Bone marrow transplantation has been used to increase the long-term survival 
for patients with acute leukemia and holds the major hope for cure in patients 
who relapse (5-12). For patients undergoing an HLA-matched sibling 
allogeneic bone marrow transplant (AlloBMT), the long-term survival is 
approximately 50% for AML transplanted in first remission (10). 
Unfortunately, only 30% of patients with acute leukemia have a HLA- 
matched donor (9-13). 
In patients who survive alloBMT and do not relapse, there is a significant risk 
of chronic graft-versus-host disease (GVHD). The success of AlloBMT is 
related to the patients age; pediatric patients have a better outcome in most 
series, and most centers now exclude patients over 50 years old (7,9,10). 
2.2 Autologous Bone Marrow Transplantation 
Autologous bone marrow transplantation (ABMT) is increasingly used to treat 
malignant disease (14-32). 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 availability 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, ABMT may allow the generation of endogenous activated killer cells 
with antineoplastic function that help eliminate residual leukemia cells (21). 
ABMT for acute leukemia is becoming an increasingly common procedure. 
Preliminary data for ABMT in acute leukemia are encouraging (13,14,17- 
22,25,28). The 3 year disease-free survival is approximately 30 to 40% for 
AML patients transplanted in first remission (17,27). The relapse rate is 
higher for ABMT than AlloBMT, 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 (11,27). 
2.2.1 Use of Busulfan/Cytoxan followed by ABMT 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 the autologous marrow to graft and establish normal 
hematopoiesis rapidly. The combination of busulfan and cytoxan is 
highly effective as a preparative regimen for AlloBMT in AML and 
has acceptable defined toxicities (17,24). This combination apparently 
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