Sworder and colleagues investigated the utility of ctDNA analysis in investigating the determinants of resistance to CD19-targeted engineered T-cell therapies by an innovative simultaneous tumor and effector profiling (STEP) approach, which allows the capture of the tumor ctDNA and effector T-cell cfDNA from the same plasma sample to enable evaluation of both the lymphoma and the CAR-T cells. This evidence concerns the gene CD19 and neoplasm.