The prognostic significance of early response to treatment has not been reported in relapsed pediatric acute myeloid leukemia. In order to identify an early and easily applicable prognostic factor allowing subsequent treatment modifications, we assessed leukemic blast counts in the bone marrow by morphology on days 15 and 28 after first reinduction in 338 patients of the international Relapsed-AML2001/01 trial. Both day 15 and day 28 status was classified as good (≤20% leukemic blasts) in 77% of patients. The correlation between day 15 and 28 blast percentages was significant, but not strong (Spearman correlation coefficient = 0.49, P<0.001). Survival probability decreased in a stepwise fashion along with rising blast counts at day 28. Patients with bone marrow blast counts at this time-point of ≤5%, 6-10%, 11-20% and >20% had 4-year probabilities of survival of 52%±3% versus 36%±10% versus 21%±9% versus 14%±4%, respectively, P<0.0001; this trend was not seen for day 15 results. Multivariate analysis showed that early treatment response at day 28 had the strongest prognostic significance, superseding even time to relapse (< or ≥12 months). In conclusion, an early response to treatment, measured on day 28, is a strong and independent prognostic factor potentially useful for treatment stratification in pediatric relapsed acute myeloid leukemia. This study was registered with ISRCTN code: 94206677.

• MeSH
• Leukemia, Myeloid, Acute diagnosis   drug therapy   mortality   pathology   MeSH
• Survival Analysis MeSH
• Bone Marrow Cells drug effects   pathology   MeSH
• Daunorubicin therapeutic use   MeSH
• Child MeSH
• Remission Induction MeSH
• Humans MeSH
• Adolescent MeSH
• Drug Monitoring MeSH
• Child, Preschool MeSH
• Prognosis MeSH
• Antibiotics, Antineoplastic therapeutic use   MeSH
• Antineoplastic Combined Chemotherapy Protocols MeSH
• Recurrence MeSH
• Check Tag
• Child MeSH
• Humans MeSH
• Adolescent MeSH
• Male MeSH
• Child, Preschool MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Multicenter Study MeSH
• Randomized Controlled Trial MeSH