Phase I/II Clinical Study of Idarubicin Dose Intensification for Remission Induction Therapy in Acute Myeloid Leukemia Patients Age of 65 Years or Less

Up to nowadays, a standard induction therapy for acute myeloid leukemia(AML) has consisted of cytarabine 100-200 mg per square meter of body surface area(BSA) per day continuous infusion for 7 days with idarubicin 12 mg per square meter or daunorubicin 45 mg per square meter of BSA per day for 3 days. This standard therapy induces a complete remission(CR) in 50-75% of young adults and 40-50% of older adults. Recently two cooperative groups prospectively compared 45 mg per square meter of daunorubicin to 90 mg per square meter of BSA. They reported high-dose daunorubicin, as compared with a standard dose one, resulted in a significantly higher CR rate and improved overall survival(OS) up to age 65 without additional toxic effects.

Daunorubicin has been more commonly used anthracycline; however, idarubicin has a longer intracellular retention time and has shown more rapid clearance of marrow blasts. In the early 1990, three prospectively randomized studies showed that a combined regimen of idarubicin and cytarabine was superior to one of daunorubicin and cytarabine for the induction therapy of AML in adults. When they compared daunorubicin 45-50 mg per square meter with idarubicin 12-13 mg per square meter for induction therapy, there were no significant differences in hematologic and non-hematologic toxicities, including cardiac toxicity.

Phase I studies of idarubicin in patients with acute leukemia and chronic myelogenous leukemia in blast crisis reported the dose-limiting toxicities(DLT) were stomatitis and anorexia at the maximum tolerated dose(MTD) of 15 mg per square meter of BSA per day for 3 days. Based on the results of these studies, the investigators have generally administered idarubicin 12 mg per square meter per day for 3 days for the remission induction therapy of AML. Meanwhile Sanz et al. had administered idarubicin 12 mg per square meter per day for 4 days in patients with acute promyelocytic leukemia, and Tedeschi et al. had done a single high-dose idarubicin 40 mg per square meter combined with high-dose cytarabine 3 g per square meter per day for 5 days in patients with acute lymphoblastic leukemia, with no significant increase of severe toxicity. The MTD of idarubicin should be reevaluated in the treatment of acute leukemia, especially in the era of granulocyte colony-stimulating factor and better supportive care available.

In this phase I study, idarubicin 12 mg per square meter of BSA per day for 3 days will be given to three patients at the first stage and then the idarubicin dose will be increased by 3 mg per square meter of BSA each stage. The phase I study consists of 3 stages and the idarubicin dose will be increased up to 18 mg per square meter of BSA per day for 3 days unless DLTs do not develop in more than 33% of enrolled patients at each stage. In the subsequent phase II study, the MTD being determined from the phase I study or 18 mg per square meter of idarubicin will be given to the enrolled patients. There were three large studies which enrolled a total of 942 previously untreated adult patients with AML and in which idarubicin 12-13 mg per square meter of BSA per day for 3 days and cytarabine 100 mg per square meter daily for 7 days were administered intravenously. Therefore, the investigators can adopt them as historical control groups in terms of statistical assessment.

In conclusion, the investigators desire to determine the safety and effectiveness of the intensified dose of idarubicin in the treatment of acute myeloid leukemia through this phase I and II study.