Comparison of the Peripheral Blood Stem Cell Mobilization and Harvest after Each Consolidation Chemotherapy in Patients with Acute Myeloid Leukemia in First Complete Remission Who Underwent Autologous Stem Cell Transplantation.

Background: Peripheral blood stem cells (PBSC) are increasingly being used to restore hematopoiesis following high-dose chemotherapy in patients with acute myeloid leukemia (AML) without an HLA-matched related donor. However, which of consolidation-mobilization chemotherapy cycles are the most compatible in terms of the yield of progenitor cells and outcomes after autologous peripheral blood stem cell transplantation (APBSCT) has not been known.

Patients and methods: 49 mobilization procedures performed on 28 patients with AML who underwent APBSCT enrolled at three centers. The treatment protocols administered to patients with AML consisted of an induction chemotherapy in combination with cytarabine or BHAC plus idarubicin, and consolidation chemotherapy with high dose cytarabine (3 g/m² iv bid, day 1, 3 and 5). In all patients, the collection of PBSC was performed during recovery after giving consolidation chemotherapy and granulocyte colony-stimulating factor (G-CSF).

Results: 28 AML patients in first complete remission (CR) underwent total 49 aphereses to obtain a minimum dose of 2×10⁶/kg CD34+ cells/kg after each consolidation chemotherapy. First, second and third consolidation cycles were 17, 24 and 8, respectively. According to the total collected CD34+ cells ×10⁶/kg, two main groups were considered that is, poor mobilizers (PM), with a collection of < 2×10⁶/kg, and good mobilizers (GM), with a collection of ≥ 2×10⁶/kg. Of 49 consolidation cycles, 15/17 (88.23%), 16/24 (66.66%) and 3/8 (37.5%) were GM after 1st, 2nd and 3rd consolidation cycles, respectively (P=0.012). The median follow up was 22 months (range 3–59). PBSC mobilization after first plus second versus third consolidation chemotherapy that was used for APBSCT were compared. The 2-year disease-free survival (DFS) rate was 36.1% and 64.3% (P=0.161), and the 2-year overall survival (OS) rate was 34.9% and 80% (P=0.190). Patients who were infused with ≥ 2 ×10⁶/kg CD34+ cells at APBSCT had a shorter DFS rate at 2 years, 25.0%, than those with < 2 ×10⁶/kg CD34+ cells, 53.8%. However, there were no significant differences between the two groups (P=0.169). Relapse rate after stem cells infusion which mobilized from first, first plus second, second and third consolidation cycles were 60% (3/5), 61.1% (11/18), 50% (4/8) and 2/6 (33.3%), respectively.

Conclusion: If reinfused CD34+ cells are adequate, the stem cells harvested after third consolidation chemotherapy may be the best source for APBSCT in view of relapse rate and DFS.