The external radiation technique involves guiding the high-energy radiation onto the tumor from a source situated outside the body. While delivering the radiation, the machine moves around the patient's body without touching it. It kills cancer cells by damaging their DNA through heat generation.
Radiation therapy may be delivered alone or with other treatments, such as chemotherapy and surgery. It is used before the surgery to shrink the tumor and after the surgery to kill the remaining cancer cells. It is also used when surgery is not viable. Further, in advanced-stage cancer, it is used to provide relief from cancer symptoms.
Stereotactic radiosurgery delivers large doses on a single day, while stereotactic radiation therapy delivers small doses during multiple sessions.