Reduced intensity conditioning prior to allogeneic stem cell transplantation for patients with acute myeloblastic leukemia as a first-line treatment.

BACKGROUND: Thirty-three patients (median age 52; range 26-60) with acute myeloblastic leukemia (AML) were included in a pilot study of allogeneic stem cell transplantation (Allo-SCT) following a reduced-intensity conditioning (RIC).

METHODS: Patients achieving first complete remission (CR1) were selected for their high-risk clinical and/or leukemic features. All patients received two courses of consolidation chemotherapy including one high-dose cytarabine course. Among them, 13 patients in addition received a high-dose melphalan course followed by autologous SCT. Then, all patients received an RIC Allo-SCT combining fludarabine, busulfan, and antithymocyte globulin.

RESULTS: All patients engrafted had cumulative incidences of Gluksberg System Grade 2 acute and chronic graft-versus-host-disease (GVHD) of 24 (9-39%) and 64 (48-80%), respectively. Three patients died from nonrelapse causes (NRD) (cumulative incidence: 9%, 95% confidence interval (CI): 0-19) and 6 relapsed (cumulative incidence: 18%, 95% CI: 5-31). With a median follow-up of 18 months (range 7-52) after Allo-SCT, 26 patients are alive, of whom 24 remained in CR1 for a 2-year overall survival and leukemia-free survival (LFS) probabilities of 79 (range 61-90%) and 76 (range 59-87%), respectively. In a 'landmark' analysis starting on Day 100, the occurrence of chronic GVHD was associated with a lower relapse rate (0% vs. 44%: P = 0.007) and improved outcome (LFS; 95% vs. 53%, P = 0.007; overall survival, 95% vs. 61%, P = 0.05).

CONCLUSIONS: We conclude that the sequential combination of intensive chemotherapy and allogeneic immunotherapy might offer relatively low NRD and leukemia relapse rates even in high-risk patients.