The involvement of the immune system is supported by the finding that the combination of radiation with immune system-boosting drugs, such as the anti-PD-1 (MEDI0680) or anti-CTLA-4 (AGEN1884) monoclonal antibodies, led to a reduction of the size of a metastatic nonirradiated tumor and of cancer spread in the body. Here, CTLA4 is linked to neoplasm.