Recent research progress of abscopal effect in tumor radiotherapy

If loosely defined, an abscopal effect occurs when localized irradiation affects the whole organism. In recent years, distant tumor regression and normal tissue damage after localized irradiation have been concerned by immuno-oncologists. However, the mechanisms of this effect are still far from clear. Mounting evidences suggest that the generation of abscopal effects is closely related to immune regulation. Radiotherapy might become a systemic tumor-treatment modality by enhancing immune function and played an important role in every stage of tumor development and prognosis. For the moment, targeting the immune checkpoint has become an attractive approach for malignant tumor therapy. Preclinical data have revealed that a strong abscopal effect could be effectively induced by the co-treatement of immune checkpoint inhibitors and irradiation, which could recruit antitumor T cells and achieve a powerful anti-tumor effect. This review discusses current progress and perspectives of abscopal effects in the combination of radiotherapy and immunotherapy. Key words: Abscopal effect; Radiotherapy; Tumor immunotherapy