Association of busulfan area under the curve with the development of neurotoxicity in children and adolescents receiving busulfan-containing conditioning regimens for stem cell transplantation.

Although several studies suggest that higher busulfan exposure is associated with neurotoxicity, research on the relevance of pharmacokinetic parameters is limited. The aim of this study was to explore the impact of busulfan area under the concentration-time curve (AUC) on the development of neurological complications in children and adolescents receiving busulfan-containing conditioning regimens. Patients aged 0-20 years who received a busulfan-based regimen at our hospital between June 2017 and May 2024 were analyzed. The primary outcome measure was the incidence of neurological complications within 7 days of starting busulfan. A total of 36 consecutive patients were analyzed. Median busulfan AUC across 96 h (AUC96) was 86.3 (interquartile range 73.6-100.8) mg × h/L. Overall, 13 (36%) patients developed neurological complications, including 2 patients with grade 3 seizures. The AUC96 cut-off value was set at 80.0 mg × h/L (sensitivity 85%, specificity 57%, area under the receiver-operating characteristic curve 0.71). A higher incidence of neurological complications was observed in the AUC96 > 80.0 mg × h/L group than in the AUC96 ≤ 80.0 mg × h/L group (50% vs. 14%, P = 0.033). These results suggest that a higher busulfan AUC96 may be associated with an increased risk of neurological complications.