Long chemotherapy-free remissions after single-cycle timed-sequential chemotherapy for acute myelocytic leukemia.

Thirty-seven patients with acute myelocytic leukemia were treated with a timed-sequential regimen of arabinosyl cytosine and daunorubicin followed by no further therapy until relapse. The cycle-specific agent arabinosyl cytosine was given by three-day infusion at the time when the malignant cell population was predicted to have a maximal regrowth rate following an initial three-day infusion of arabinosyl cytosine and daunorubicin together. Malignant myeloblasts demonstrated an increased in vivo tritiated thymidine uptake prior to the second infusion. Complete remission was achieved in 56% of previously untreated evaluable patients (65% of all patients less than 60 years of age) with a single cycle of this therapy. Median duration of chemotherapy-free remission for these patients was 10 months, 47% were still in remission at one year and 31% are projected to be in remission at two years. Eight of 11 relapsing patients achieved a second remission with the same regimen and the median survival cannot yet be predicted. These results compare favorably with results from other centers using regimens involving multiple courses of remission induction, consolidation, and continuous maintenance chemotherapy.