Low‐dose cytosine arabinoside (Ara‐C) therapy in the myelodysplastic syndromes and acute leukemia

Twenty‐two patients with either a myelodysplastic syndrome or acute nonlymphocytic leukemia were treated with 10–21 days of subcutaneous cytosine arabinoside (Ara‐C) (5–10 mg/m² every 12 hours). There were two complete remissions and ten partial responses. Clinically significant improvements in peripheral blood counts persisted for periods of 8 weeks to greater than 21 weeks. Responses were seen even in patients who had previously proven refractory to conventional induction regimens or high‐dose Ara‐C. The toxicity, however, was considerable. Nearly all patients developed significant thrombocytopenia. Platelet and red cell transfusion support was required in many cases. The response to low‐dose Ara‐C therapy seen in patients with the leukemic and myelodysplastic disorders may be mediated by the induction of cell differentiation or a direct cytotoxic effect on a sensitive population of cells. Low‐dose Ara‐C may provide an alternative therapy in the selected patient with acute nonlymphocytic leukemia or a myelodysplastic syndrome.