ABSTRACT Chimeric antigen receptor T cells (CAR‐T) have been associated with prolonged hematotoxicity known as late immune effector cell‐associated hematologic toxicity (ICAHT), but there is limited literature on its duration and clinical implications. We conducted a retrospective review of 156 adults who received CD19‐directed CAR‐T therapy at The Ottawa Hospital between 2019 and 2024. Late ICAHT occurred in 39% (95% CI 31%–47%) of recipients, with a duration ranging from 6 to 1473 days. Cumulative incidence analysis, censoring for disease progression and death, yielded a median duration of 183 days, with 20% (95% CI 11%–38%) experiencing ICAHT lasting over 1 year. Overall survival was comparable between patients with and without late ICAHT. In univariate analysis, HEMATOTOX score was significantly associated with the development of late ICAHT. Among a subset of 13 patients assessed for resource utilization, growth factors were the primary cost driver. Patients required frequent follow‐up, with a median of 1 in every 7 days involving an in‐person healthcare encounter. Late ICAHT was a common but usually self‐limited toxicity. The 30‐day cutoff currently used to define late ICAHT should be compared to later cutoffs to evaluate whether it improves the characterization of ICAHT's clinical impact on outcomes and healthcare utilization.
Giguère et al. (Fri,) studied this question.