High-dose cytosine arabinoside, daunomycin and 6-thioguanine in relapsed or refractory acute nonlymphocytic leukemia.

Fifteen patients with relapsed (10) or primarily refractory (5) acute nonlymphocytic leukemia were treated with a combination of cytosine arabinoside (3 g/m2 i.v. every 12 h, 12 doses, days 1-6), 6-thioguanine (100 mg/m2 orally every 12 h, 12 doses, days 1-6) and daunomycin (60 mg/m2 i.v. on days 5 and 6 only). Complete remission was achieved in 11 patients. Eight of 10 relapsed patients and 3 of 5 primarily refractory patients entered remission. Median remission duration was 7.5 months (2-36+ months). Ten of the 11 remissions resulted from a single induction course. The time to hematologic recovery was comparable to that seen with 'standard'-dose cytosine arabinoside regimens. Nonhematologic toxicity, although considerable, was not greater than that seen with high-dose cytosine arabinoside alone. The most significant problem was gastrointestinal toxicity with diarrhea occurring in the majority of patients. Mild neurologic toxicity (reversible cerebellar dysfunction) occurred in 2 patients.