Hematopoietic Stem Cell Transplantation in Acute Promyelocytic Leukemia in the Era of All-Trans Retinoic Acid (ATRA) and Arsenic Trioxide (ATO)

SIMPLE SUMMARY: Acute promyelocytic leukemia (APL) currently benefits from first-line treatment based on all-trans retinoic acid and arsenic trioxide, ensuring long-term complete responses for most patients. However, a proportion of 5–20% of patients relapse, and their long-term survival, even in the context of therapy with the mentioned drugs, is no longer as favorable, requiring the association of a highly efficient consolidation. Current recommendations indicate hematopoietic stem cell transplantation as consolidation treatment in patients with relapsed APL who achieve a new complete remission. Our article aims to present the current data on the role of transplantation in APL and the aspects regarding this therapy that are still under debate, as well as new data on possible alternatives to this type of treatment. ABSTRACT: Acute promyelocytic leukemia (APL) currently represents one of the malignant hemopathies with the best therapeutic responses, following the introduction of all-trans retinoic acid (ATRA) and subsequently of arsenic trioxide (ATO) treatment. As a result, a large proportion of patients with APL achieve long-term responses after first-line therapy, so performing a hematopoietic stem cell transplant as consolidation of first complete remission (CR) is no longer necessary. Even in the case of relapses, most patients obtain a new remission as a result of therapy with ATO and ATRA, but an effective consolidation treatment is necessary to maintain it. The experience accumulated from studies published in the last two decades shows the effectiveness of hematopoietic stem cell transplantation (HSCT) in improving the outcome of patients who achieve a new CR. Thus, the expert groups recommend transplantation as consolidation therapy in patients with a second CR, with the indication for autologous HSCT in cases with molecular CR and for allogeneic HSCT in patients with the persistence of minimal residual disease (MRD) or with early relapse. However, there is a variety of controversial aspects related to the role of HSCT in APL, ranging from the fact that outcome data are obtained almost exclusively from retrospective studies and historical analyses to questions related to the type of transplantation, the impact of minimal residual disease, conditioning regimens, or the role of other therapeutic options. All these questions justify the need for controlled prospective studies in the following years.