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Acute myeloid leukemia, Refractory anaemia with excess of blasts in transformation, World Health Organization classification
Patients with ? 20% <30% bone marrow blast infiltration previously regarded as a transitional category between myelodisplasia and acute myeloid leukemia (AML) according to FAB classification, have been subsequently included into AML WHO classification. However, controversies still remain as to whether the natural history and responsiveness to therapy of these patients is comparable to that of patients with > 30% BM blast AML. In the present review, we will discuss the clinical results achieved in the treatment of elderly patients with 20%-30% BM blasts AML using intensive chemotherapy (IC) or hypomethylating agents. Overall, due to concerns of treatment-related morbidity and mortality associated with delivery of IC, approximately only 30% of all patients ? 65 years are considered eligible for this approach. Therefore, a great deal of attention has been dedicated to hypomethilating agents such as azacitidine and decitabine. These agents have shown efficacy, with reduced toxicity as compared with IC, when administered to elderly patients not eligible for IC and with 20-30% BM blasts and multilineage dysplasia. Future randomized clinical trials are eagerly awaited to determine whether hypomethylating agents can substitute for IC even in elderly patients with good functional status.