Radiation treatment or radiotherapy refers to the use of high-energy X-radiation or other particles as part of a cancer treatment to control or to kill malignant (cancer) cells. It works by damaging the DNA of cancer cells by ionizing the atoms that make up the DNA chain, breaking atomic and molecular bonds, and generation of double-strand breaks in DNA is considered the factor that causes cell death. It is generally delivered by a linear accelerator. To spare normal tissue, shaped radiation beams are pointed from different angles to cross at the tumor, which absorbs a much larger dose than the surrounding tissue.
Radiotherapy can be used alone or, more often, combined with other cancer treatments like chemotherapy or surgery, for a wide range of cancers to maximize tumor control and to deliver a better quality of life, minimizing side effects, reducing toxicity and preserving the organs.
In several settings radiotherapy may be a curative treatment, especially when a tumor is confined to a single area of the body. It is also used before or after a surgery to reduce the probability of microscopic disease left after treatment.
The duration of radiation treatment is variable depending on the type of cancer and its extension, and it can go from one single session to eight weeks of daily irradiation. The technique, dose, expected outcomes and related toxicities vary depending on diagnosis and area treated.