B-cell aplasia and clinical response following CAR19. (A) Time-to-event analysis for recovery of CD19⁺ B cells detectable by flow cytometry performed on peripheral blood showed a significantly longer duration of B-cell aplasia in those patients who maintained a durable response to axi-cel. Patients were censored at the time of last follow-up; disease relapse or progression and death were considered competing events. Analysis was performed using the K-M method. (B) When patients who developed disease relapse or progression were stratified as CD19⁺ or CD19⁻ status at relapse by immunohistochemistry or flow cytometry performed on lymphoma cells, there was no significant difference between the duration of B-cell aplasia observed. CD19 status at the time of relapse was available for 18 of 21 (85.7%) patients. (C) The proportion of patients with detectable B cells at each assessment time point, stratified by clinical response. The number of patients who underwent testing (N) is shown by time point below the plot. (D) Correlations between the duration of B-cell aplasia and the durations of other concurrent severe cytopenias; only noncensored durations from time-to-event analysis were included. Lines represent linear regression using least-squares fitting. P values shown were obtained by the likelihood ratio test computed using Cox proportional-hazards regression of the time-to-event variable vs the factor defining the 2 groups (A-B) and Spearman’s correlation analysis (D).