No Significant Difference in Therapy Results between Acute Myeloid Leukemia Patients with Myeloblastic Bone Marrow Infiltration within the Range of 20–29% and over 29% at Diagnosis.

Definition of acute myeloid leukemia (AML) includes a heterogenous group of disorders differing in cytogenetics, clinical symptoms and prognosis. A common feature is bone marrow infiltration with leukemic clone which is also present in peripheral blood and different organs.

Over thirty years ago the FAB (French-American-British) group defined the morpho-cytochemical classification of acute leukemias and proposed ≥30% leukemic blasts in bone marrow for a threshold between muelodysplastic syndromes and acute leukemias. In 2002 the WHO group of experts decided to decrease this border line to 20%.

The question concerning differences in results of particular treatment programs for AML patient subgroups with original blastic bone marrow infiltration within the range of 20–29% and ≥30% remains disputable.

To address this question we performed an analysis in 405 patients treated according to the PALG (Polish Adult Leukemia Group) protocol DAC and DA. At diagnosis there were 26 patients with myeloblastic bone marrow infiltration ranging 20–29% (group A) and 379 patients with infiltration ≥30% (group B). In 62,5% patients (n=10) of the group A AML was preceding by myelodysplastic syndrome.

In the time period 1999–2002 patients under study received as induction DAC-7 regimen: 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.

Complete remission (CR) rate was comparable in both populations and reached 73% in the group A and 70% in group B. There were also no statistical differences between overall survival (OS) and leukemia free survival (LFS) between both groups. OS after 5 years equals 34% in group A and 27% in droup B and LFS 42% and 27%, respectively (p=NS).

Our study proves that there are no differences in treatment results between AML patients with original bone marrow infiltration within 20–29% and ≥30% given the same treatment. It confirms that the revised WHO criteria are reasonable.