Limited efficacy of a four-day course of high-dose cytosine arabinoside in the treatment of poor-risk patients with acute nonlymphocytic leukemia.

High-dose cytosine arabinoside therapy was administered to 29 patients with poor-prognosis acute nonlymphocytic leukemia. In an attempt to reduce toxicity, therapy was divided into an initial 4-day course of therapy, followed by a 3-day course of the marrow aspirate examined 1 week after the end of treatment contained substantial numbers of leukemic cells. Of the 29 patients, 5 entered complete remission, 2 of them after the initial 4-day course of therapy. The toxicity of split-course therapy was the same as that of conventional 6-day high-dose cytosine arabinoside therapy. This study demonstrates that the modification of high-dose cytosine arabinoside therapy used in this study failed to reduce toxicity and produced a lower remission rate than that obtained with the 6-day course of therapy.