Allogeneic hematopoietic cell transplantation in patients with AML not achieving remission: potentially curative therapy.

Patients with acute myeloid leukemia (AML) who fail to achieve complete remission (CR) have a dismal prognosis. Although data suggest that durable remissions can be achieved in approximately 30% of patients with refractory or relapsed AML after allogeneic hematopoietic cell transplantation (HCT), only a small fraction of those patients are offered this therapeutic option. Importantly, patients with primary refractory AML have distinctly better outcomes following allogeneic HCT than those with refractory relapse. Access to suitable donors could be one of the main barriers in these situations. However, with recent developments in the field of allogeneic HCT, such as alternative donor sources, high-resolution HLA-typing, reduced intensity conditioning regimens and improvements in supportive care, this approach has the potential to offer long-term survival for patients with refractory and relapsed AML and should be considered as early after diagnosis as possible. Incorporating novel agents into the conditioning regimen or as post-transplant maintenance therapy could further improve outcomes and render older or medically infirm patients with refractory or relapsed AML eligible for allogeneic HCT. In this review, we summarize existing data on allogeneic HCT in patients with refractory or relapsed AML and explore novel approaches with the potential to improve outcomes in this patient population.

Comparison of minimal residual disease as outcome predictor for AML patients in first complete remission undergoing myeloablative or nonmyeloablative allogeneic hematopoietic cell transplantation.

Minimal residual disease (MRD) is associated with adverse outcome in acute myeloid leukemia (AML) after myeloablative (MA) hematopoietic cell transplantation (HCT). We compared this association with that seen after nonmyeloablative (NMA) conditioning in 241 adults receiving NMA (n=86) or MA (n=155) HCT for AML in first remission with pre-HCT bone marrow aspirates assessed by flow cytometry. NMA patients were older and had more comorbidities and secondary leukemias. Three-year relapse estimates were 28% and 57% for MRD(neg) and MRD(pos) NMA patients, and 22% and 63% for MA patients. Three-year overall survival (OS) estimates were 48% and 41% for MRD(neg) and MRD(pos) NMA patients and 76% and 25% for MA patients. This similar OS after NMA conditioning was largely accounted for by higher non-relapse mortality (NRM) in MRD(neg) (30%) compared with MRD(pos) (10%) patients, whereas the reverse was found for MRD(neg) (7%) and MRD(pos) (23%) MA patients. A statistically significant difference between MA and NMA patients in the association of MRD with OS (P<0.001) and NRM (P=0.002) but not relapse (P=0.17) was confirmed. After adjustment, the risk of relapse was 4.51 times (P<0.001) higher for MRD(pos) patients. These data indicate that the negative impact of MRD on relapse risk is similar after NMA and MA conditioning.