Combination of Cladribine and Cytarabine is Effective for Childhood Acute Myeloid Leukemia: Results of the St. Jude AML97 Trial

Because cladribine can increase cytarabine triphosphate levels, we tested a cladribine—cytarabine combination in the St. Jude AML97, trial in which this combination was administered before standard chemotherapy to 96 children with acute myeloid leukemia (AML) or myelodysplastic syndrome. Patients received a 5-day course of cladribine (9 mg/m(2)/dose) and cytarabine either as daily 2-hour infusions (500 mg/m(2)/dose) (arm A) or a continuous infusion (500 mg/m(2)/day) (arm B). Ara-CTP levels and inhibition of DNA synthesis increased from day 1 to day 2, but were not different between the two arms. In addition, the median blast percentages at day 15 did not differ between arms A and B, but patients treated in arm A had shorter intervals between the initiation of the first and second courses of therapy. Thus, although there were trends towards better CR rates and overall survival for patients treated in arm B, the reduced efficacy of arm A may have been partially compensated by more intense timing of therapy for that group. For all patients, 5-yr event-free survival and overall survival estimates were 44.1% ± 5.4 % and 50.0% ± 5.5%. Our results suggest that cladribine in combination with continuous-infusion cytarabine is effective therapy for childhood AML.