- A single treatment with radiation can improve the potency of immune-cell therapies. This is probably because the tumor tissue is damaged in a way that new tumor proteins are exposed, attracting immune cells to the tumor. By giving only a single dose of radiation, the immune cells that are attracted to the tumor are allowed to survive and function in their usual way, traveling throughout the body and educating other immune cells to recognize tumor, and to activate and expand in order to kill the tumor cells. Some research has shown that radiation may have a widespread effect on stimulating the immune system, educating immune cells to recognize and control tumors that have not been radiated.