Addition of Cladribine to the Standard AML Treatment Improves Long-Term Outcome in High Tumor Burden and Older Than 40 Years Acute Myeloid Leukemia Patients. Five-Year Follow-Up of the Polish Adult Leukemia Group (PALG 1999 DAC vs. DA Study).

The goal of the study was to evaluate long-term outcome of acute myeloid leukemia (AML) patients treated within the PALG 1999 DAC vs, DA Study.

Between 1999–2002, 445 patients, aged 18–60 years, were randomized to the induction DAC-7: daunorubicin 60 mg/m²/d iv 1–3; cytarabine 200 mg/m²/d ci 1–7; cladribine 5 mg/m² 2h inf. iv d 1–5 or standard DA-7 regimen (the same regimen without cladribine). Patients achieving CR received two courses of subsequent intensive consolidation: 1) HAM (HD AraC, mitoxantrone) 2) HD AraC with or without cladribine in the DAC-7 or DA-7 arm, respectively. In case of PR after the first induction course the same regimen was repeated, NR patients received CLAG (2-CDA, HD-AraC, G-CSF), regardless the randomization arm. Post-consolidation therapy was in both arms comparable.

As previously reported, a single course of DAC-7 induction resulted in 17% higher CR rate compared to the DA-7 treatment. The difference was particularly pronounced in a population of patients >40 years and for those with initial WBC >100x10⁹/L. In the latter subgroup also the overall CR rate (achieved after >=1 induction course) was higher in the DAC-7 arm (71% vs. 43%). [Leukemia. 2004 May;18(5):989–97]

In the present report we analyzed long-term outcome (median follow-up 3.2 years) in the whole study group and in pre-defined subgroups taking into account initial tumor burden, age, cytogenetics, FAB subtype, and preceding myelodysplasia. At five years the overall survival (OS) rate equaled 31% for DAC-7 and 25% for DA-7 arm (p=0.42) and leukemia free survivall (LFS) 32% vs. 29% (p=0.38), respectively.

The subgroup analysis revealed higher probability of the OS in patients with initial WBC ≥100 G/l assigned to DAC-7 compared to DA-7 arm (39% vs. 11%, p=0.02). The LFS rate and the probability of relapse equaled 50% and 32% (p=NS) and 36% and 68% (p=0.0497), respectively.

In patients aged >40 years, the therapy containing cladribine was associated with improved LFS (30% for DAC-7 vs. 20% for DA-7, p=0.01), and a tendency to improved OS (28% vs. 18%, p=0.09). In this subgroup DAC-7 therapy resulted in reduced relapse incidence (60% vs. 69%, p=0.04).We conclude that addition of cladribine to induction/consolidation therapy of AML may improve long-term outcome in higher age ranges patients and in those with high tumor burden. The improvement results mainly from reduced risk of relapse, and, in patients with high initial WBC, from higher CR rate.