Radiation Therapy and Immunotherapy—A Potential Combination in Cancer Treatment

Background: Radiation therapy (RT) is a longstanding treatment modality for cancer. In addition, immune checkpoint blockade has been a significant development in the field of immunotherapy, modifying key immunosuppressive pathways of cancer cells. Methods: The aim of the present work was to review current concepts of RT and immunotherapy synergism, the abscopal effect, and the molecular effects of RT in the tumour microenvironment, its influence on immune stimulation, and potential clinical outcomes that might evolve from ongoing studies. We also discuss potential predictors of clinical response. Results: Up-to-date literature concerning the mechanisms, interactions, and latest knowledge about RT and immunotherapy was reviewed and summarized, and is presented here. Conclusions: The possibility of using hyperfractionated RT to combine an abscopal effect with the enhanced effect of immune treatment using checkpoint blockade is a very promising method for future tumour treatments.