Greater numbers of CAR T cells were associated with lower serum concentrations of cytokines strongly correlated with severity. Peak serum MCP-1 (A), soluble IL-2Rα (B), and IL-6 (C) concentrations (log10 pg/µL) in patients who received 2 × 10⁶ CAR T cells per kilogram and Cy/Flu lymphodepletion (Con-ibr, n = 18; No-ibr, n = 18). Bold horizontal lines represent the median, the box represents the IQR, and the vertical lines represent quartiles ± 1.5 × IQR. Two patients who died before the peak of CAR T-cell expansion were excluded. The P values were calculated using the Wilcoxon rank-sum test (2-sided) and were adjusted for multiple comparisons using the Benjamini-Hochberg procedure. No-ibr, ibrutinib discontinued prior to lymphodepletion.