It is commonly prescribed to patients whose cancer is not localized but may have metastasized or spread to various locations in the body. Chemotherapy can be used to reduce symptoms and pain associated with cancer as well as to slow the growth of cancerous tumors. In some circumstances, chemotherapy can even kill spreading cancer cells. Radiotherapy is a method of treating cancer that uses radiation energy. Radiation therapy is most often used to treat localized cancers, as opposed to cancers that have spread throughout the body. The goal of radiation therapy is to kill cancer cells or at least limit their ability to grow and divide by damaging their genetic material. Like chemotherapy, radiation therapy does not target cancer cells with perfect precision, and some normal, healthy cells may also be damaged. There are also surgical operations that surgeons specialize in tumors