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/mm 3 ) and Day 10 for tisa‐cel (median 8.1%; 33.2 cells/mm 3 ). 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.