Radiotherapy: The treatment of disease with ionizing radiation. Also called radiation therapy.
In radiotherapy, high-energy rays are often used to damage cancer cells and stop them from growing and dividing. A specialist in the radiation treatment of cancer is called a radiation oncologist.
Like surgery, radiation therapy is a local treatment; it affects cancer cells only in the treated area. Radiation can come from a machine (external radiation). It can also come from an implant (a small container of radioactive material) placed directly into or near the tumor (internal radiation). Some patients receive both kinds of radiation therapy.
External radiation therapy is usually given on an outpatient basis in a hospital or clinic, for example, 5 days a week for several weeks. Patients are not radioactive during or after the treatment.
For internal radiation therapy, the patient usually stays in the hospital for a few days. The radiation implant may be temporary or permanent. Because the level of radiation is highest during the hospital stay, patients may not be able to have visitors or may have visitors only for a short time. Once an implant is removed, there is no radioactivity in the body. The amount of radiation in a permanent implant goes down to a safe level before the patient leaves the hospital.
With radiation therapy, the side effects depend on the treatment dose and the part of the body that is treated. The most common side effects are tiredness, skin reactions (such as a rash or redness) in the treated area, and loss of appetite. Radiation therapy can also cause a decrease in the number of white blood cells, cells that help protect the body against infection. Although the side effects of radiation therapy can be unpleasant, they can usually be treated or controlled and, in most cases, they are not permanent.