Radiation therapy is a form of cancer treatment that uses an intense form of energy, called ionizing radiation, to damage or destroy cancer cells. Because cancer cells grow and divide more rapidly than normal cells , radiation therapy can successfully treat many kinds of cancer.
Normal cells are also affected but recover from the effects of radiation. To protect normal cells, radiation therapists carefully limit radiation doses and sequence the treatments over time. They also shield as much normal tissue as possible as they target the radiation at the site of the cancer.
External beam radiotherapy uses machines to focus radiation on a cancer site. Depending on the amount of energy it possesses, the radiation can be used to destroy cancer cells both on the surface and deeper in the body. The higher the energy of the beam, the deeper the radiation can penetrate into the target tissue.
Internal radiotherapy, or brachytherapy, places radioactive implants directly in a tumour or body cavity. In this treatment, the radiation dose is concentrated in a small area.