Kinetics of increasing BCR-ABL transcript numbers in chronic myeloid leukemia patients who relapse after bone marrow transplantation

We prospectively studied 98 chronic myeloid leukemia (CML) patients after bone marrow transplantation by competitive polymerase chain reaction to detect and quantify leukemia-specific BCR-ABL mRNA. Of 69 patients who had persistently undetectable, decreasing, or low BCR-ABL levels ( < 50 transcripts/microgram RNA) on sequential analysis, one (1%) subsequently relapsed. Of 29 patients who had increasing or persistently high BCR-ABL (> 50 transcripts/microgram RNA) on sequential analysis, 21 (72%) have relapsed (P < .00001). In 19 patients studied sequentially, a constant logarithmic increase in the number of BCR-ABL transcripts was found before relapse, indicating a constant BCR-ABL transcript doubling time. The doubling time for patients relapsing cytogenetically or into chronic phase (median, 24.7 days) was significantly longer than that of patients relapsing into advanced phases (median, 14.7 days; P = .005). Eight patients were treated for relapse by donor leukocyte transfusions. The doubling time of responders was significantly longer than that of nonresponders (P = .017). We conclude that quantification of BCR-ABL transcripts after bone marrow transplantation (BMT) is valuable in predicting relapse: a more rapid BCR-ABL transcript doubling time before relapse might indicate a more aggressive disease.