For advanced pulmonary metastases or melanoma, radiotherapy combined with immune checkpoint inhibitor can block the immunosuppression pathway, enhance the antitumor immune response, and significantly improve survival. Stereotactic body radiation therapy (SBRT) delivers a large dose of radiation to the tumor target with high precision while sparing irradiation of the surrounding normal tissues. It is suggested that SBRT could be the most appropriate radiotherapy modality to be combined with immunotherapy since it induces the expression of a series of cytokines and immune molecules and is more likely to cause intense immune response and exert an abscopal effect than conventional radiotherapy. Previous studies have explored that total dose and fractionation seem to be important parameters for determining the immune response; the timing of radiation with immunotherapy significantly influences the outcome, and tumor infiltrating lymphocytes, the expression level of programmed death-ligand 1, and mismatch repair defect may be important predicators of the outcome. With appropriate radiotherapy dose and fractionation, the optimal timing of radiation with immunotherapy, and effective predictive markers, a combination of SBRT and immunotherapy may eliminate advanced malignancies while activating the systemic immune response to exert an abscopal effect.

Stereotactic body radiation therapy; Immunotherapy; Malignancy neoplasms