Polymerase chain reaction for detection of residual leukaemia.

The occasional finding of cells positive for the Philadelphia (Ph) chromosome months or years after bone-marrow transplantation for chronic myeloid leukaemia raises the possibility that the Ph-positive clone may never be eradicated. The polymerase chain reaction with probes able to detect the transcript of the bcr/abl hybrid gene at very low levels was used to study marrow cells from seven patients in continuing haematological and cytogenetic remission 5-7 years after allogeneic bone-marrow transplantation for chronic myeloid leukaemia. No evidence of the leukaemic mRNA was found. Thus, it seems that all leukaemic cells were eradicated in these patients and that they are truly cured.