Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is therapy using ionizing radiation, generally as part of cancer treatment to control or kill malignant cells. Radiation therapy kills cancer cells by damaging their DNA (the molecules inside cells that carry genetic information and pass it from one generation to the next). Radiation therapy can either damage DNA directly or create charged particles (free radicals) within the cells that can in turn damage the DNA.
Radiation therapy is a type of cancer treatment that uses beams of intense energy to kill cancer cells. Radiation therapy most often gets its power from X-rays, but the power can also come from protons or other types of energy.