The timing of concurrent intrathecal chemotherapy during blinatumomab infusion influences neurotoxicity in pediatric acute lymphoblastic leukemia.

Objective: To assess the safety profile of administering intrathecal (IT) chemotherapy concurrently with blinatumomab in pediatric patients with acute lymphoblastic leukemia (ALL). Methods: This retrospective analysis included 93 pediatric ALL patients treated between February 2021 and May 2025 who received blinatumomab. Results: Of the 93 enrolled patients (median [Q1, Q3] age, 6 [4, 12] years), 42 (45%) were given IT chemotherapy concurrently, while the remaining 51 (55%) served as controls. Neurotoxic events occurred in eight patients (8.8%) overall, with no statistically significant difference between the concurrent IT and control groups (12% vs. 6%, p = 0.461). However, receiving IT chemotherapy on Day 1 of blinatumomab was strongly associated with neurotoxicity (OR = 15.6; 95% CI: 2.96-87.8; p = 0.001). Additional univariate predictors included CD4+ T-cell count (OR = 0.03; 95% CI: 0.00-0.50; p = 0.045), serum albumin (OR = 1.17; 95% CI: 1.02-1.39; p = 0.042), and bone marrow blast percentage (OR = 1.05; 95% CI: 1.01-1.09; p = 0.017). Multivariate analysis identified Day 1 concurrent IT administration as an independent risk factor (OR = 12.5; 95% CI: 1.45-131; p = 0.023). Conclusions: Initiating IT chemotherapy on the same day as blinatumomab infusion significantly increases the risk of neurotoxicity in pediatric ALL patients.