Kinetics of stem cell engraftment and clearance of leukaemia cells after allogeneic stem cell transplantation with reduced intensity conditioning in chronic myeloid leukaemia.

It is hypothesised that an effective graft-vs.-leukaemia reaction contributes substantially to the therapeutic effect of reduced intensity conditioning stem cell transplantation in chronic myeloid leukaemia. However, kinetic data on eradication of leukaemia cells and stem cell engraftement which could support this assumption are lacking. Thus, we investigated bcr/abl fusion transcripts and haematopoietic chimerism in 14 patients undergoing such a transplantation protocol. Ten of them obtained a complete molecular remission, and two patients achieved haematologic remissions but remained bcr/abl positive. Weekly determinations of bcr/abl transcript numbers by qualitative and quantitative polymerase chain reaction and donor chimerism revealed that 10 responders cleared bcr/abl positive cells from the peripheral blood within a median of 9 wk (range 3-22 wk). The close relation (P = 0.0075) between the first occurrence of graft-vs.-host disease and the complete clearance of bcr/abl positive blood cells argues in favour of an effective graft-vs.-leukaemia reaction.