Radiation therapy has several benefits in the treatment of cancer: Kills Cancer Cells: Radiation therapy uses high-energy radiation to target and destroy cancer cells. It can be used alone or in combination with other treatments, such as chemotherapy or surgery, to kill cancer cells that may have spread to other parts of the body. Shrinks Tumors: Radiation therapy can also be used to shrink tumors before surgery, making it easier to remove them. It is also used after surgery for killing the remaining cancer cells.