759P Preconditioning with irradiation enhances efficacy of B7-H3-CAR-T in treating solid tumor models

Limited efficacy of CAR-T cells in treating solid tumors is largely due to the immunosuppression in the tumor microenvironment (TME). B7-H3 is expressed in most solid tumors including stromal fibroblasts and tumor blood vessels in TME. Radiotherapy has been found to alter TME in activating immuno-response, we tested and report the exploratory results of B7-H3-CAR-T in treating solid tumor models with preconditioning of radiotherapy.