Adult Acute Myeloid Leukemia in Remission
Allogeneic bone marrow transplantation (BMT) results in the lowest incidence of leukemic relapse, even when compared with BMT from an identical twin (syngeneic BMT). This has led to the concept of an immunologic graft-versus-leukemia effect, similar to (and related to) graft-versus-host disease. The improvement in freedom from relapse using allogeneic BMT as the primary postremission therapy is offset, at least in part, by the increased morbidity and mortality caused by graft-versus-host disease, veno-occlusive disease of the liver, and interstitial pneumonitis. The DFS rates using allogeneic transplantation in first complete remission have ranged from 45% to 60%.[11,12,13] The use of allogeneic BMT as primary postremission therapy is limited by the need for a human leukocyte antigen (HLA)-matched sibling donor and the increased mortality from allogeneic BMT of patients who are older than 50 years. The mortality from allogeneic BMT that uses an HLA-matched sibling donor ranges from 20% to 40%, depending on the series. The use of matched, unrelated donors for allogeneic BMT is being evaluated at many centers but has a very substantial rate of treatment-related mortality, with DFS rates less than 35%. Retrospective analysis of data from the International Bone Marrow Transplant Registry suggests that postremission chemotherapy does not lead to an improvement in DFS or OS for patients in first remission undergoing allogeneic BMT from an HLA-identical sibling.[Level of evidence: 3iiiA]
A common clinical trial design used to evaluate the benefit of allogeneic transplant as consolidation therapy for AML in first remission is the so-called donor-no donor comparison. In this design, newly diagnosed AML patients who achieve a complete remission (CR1), have one or more siblings, and are deemed medically eligible for allogeneic transplant undergo HLA typing. If a sibling donor is identified, the patient is allocated to the transplantation arm. Analysis of outcome is by intention to treat; that is, patients assigned to the donor arm who do not receive a transplant are grouped in the analysis with the patients who did actually receive a transplant. Relapse-free survival (RFS) is the usual endpoint for this type of trial. Overall survival (OS) from the time of diagnosis is less frequently reported in these trials. Results of these trials have been mixed, with some trials showing a clear benefit across all cytogenetic subgroups, and others showing no benefit.
Investigators attempted to address this issue with a meta-analysis using data from 18 separate prospective trials of AML patients using the donor-no donor design, with data from an additional six trials included for sensitivity analysis. The trials included in this meta-analysis enrolled adult patients aged 60 and younger during the years 1982 to 2006. Median follow-up ranged from 42 months to 142 months. Preparative regimens were similar among the different trials. Allogeneic transplant was compared to autologous transplant (6 trials) or to a variety of consolidation chemotherapy regimens with high-dose cytarabine being the most common.