Prospective Evaluation of Azacitidine Maintenance Following Allogeneic Hematopoietic Stem Cell Transplantation in Patients with High-Risk Acute Myeloid Leukemia and Myelodysplastic Syndrome

Introduction and aim. Relapse following allogeneic hematopoietic stem cell transplantation (HSCT) is a major cause of treatment failure and is associated with a poor prognosis. Overall survivals are around 50% at 5 years following allogeneic HSCT in intermediate and high risk AML. Survivals remain less than 20% in poor-risk and very poor-risk patients based on the cytogenetic profile. Thus, prevention of relapse following allogeneic HSCT remains an unmet clinical need. Low-dose azacitidine maintenance post-HSCT has been shown to augment graft-versus-leukemia effect and may prolong survivals. We aim to prospectively evaluate the effect of azacitidine maintenance following allogeneic HSCT in high risk AML and MDS.

Method. Consecutive patients with high-risk acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) in remission following first allogeneic HSCT or second allogeneic HSCT (from the original donor) were recruited. High risk AML in this study comprised patients with poor risk karyotype, secondary AML transformed from underlying MDS, presence of fms-like tyrosine kinase 3-internal tandem duplication (FLT3 -ITD) and non-remission before HSCT. Azacitidine was administered at 100mg daily for 3 days per cycle every 28 days until progression or a maximum of 8 cycles. The clinicopathologic and treatment characteristics were determined. The occurrence of graft-versus-host disease (GVHD) was determined. DNA chimerism was determined in the bone marrow before the initiation of azacitidine, after 4^th and 8^th cycles of azacitidine and at 1 year. DNA chimerism was determined by quantification of polymorphic short tandem repeat sequences. The progression-free survival (PFS) and overall survival (OS) were determined by Kaplan-Meier analysis.

Results. Thirty-four patients with high-risk AML (N=31) and MDS (N=3) were recruited. The median duration of follow-up was 14 months (range: 2 - 44 months). Twenty-two patients received azacitidine maintenance after first allogeneic HSCT, whereas 12 patients received azacitidine maintenance after a second allogeneic HSCT from the same donor following relapse from a first allogeneic HSCT For patients receiving azacitidine after first HSCT, at a median follow-up of 18.5 months (range: 5- 36 months), the median PFS was not reached, and the median OS was 32 months (95% confidence interval [C.I.]: 24.85-39.15). The 24-month PFS and OS were 66.1% and 73.2% respectively. Acute and chronic GVHD occurred in 7 (31.8%) and 17 patients (77%). For patients receiving azacitidine after second HSCT, at a median follow-up of 14 months (range: 9 - 46 months), the median PFS and OS were 9 months (95% C.I.:6.94-11.04) and 14 months (range: 11.77 - 16.23 months). The 24-month PFS and OS were 25% and 14% respectively. Acute and chronic GVHD occurred in 1 (8.3%) and 5 (41.7%) patients respectively. In both groups, 100% donor chimerism was achieved during azacitidine maintenance.

Conclusion. Azacitidine maintenance following first allogeneic HSCT resulted in favorable 2-year survivals in selected patients with high-risk AML and MDS. Nevertheless, survivals were poor despite azacitidine maintenance after second allogeneic HSCT from the same donor. Full donor chimerism was maintained during azacitidine maintenance.