A Risk-Oriented Therapeutic Strategy for Adult Acute Myelogenous Leukemia

Adult AML is a difficult-to-treat illness because of both biological and therapeutic reasons.

As to the first point, many patients are aged >50 years and/or present with significant comorbidity and/or AML-related risk features (poor risk cytogenetics, prior myelodysplasia, secondary AML).

As to the second point, standard-type remission induction therapy is ineffective in 20% or more of the patients, whereas the application of the more effective postremission consolidation options (alloSCT, high-dose cytarabine courses) is often flawed by high-grade toxicity which can offset expected benefits, particularly in older age groups (>50-55 years), where therapy-related death rates are seen in 5%-10% of the cases (chemotherapy) or more (transplants).

Against this background an explorative study was developed in which:

• All patients aged 16-65 years were considered eligible (acute promyelocytic leukemia excluded), including those with an antecedent diagnosis of myelodysplasia/hematological disorder and/or secondary AML. Both age and disease subtype selection criteria are broader than in most studies on adult AML, adhering more closely to the reported epidemiology of the disease.
• Remission induction was attempted with a two-step regimen, consisting of conventional chemotherapy (ICE: idarubicin/cytarabine/etoposide +G-CSF) followed, only in the case of failure to respond, by a sequential high dose-cytarabine cycle (cytarabine 3 g/m2/bd on days 1,2,8,9; idarubicin on days 3 and 10; G-GSF; cytarabine dosing 2 g/m2 in patients aged >55 years). It was hoped that this choice would optimize salvage rates (hence overall response rates), by allowing more patients (and more fit, uncomplicated ones) to reach the salvage phase, compared to a policy where salvage is usually given after two failed induction courses.
• Remission consolidation was risk-oriented, the risk being defined through a mixed clinico-cytogenetic model. Thus all patients entering CR after one/two cycles were stratified as HR or SR according to what is reported below. Once defined the risk class, therapy consisted of an alloSCT for HR patients, and of 3 consecutive monthly cytarabine-based cycles (2 g/m2/bd on days 1-5; idarubicin on days 1,2) in SR patients, each cycle being followed by the reinfusion of a limited amount of autologous blood stem cells (1-2x10e6/kg CD34+ cells) and G-CSF. Blood stem cells were collected following an early consolidation cycle with intermediate-dose cytarabine plus G-CSF. HR patients unable/unfit to proceed to alloSCT were offered instead the SR-type multicycle cytarabine consolidation, whereas all patients unable to mobilize autologous stem cells were treated with one/two intermediate-dose cytarabine course(s).

HR: high-risk cytogenetics or intermediate-risk/normal cytogenetics with FLT3 mutation and/or any one or more additional clinical risk factor(s), i.e. total WBC >50x10e9/l, FAB subtype M0, M6 or M7, prior myelodysplasia or secondary AML,hepatosplenomegaly, late CR (cycle 2), or favorable cytogenetics with late CR (cycle 2).

SR: favorable cytogenetics (without associated high-risk abnormalities and in CR after cycle 1) or intermediate-risk/normal cytogenetics without FLT3 mutation and/or without any one additional clinical risk factor(s), i.e. total WBC >50x10e9/l, FAB subtype M0, M6 or M7, prior myelodysplasia or secondary AML,hepatosplenomegaly, late CR (cycle 2).

Inclusion criteria

• age 15-65 years,untreated AML (de novo, secondary, myelodysplasia-related, granulocytic sarcoma),untreated high-risk myelodysplasia (RAEB, RAEB-T), informed consent

Exclusion criteria

• acute promyelocytic leukemia, comorbidity precluding intensive chemotherapy approaches