Routine Monitoring of CAR‐T‐Cells Expansion and Persistence in Patients With Aggressive Large B‐Cell Lymphoma by Flow Cytometry: A Single‐Center Experience

This retrospective, single-center study evaluated routine flow cytometry (FC) monitoring of CAR-T-cells in 45 patients with aggressive large B-cell lymphoma (LBCL). CAR-T-cells expansion was assessed from Day 0 to Month 12. Peak expansion occurred on Day 7 after axi-cel (median 39.3% of total lymphocytes; 87 cells/mm³) and Day 10 for tisa-cel (median 8.1%; 33.2 cells/mm³). Greater CAR-T-cells expansion was associated with immune-related toxicity, with median peak levels reaching 52.8% in patients with grade 2 cytokine release syndrome (CRS) versus 6.6% in those without (p < 0.001) and 60.8% in patients with immune effector cell-associated neurotoxicity syndrome (ICANS) versus 15.3% in those without (p < 0.001). Prolonged cytopenia was observed in 65% of patients and more frequently among those with greater CAR-T-cells expansion. This study highlights FC as a practical tool for monitoring CAR-T-cells dynamics in routine practice, with potential implications for early toxicity risk assessment and personalized supportive care.