Low-dose Cytarabine for Acute Myeloid Leukaemia and Myelodysplastic Syndromes: in Vivo and in Vitro Cytotoxicity

14 patients with acute myeloid leukaemia (AML) and 7 with myelodysplastic syndrome (MDS) were treated with cytarabine in low dosage. In AML a complete remission rate of 43% was found and in all patients profound cytopenia was noticed without any sign of maturation induction. In MDS no effect of low-dose cytarabine could be detected. We also studied the effect of low-dose cytarabine in vitro in freshly isolated leukaemic cells of 10 patients with AML. Maturation induction was measured by a comprehensive panel of quantitative and qualitative markers of maturation. No differentiation inducing effect of low-dose cytarabine could be found. We conclude on the basis of our own results and after reviewing the literature that low-dose cytarabine exerts its effect by cytotoxicity instead of maturation induction.