Clinical Outcome in Patients with AML Exhibiting Poor Mobilization of Progenitor Cells.

Intensification of post-remission therapy in patients with AML increases the rate of long-term remissions. High-dose chemotherapy and/or radiotherapy followed by autologous stem cell transplantation have therefore been shown to be promising strategy in the management of AML. The aim of this study was to assess the clinical outcome and risk of relapse in patients with low mobilizing capacity.

Materials and methods: Patients from 3 Haematology Departments in Poland were treated according to 3+7 or 3+7+Cladribine protocols. Progenitor cell collection was conducted usually following the 2^nd consolidation cycle. Mobilization was conducted in 238 patients in CR. PB was a main source of progenitor cells. The potential influence of recognized prognostic factors (age, WBC, cytogenetics), the number of chemotherapy cycles conducted prior to achieving CR, time elapsed from CR to mobilization, duration of aplasia following chemotherapy (<21 days) and the number of CD34+cells in mobilized material (0, <1, 1–2×10⁶/kg CD34+), on the mobilization capacity, the clinical outcome and the risk of a relapse, was assessed.

Results: AutoHSCT was conducted in 199 patients. In 39 cases it was not possible to obtain an adequate number of cells for transplantation (<2×10⁶/kg CD34+) (16,4%). Within that group, maintenance therapy was conducted in 17 (43,6%), auto+alloHSCT was conducted in 19 cases (48,7%), alloHSCT was conducted in 3 cases (7,7%). A relapse occurred in 20 patients (51,3%). Initial WBC, age, CD34+ immunophenotype, morphological subtype, number of induction cycles, duration of cytopenia and the treatment method following ineffective mobilization (mainenance therapy vs. autoSCT, vs. alloSCT) have been shown to have no influence on mobilization capacity and the risk of relapse. Cytogenetics was obtained only in 35% of the cases for the reason that the influence of this factor on the mobilization and the risk of relapse had not been assessed. None of the following parameters; ie. number of MNC, CD34+, CFU-GM, BFU-E cells affected the risk of relapse. However it is likely, having compared a group of patients who did not undergo transplantation with a group of patients who underwent transplantation, that the low number of CD34+ cells is a factor that does not negatively affect the duration of CR.

Conclusions: AutoHSCT results obtained are comparable to those achieved in other centres (3ys LFS of 50%). We have found a high percentage of “poor mobilizers”. None of the examined prognostic factors proved to be beneficial in the assessment of the risk of ineffective mobilization of progenitor cells. The lack or poor mobilization of progenitor cells has not been shown to be a negative prognostic factor in patients with AML, as regards clinical outcome and risk of relapse. New prognostic factors, that would allow the isolation of a group of patients with AML, for whom autoHSCT would be the therapy of choice, should be investigated.