Provided engraftment of normal progenitor cells occurred from both 
aliquots, this outcome would suggest that one of the techniques is 
superior to the other and should be explored further in larger scale 
clinical trials. 
3) Children relapse and the cells are marked with both vectors, but 
progenitor representation of each vector is widely disproportionate and 
there is statistical evidence that one purging technique is more 
effective than the other. 
If no patient relapses with marked cells, then no definitive conclusion 
could be drawn. However, since the initial studies of this technique 
have confirmed the feasibility of marking and detecting residual 
malignant cells in remission marrow this event is unlikely to happen. 
8.0 STATISTICAL CONSIDERATIONS 
8.1 Potential Accrual and Study Duration 
Approximately 25 children newly diagnosed with AML are treated at St. Jude 
each year. The complete remission rate for AML is presently 75% and thus, 
we expect 18 children to be available for bone marrow transplantation (BMT). 
Of these, 30% will have a matched related donor and will be treated with an 
allogenitic BMT. The remaining 12 children are expected to enroll on this 
protocol to be treated with an autologous BMT (ABMT). 
We propose to treat 35 children on protocol with ABMT in order to observe 
14 relapses. Fourteen relapses will provide a reasonable sample size for a 
first statistical evaluation of the two purging techniques. Furthermore, the 
sample size of 75 newly diagnosed AML patients treated with BMT will 
provide at least 80% power for comparison with the historical event-free 
survival results of AML 87. The sample size of 35 children treated with 
ABMT will provide at least 75 % power for comparing duration of CCR to the 
historical AML 87 study. 
8.2 Safety Monitoring 
While there is now considerable experience documenting the toxicity and 
failure rate of ABMT in this setting as well as the safety of the gene marking 
techniques, we will, nonetheless, sequentially monitor the study for an 
unexpected high frequency of these events. A two-staged design will be used 
with 20 patients being treated in the first stage and 15 patients in the second 
stage. Since the primary study objective is the evaluation of purging and not 
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