The effect of body mass index (BMI) on the treatment outcomes of children with acute myeloid leukemia (AML) is unclear and needs further evaluation.

Children with AML (n = 314) who were enrolled in 4 consecutive St. Jude protocols were grouped according to BMI (underweight, <5th percentile; healthy weight, 5th to 85th percentile; and overweight/obese, ≥85th percentile).

Twenty‐five patients (8%) were underweight, 86 patients (27.4%) were overweight/obese, and 203 patients (64.6%) had healthy weight. The 5‐year overall survival rate of overweight/obese patients (46.5% ± 7.3%) was lower than the rate of patients with healthy weight (67.1% ± 4.3%; P < .001); underweight patients also tended to have lower survival rates (50.6% ± 10.7%; P = .18). In a multivariable analysis that was adjusted for age, leukocyte count, French‐American‐British classification, and study protocols, patients with healthy weight had the best survival rate among the 3 groups (P = .01). When BMI was considered as continuous variable, patients with lower or higher BMI percentiles had worse survival (P = .03). There was no difference in the occurrence of induction failure or relapse among BMI groups, although underweight and overweight/obese patients had a significantly higher cumulative incidence of treatment‐related mortality, especially because of infection (P = .009).

An unhealthy BMI was associated with worse survival and more treatment‐related mortality in children with AML. Meticulous supportive care with nutritional support and education, infection prophylaxis, and detailed laboratory and physical examination is required for these patients. These measures, together with pharmacokinetics‐guided chemotherapy dosing, may improve outcome. Cancer 2012. © 2012 American Cancer Society.