Research progress on SBRT combined with ICIs in the treatment of solid tumors

Abstract

Stereotactic Body Radiotherapy (SBRT) is a precise radiotherapy technique characterized by the delivery of high-dose radiation to limited tumor targets within a small number of fractions, and has been shown to achieve effective local tumor control in several solid tumors. These factors, particularly an immunosuppressive Tumor Microenvironment (TME), may limit the therapeutic efficacy of PD-1 inhibitors. The combination of SBRT and PD-1 blockade has shown potential benefits in improving tumor response, local control, and progression-free survival in selected patients; however, systemic antitumor responses remain inconsistent and need further validation. Mechanistically, this strategy is biologically plausible because SBRT can induce tumor cell death, facilitate tumor antigen release, activate dendritic cells, and promote cytotoxic T-cell infiltration. However, this combined strategy is still not fully standardized because existing studies differ in tumor type, radiation dose, fractionation schedule, treatment sequence, irradiated target selection, and biomarker evaluation. This review provides an overview of the underlying mechanisms, clinical evidence, safety profiles, current limitations, and future perspectives regarding the combination of SBRT and Immune Checkpoint Inhibitors (ICIs) in solid tumor therapy.