AbstractBackgroundAlthough corticosteroids remain a mainstay of treatment for acute lymphoblastic leukemia (ALL), they can cause troublesome neurobehavioral changes during active treatment, especially in young children. We evaluated acute neurobehavioral side effects of corticosteroid therapy in preschool versus school‐age children by obtaining structured reports weekly for 1 month.ProcedureParents of 62 children (2–17 years) treated on Dana‐Farber Cancer Institute (DFCI) ALL Consortium Protocol 00‐01 participated during the continuation phase of treatment. Patients received cyclical twice‐daily 5‐day courses of prednisone (PRED; 40 mg/m2/day) or dexamethasone (DEX; 6 mg/m2/day). Parents completed behavior rating scales about their child weekly during one steroid cycle [baseline (Day 0), active steroid (Day 7), post‐steroid (Days 14 and 21)].ResultsBehavioral side effects increased significantly (P < 0.001) during the steroid week for preschool children (<6 years) on measures of emotional control, mood, behavior regulation, and executive functions, returning to baseline during the two “off‐steroid” weeks. In contrast, school‐age children (≥6 years) did not demonstrate an increase in side effects during the steroid week. Steroid type (PRED vs. DEX) was not a significant predictor of neurobehavioral side effects.ConclusionsPreschool children are at greater risk for neurobehavioral side effects during active steroid treatment for ALL than school‐age children and adolescents. DEX was not associated with more neurobehavioral side effects than PRED. Counseling of families about side‐effects should be adapted according to age. The observed effects, moreover, were transient, reducing concerns about longer‐term neurobehavioral toxicities. Pediatr Blood Cancer 2011; 57: 492–498. © 2011 Wiley‐Liss, Inc.