Acute myeloid leukemia and reduced-intensity conditioning allogeneic stem cell transplantation: where do we stand?

The development of reduced-intensity conditioning (RIC) for allogeneic stem cell transplantation (SCT) has provided new therapeutic options in severe hematologic malignancies for the older patients, especially in acute myeloid leukemia (AML). Initially developed for the more at-risk patients who cannot benefit from the standard, myeloablative approach because of age or comorbidities, programs are now developed for younger patients. Until now, only open studies and retrospective comparisons between RIC and myeloablative approaches are available. They show that: 1) the RIC approach reduces the transplant-related-mortality (TRM), and especially the early TRM and the early infectious complications. This benefit is not clearly maintained at 1 or 2 years after transplant; 2) the RIC could be associated with a higher risk of leukemia relapse. Finally, there is no clear benefit of the RIC when compared to the classical approach on the disease-free survival. Due to differences in median ages between the classical and RIC cohorts, to different RICs, and different underlying diseases, the practical conclusions of these findings are difficult to draw. However, the RIC approach has been so encouraging in the olders that it is time to develop prospective, eventually randomized studies in order to answer two questions: - What is the place of allogeneic SCT when compared to chemotherapy in AML patients older than 50 or 55 years? - In younger patients who could tolerate both approaches, what is the optimal transplant regimen: RIC or classical? The aim of this paper is to review the actual indications of allogeneic SCT in AML patients, to remind the rational of the RIC approach, to comment the main series of RIC in AML, and to discuss the main issues for the next few years in terms of indication of transplant and choice of the conditioning regimen in these patients.