Impact of Cytogenetic and Molecular Markers on Disease-Free Survival of Allogeneic Hematopoietic Stem Cell Transplantation for Acute Myeloid Leukemia

Introduction: Cytogenetics is an independent prognostic factor in acute myeloid leukemia (AML). Molecular genetics including leukemia fusion gene, gene mutation and gene over expression are recognized to have significant impact on survival in patients with AML as well. In present study, the impact of cytogenetic and molecular markers on disease-free survival (DFS) of allogeneic hematopoietic stem cell transplantation (HSCT) for AML was investigated. Methods: Between April 2012 and December 2014, consecutive 345 patients with AML who underwent allogeneic HSCT in our center were analyzed retrospectively. All patients were either in poor-risk or in good-risk/intermediate-risk but with persistent minimal residual disease. The median age was 19 (1.8 to 64) years old. Children (≤14 years) were 96 (27.8%) cases and adults (>14 years) were 249 (72.2%) cases. Male to female was 200:145. The median disease course was 6 (1-64) months. Leukocyte count at diagnosis was < 30 x 10⁹/L in 230 (66.7%) patients (low leukocyte) and ≥30 x 10⁹/L in 115 (33.3%) cases (high leukocyte). Transplants at CR1, ≥CR2, and advanced disease were 168 (48.7%), 53 (15.4%) and 124 (35.9%), respectively. Donor sources were identical sibling (IS) in 45 (13.0%) cases, unrelated (UR) in 71 (20.6%) cases and haploidentical (HI) in 229 (66.4%) cases. Myeloablative conditioning regimens were administered with either Busulfan (Bu) plus Cyclophosphamide (Cy)/Fludarabine (Flu)-based in 285 (82.6%) patients or total body irradiation (TBI) plus Cy/Flu-based in 60 (17.4%) patients. Antithymocyte globulin was used in unrelated and haploidentical HSCT. Unmanipulated bone marrow and peripheral blood stem cells (PBSC) for IS and HI HSCT and PBSC for UR transplant were applied as the grafts. Cyclosporine, short-term Methotrexate, and Mycophenolate mofetil were employed for GVHD prophylaxis. Results: Univariate analysis showed that DFS after allogeneic HSCT in AML was not associated with patient age (children vs. adults, 70.3% vs. 69.4%, p=0.6), leukocyte count at diagnosis (low leukocyte vs. high leukocyte, 68.8% vs. 71.3%, p=0.8), donor source (IS vs. UD vs. HI, 77.3% vs. 76.8% vs. 65.8%, p=0.21), and conditioning regimen (Bu-based vs. TBI-based, 70.1% vs. 67.3%, p=0.45). Multivariate analysis indicated that disease status before HSCT was the only impact factor on DFS (CR1 vs. ≥CR2 vs. advanced disease, 81.6% vs. 70.0% vs. 53.1%, p<0.0001). Therefore, total 221 of 345 patients with AML in complete remission pre-conditioning were analyzed for impact of cytogenetic and molecular markers on survival after HSCT. DFS rates were 79.1%, 80.4%, 74.1% in good-risk, intermediate-risk, poor-risk cytogenetics groups (p=0.81), respectively. According to gene mutations, the DFS rates were 100% in CEBPA+, 91.6% in IDH1+/NPM1+, 85.7% in Flt3-ITD+, 81.5% in c-KIT+, 75.0% in no mutation, 70.2% in MLL-PTD+/ASXL1+/TET2+, 54.3% in Flt3-ITD+ with other mutations (p=0.42). According to gene expression, the DFS rates were 100% in DEK-CAN+, 100% in HOX11+/EVI1+, 84.8% in no abnormal gene expression, 83.3% in CBFb-MYH11+, 78.5% in WT1+, 76.5% in MLL+, 74.9% in AML1-ETO+, 0% in TLS-ERG+ (p=0.004). Conclusions: Under our HSCT protocol, disease status before transplant for the patients with AML has significant impact on DFS but not patient age, leukocyte count at diagnosis, donor source and conditioning regimen. Allogeneic HSCT has attenuated the influence of cytogenetics on DFS in patients with AML. Our preliminary data have shown that patients with CEBPA+, IDH1+/NPM1+, DEK-CAN+, HOX11+/NPM1+ have favorable survival, but patients with both Flt3-ITD+ and other gene mutations or with TLS-ERG+ have poor survival after allogeneic HSCT in AML.