Minimal residual disease after bone marrow transplant for chronic myeloid leukaemia detected by the polymerase chain reaction.

We describe the methodology and application of the polymerase chain reaction to detect BCR-ABL mRNA as a marker for CML cells. The technique is highly sensitive enabling the routine detection of 1 leukaemic cell in 10(5) or 10(6) normal cells and is therefore the most sensitive method available for detecting minimal residual disease. Analysis of marrow or blood from 80 patients after bone marrow transplantation for CML shows that residual leukemia is often detectable for several months but that most subsequently become PCR negative. Patients who relapsed were all PCR positive before the detection of Philadelphia positive metaphases in bone marrow aspirates.