7.0 IMPACT OF OUTCOME ON SUBSEQUENT TREATMENT 
7.1 Source and Nature of Relapse |i 
i' 
li 
There would be 2 informative outcomes if the patients relapsed. jl 
li 
1) The majority of relapse patients have no marked cells. However, j 
occasional patients relapse with cells containing the marker gene and j' 
this relapse is monoclonal. This would imply the patients receiving ' 
marrow harvested in remission are in fact receiving occasional ! 
malignant "stem cells" and that relapse is monoclonal in nature. i 
Detection of this event would be of low probability (see Section 8 - * 
below). ' 
2) Most relapses contain both marked cells and unmarked cells and the 
insertion site may be polyclonal. This would imply that marrow 
contains a multiplicity of cells capable of inducing relapse. 
I 
These different outcomes would have different clinical implications. | 
, I 
Outcomes 1 and 2 would imply that purging is indeed a worthwhile procedure ; 
and should be further explored. 
Outcome 2, in which relapse is polyclonal and a high proportion of patients |i 
relapsing therefore show a positive marker, would also provide a unique l| 
method for assessing the effectiveness of different techniques of purging. Such Ij 
methodology is now entirely lacking (see paragraph 1.4). M| 
7.2 Stem Cell Marking ^ I 
-i 
Analysis of the stimuli required in vivo to induce stem cells into cycle, and to ^ | 
induce proliferation of cells of different lineages would greatly simplify efforts |ii | 
to grow adequate marrow in vitro from small aliquots for successful |i| 
subsequent ABMT. Moreover an indication of the cytokines responsible for 5 
stem cell cycling would help in planning more effective chemotherapy and in ( 
optimizing the timing of marrow harvest for subsequent storage and re- T 
infusion. 
h 
i' I 
^*7 
[ 720 ] 
Recombinant DNA Research, Volume 14 
