: support for people who have cancer. Updated May 2007. www.cancer.gov/cancertopics/coping/radiation-therapy-and-you. Accessed June 30, 2016.
P Zeman EM, Schreiber EC, Tepper JE. Basics of radiation therapy. In: Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff's Clinical Oncology. 5th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2014:chap 27.

T Review Date 5/20/2016
P Updated by: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

