The combined use of stereotactic body radiotherapy (SBRT) and immunotherapy is a promising new development. However, the optimal modality for combining SBRT with immunotherapy needs further study. Timmerman and colleagues reported that the time split between radiotherapy and α-PD-L1 therapy can affect the therapeutic effect and introduced a new SBRT paradigm-personalized ultrafractionated stereotactic adaptive radiation therapy (PULSAR). Split-course SBRT based on systemic therapy (3S), which is a concept similar to PULSAR, was introduced. We focus on the underlying mechanisms and advantages of PULSAR or 3S. Notably, the partial results of two relevant clinical trials initiated by our clinical research center are reported here. Moreover, some directions that warrant further investigation are emphasized.