(4) inability of maintenance therapy to eliminate the residual leukemic cell 
burden due to failure of the clonogenic leukemia cells to enter the cell cycle, 
thus precluding cytotoxic effects of S-phase-specific drugs. 
Bone marrow transplantation has been used to increase the long-term survival 
for patients with acute leukemia and holds the only hope for cure in patients 
who relapse. For patients undergoing an HLA-matched sibling allogeneic 
bone marrow transplant (AlloBMT) the long-term survival is approximately 
50% for acute myelogenous leukemia (AML) transplanted in first remission. 
Unfortunately, only 30% of patients with acute leukemia have a HLA-matched 
donor. 
In patients who survive allogeneic BMT and do not relapse, there is a 
significant risk of chronic graft-versus-host disease (GVHD). The success of 
allogeneic BMT is related to the patients age and most centers exclude 
patients over 50, while pediatric patients have a better outcome in most series. 
2.2 Autologous Bone Marrow Transplantation 
Autologous bone marrow transplantation (ABMT) is increasingly used to treat 
malignant disease. The underlying therapeutic concept is that storage of 
marrow harvested in clinical/bone marrow remission allows the patient 
subsequently to be exposed to treatment that would be lethal were it not for 
the avciilability of stored autologous marrow for rescue. The hope is that the 
increased dose of chemotherapy and radiation therapy will cure a higher 
proportion of patients than would be possible with conventional therapy. In 
addition, autologous bone marrow transplantation may allow the generation 
of endogenous activated killer cells with antineoplastic function. 
Autologous BMT for acute leukemia is becoming an increasingly common 
procedure. Preliminary data for autologous BMT in acute leukemia is 
encouraging. The 3 year disease-free survival is approximately 30 to 40% for 
AML patients transplanted in first remission. The relapse rate is higher for 
autologous BMT than allogeneic BMT but the treatment related mortality for 
autologous transplant is less than 10% so that the overall survival for the two 
types of transplant are similar. 
2.2.1 Use of Busulfan/Cytoxan and autologous BMT for AML 
In theory, a preparative treatment for autologous transplantation should 
permit intensification of effective therapies and subsequent rescue of 
hematopoietic function. The ideal regimen for leukemia should have 
anti-leukemic effects which include sanctuary areas, yet should permit 
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