Prognostic impact of combined fludarabine, treosulfan and mitoxantrone resistance profile in childhood acute myeloid leukemia

Background: The role of cellular drug resistance in childhood acute myeloid leukemia (AML) has not yet been established. The aim of the study was the analysis of the clinical value of ex vivo drug resistance in pediatric AML. Patients and Methods: A cohort of 90 children with de novo AML were assayed for drug resistance profile by the 3-4,5- dimethylthiazol-2-yl-2,5-difenyl tetrazolium bromide (MTT) assay and prognostic model of in vitro drug sensitivity was analyzed. Results: Children who relapsed during follow-up showed higher in vitro resistance of leukemic blasts to most of the drugs tested, except for cytarabine, cladribine, vincristine, mercaptopurine and thioguanine. A combined in vitro drug resistance profile to fludarabine, treosulfan and mitoxantrone (FTM score) was defined and it had an independent prognostic significance for disease free survival in pediatric AML. Conclusion: The combined fludarabine, treosulfan and mitoxantrone resistance profile to possibly may be used for better stratification of children with AML or indicate the necessity for additional therapy.