A PALG Prospective Multicenter Clinical Trial to Compare the Efficacy of Two Standard Induction Therapies (DA-90 vs DAC) and Two Standard Salvage Regimens (FLAG-IDA vs CLAG-M) in AML Patients ≤ 60 Years Old

The successful treatment of acute myeloid leukemia (AML) depends on the ability to achieve complete remission (CR) and to prevent relapse. Both may be affected by the efficacy of induction chemotherapy. The gold standard for treatment since 1982 has been DA, a regimen of three days of daunorubicin (DNR) and seven days of cytarabine (Ara-C) which results in complete remission in 50 to 75% of patients; this is typically administered intravenously, with daunorubicin administered at a dose of 45 mg per square meter of body-surface area daily for three days, and cytarabine given at a dose of 100 mg per square meter daily for seven days. Neither substituting DNR with another anthracycline nor the addition of thioguanine or etoposide has been demonstrated to improve outcome. Recently it has been proved that high-dose daunorubicin (90 mg/m2) in induction (DA-90) resulted in a higher rate of complete remission (70.6% vs. 57.3%, P<0.001) and improved overall survival (median, 23.7 vs. 15.7 months; P = 0.003) without any increase in serious adverse events, compared with the standard dose of the drug.

An alternative method to intensify induction treatment is by the addition of the purine analog cladribine. Cladribine was demonstrated to increase cellular uptake of Ara-C and accumulation of Ara-CTP in leukemic blasts by 50% to 65% and to have direct antileukemic activity based on incorporation of metabolites into the DNA of proliferating cells. In two randomized trials by the Polish Adult Leukemia Group (PALG), the investigators demonstrated that the combination of cladribine with DNR (60 mg/m2) and Ara-C (DAC) resulted in a significantly increased CR rate after a single induction course compared with the standard two-drug induction (DA-60). The DAC arm was found to have a survival advantage over the DA-60 arm for patients aged 50 years or older (P =. 005), those with an initial leukocyte count above 50G /L (P < .03), and those with an unfavorable karyotype (P < .03). Both induction protocols have the same level of recommendation by the National Cancer Comprehensive Network (NCCN) for routine use (level I), and are commonly used for the treatment of newly diagnosed AML in Poland.

As no randomized comparison of these two standard protocols has yet been performed, the aim of the proposed study is to compare the efficacy of these two standard induction protocols in terms of achievement of CR, early leukemia elimination (at day seven, post induction) and quality of remission measured by minimal residual disease level. Additionally, overall survival (OS), event-free survival (EFS) and disease-free survival (DFS) will be analyzed. It is also intended to compare the hematological and non-hematological toxicity of both regimens.

However, in younger adults with AML treated with standard induction chemotherapy, 20-35% do not achieve CR and 50-70% with CR may be expected to relapse within three years. Patients with primary refractory disease and with relapses following CR1 have a significantly poorer outcome. The optimum strategy at the time of relapse or for patients with refractory disease remains uncertain. Allogeneic transplantation can be curative for the minority of patients who achieve second CR (2CR) and for whom a suitable donor is available. For the majority of patients, additional chemotherapy is given in the hope of achieving remission. Most salvage therapies utilize high or intermediate doses of arabinoside cytosine (Ara-C) in combination with other agents to overcome resistance in leukemic cells. Previous studies have shown that a combination of the purine analog fludarabine (FA) and cytosine arabinoside (Ara-C) increases the accumulation of Ara-C-5' triphosphate (Ara-CTP) responsible for the cytotoxic effect in leukemic blasts. This combination of FA plus Ara-C was initially explored in refractory and relapsed AML patients with satisfactory results. It is also likely that these results can be improved by the addition of granulocyte-colony stimulating factor (G-CSF). Such a combination of FA, Ara-C, idarubicin and G-CSF (the FLAG-IDA regimen) has been used in the treatment of refractory and relapsed AML and poor prognosis myelodysplastic syndromes (MDS), with CR rates of between 30-80% being reported. Recent studies have shown that another purine analog, cladribine (2-CdA), is also able to enhance Ara-CTP accumulation in leukemic blasts and that the combination of 2-Cda with Ara-C exhibited synergistic effect on inhibition of myeloid leukemic cell proliferation, induction of apoptosis, and on disruption of mitochondrial membrane potential.

Two previous PALG studies have confirmed that the CLAG-M regimen (a combination of cladribine, Ara-C, G-CSF and mitoxantrone) has high efficacy and low toxicity in refractory/relapsed AML patients. This salvage regimen was particularly effective in a very poor-risk subgroup with primary refractoriness, early relapse or relapse after stem cell transplantation. Both salvage protocols, CLAG-M and FLAG-Ida, are wildly used in the treatment of relapsed/refractory AML and both have the highest level of NCCN recommendation. However, these two standard salvage protocols have yet to be examined as part of any randomized study. Therefore, the aim of this study is to compare the efficacy of these two standard reinduction protocols (CLAG-M vs FLAG-IDA) in terms of achievement of CR, and quality of remission measured by minimal residual disease level. Additionally, the overall survival (OS), event-free survival (EFS) and disease-free survival (DFS) will be analyzed. The study will also compare the hematological and non-hematological toxicity of both regimens.

The study will include newly-diagnosed AML patients, not suffering acute promyelocytic leukemia; aged 18-60 years, who are eligible for standard induction chemotherapy. The patients will be randomized to one standard induction regimen (DAC or DA-90). At day seven after completion of induction, a bone marrow aspiration with MRD will be performed for an early evaluation of response to treatment. Patients without bone marrow blast reduction below 10% at day seven after induction will be given a second early induction course. Patients who do not achieve CR after two induction courses will be randomized to one of the standard salvage regimens (FLAG-IDA or CLAG-M). Postremission treatment intensity will be adjusted to risk group based on cytogenetic and molecular risk factors at diagnosis and AML biology (secondary AML, therapy related AML). Patients with a low risk of relapse will be allocated to consolidation, with three courses of high doses of Ara-C (HiDAC), or two courses of HiDAC with subsequent autologous stem cell transplantation. Intermediate- or high-risk patients will be referred for allogeneic stem cell transplantation, if they have a matched donor. Until transplantation, consolidation with HiDAC will be continued.

The primary end point of the study is CR rate after one and two induction courses. The secondary end-points are the quality of CR (MRD), OS, DFS, PFS, CR rate after salvage regimen.

It is planned to include 582 patients with newly-diagnosed AML. This will allow a 10% difference in CR rate between DAC and DA-90 induction regimens to be confirmed with a power of 80% and level of significance 0.05.

The study includes neither any experimental drug nor procedures that are not of the standard of treatment for AML.