CAR T-cell expansion after CD19 CAR T-cell reinfusion. Measurements of CAR-modified T cells in peripheral blood by quantitative real-time PCR assay before CARTr and peak measurements in the 30 days after CARTr among patients with CR vs no response (NR) to CARTr for peripheral BCR (A), CD19⁺ hematogones (B), CD19⁺ MRD/relapse (C), and nonresponse to CARTi (D). P values compare peak measurements between CR and NR for each indication by the Wilcoxon rank sum test. Box-and-whisker plots show the median (horizontal line), IQR (box), and 1.5× the IQR (whiskers). Each observation is overlaid as a dot. Gray lines connect individual patient’s pre-CARTr measurement with his/her peak measurement. Data are only available for patients treated with CARTr on a clinical trial. PCR, polymerase chain reaction.