Clinical trials of chimeric antigen receptor (CAR)-modified T cells have shown promise in hematologic malignancies. However, in solid tumors, the clinical responses have been less impressive. It is important to determine how to further improve the clinical effects of CAR-modified T cells. In this review, we focus on recent clinical trials and analyze the factors that determine clinical responses, including the following: 1) the composition of the CAR; 2) the preparation of CAR-modified T Cells; 3) the clinical treatment schedule; 4) the patient characteristics. We also propose future Strategies that must be investigated before the technology can be used in a wider range of clinical applications.