Harnessing Ionizing Radiation to Enhance Immunotherapy: A Paradigm Shift

The field of cancer immunotherapy, once the sole purview of immunology, has evolved toward the harnessing of newly described properties of ionizing radiation (IR). Cancer immunotherapy now includes the combination of established cytotoxic modalities with immune manipulations, as vaccines alone are unlikely to succeed at curing bulky, established tumors.[1] Combining chemotherapy with immunotherapy has shown promise, despite the fact that both are systemic modalities with overlapping effects.[2-4] In this regard, radiotherapy has a clear advantage, as its effects can be targeted to the primary tumor, converting the tumor itself into an “immunologic hub” ideally capable of subverting the immune defeat that has resulted in the clinical presentation of cancer. This approach is appealing since most immune impairment appears to occur at the tumor site.[5]