prior therapy. In the 5-FU treated group vs. control, median 
recovery times for platelet count to 50,000/mm3 were 20 days 
and 30 days respectively (p=0.01) and for platelet count to 
100,000/mm3 were 23 days and 30 days respectively (p=0.007). 
Neutrophil recovery was not significantly changed. Thus, 
5-FU treatment of patients prior to marrow harvest results 
in enrichment of multifactor responsive HPP-CFC and possibly 
provides superior platelet recovery. 
In addition, 5-FU has been used in murine systems and 
primate models to enhance retroviral transduction of 
progenitor cells as discussed later. Patients in this 
protocol are treated with 5-FU prior to marrow harvest in 
order to 1) possibly enhance marrow recovery post-transplant 
and 2) continue to evaluate the transduction efficiency of 
pre and post-FU marrow samples in vitro. The data presented 
above reassures us that 5-FU treatment of patients in vivo 
is safe and possibly improves marrow recovery post- 
transplant. 
Autologous Marrow Transplantation in CML : 
Ph- cells may be found in the peripheral blood or bone 
marrow of patients with CML after intensive chemotherapy, 
after interferon therapy, or after grgwth _of bone marrow 
progenitors in long-term culture. - it is possible 
that these cells include benign, viable stem cells capable 
of repopulating the bone marrow compartment after intensive 
therapy and autologous stem cell transplantation. Most 
patients have been harvested in chronic phase of the disease 
and, with the onset of acceleration or transformation, 
autotransplantation is performed in an attempt to 
re-establish chronic phase disease. Reiffers and co-workers 
reported the results of ABMT in 45 patients with CML in 
accelerated (11 patients) or blast crisis (35 patients) . 
Most patients recurred with disease within a median time of 
28 weeks. Five patients had transient suppression of the 
Philadelphia chromosome and only 3 patients remained in 
chronic phase at 17, 23 and 54 months. “ s Whether failure to 
control disease with autotransplantation was a result of a 
reinfusion of leukemia cells with the autograft or a 
recurrence of leukemia from cells which survived the 
intensive conditioning regimen is unknown. 
Animal and preclinical human studies attest to the 
value of eradicating tumor cells from marrow prior to 
transplant. In humans a number of phase I/II studies 
utilizing in vitro chemotherapy or long term culture 
techniques have attempted to purge leukemia cells from the 
autograft in order to improve survival and potentially cure 
patients with CML. Barnett and co-workers reported on 10 
patients with CML harvested in first chronic phase (6 
patients) , in accelerated phase or in 2nd or 3rd chronic 
phase (4 patients) treated with intensive therapy ana 
Recombinant DNA Research, Volume 16 
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