Recent progress in the combination treatment of radiotherapy and PD-1/PD-L1 signaling blockade immunotherapy

Every stage of tumor initiation and development closely relates to immune regulation as tumor cells tend to evade attacks from immune system by employing the programmed death 1 (PD-1)/ programmed death-ligand 1 (PD-L1) interaction. Therefore, targeting the PD-1/PD-L1 pathway has become an attractive approach for cancer immunotherapy. Radiotherapy has long been considered a local tumor treatment modality and it is immune-inhibitory. However, accumulated evidence has shown that radiotherapy might enhance immune function by eliminating the tumor mass and has become a systemic tumor treatment modality. These observations indicate a strong rationale that the radiotherapy and anti-PD-1 and anti-PD-L1 immunotherapy may work synergistically to provide a powerful anti-tumor effect. This review discusses current progresses, challenges and perspectives of this novel combination treatment modality. Key words: Radiotherapy; PD-1/PD-L1 signal blockade; Oncology immunotherapy