KDR and osteosarcoma: In this study, we found that Apatinib combined with PD-1 inhibitor (Camrelizumab) seemed to have more advantages in prolonging PFS of osteosarcoma patients, this may be related to the VEGFR inhibitors improved immunotherapeutic activity of PD-1/PD-L1 antibodies by enhancing the tumor infiltration of immune cells and reducing the immunosuppressive effects of myeloid-derived suppressor cells (17), however, the risk of serious AEs is also increasing.