Predicting relapse of chronic myelogenous leukemia after allogeneic bone marrow transplantation by bcr-abl mRNA and DNA fingerprinting.

Fourteen patients treated by allogeneic bone marrow transplantation for chronic myelogenous leukemia (CML) were evaluated by the polymerase chain reaction (PCR) for bcr-abl-specific transcripts. Nine patients were transplanted in the first chronic phase, three in the second chronic phase, and two in the accelerated phase. All patients achieved a complete cytogenetic and hematologic remission after bone marrow transplantation. Twelve patients are alive (median, 18 months; range, 5-54 months) and two patients died early. bcr-abl mRNA was persistently detectable for 6 to 54 months in four patients (patients 1, 3, 4, 6). From two of them, DNA fingerprint analysis showed only donor type DNA although bcr-abl mRNA was detectable. bcr-abl mRNA was never detectable posttransplant in three patients (patients 2, 5, 13). Six patients had detectable bcr-abl mRNA (patients 8-12, 14): by 6 months, all of these patients were bcr-abl mRNA negative. One patient (patient 7) had detectable full bcr-abl mRNA again at 12 months, but was then negative at 20 months. Ten patients (patients 2, 4-8, 10-13) had never detectable Philadelphia (Ph1) chromosome t(9.22) translocation, whereas four patients had detectable Ph1 (patient 1, 3, 9, 14); by 6 months, three of four cases were negative. One patient (patient 1) had detectable Ph1 at 44 months, but was negative at 50 months. Three of six patients who initially had bcr-abl mRNA detectable posttransplant (patient 7-9) became negative for bcr-abl mRNA at the time of development of chronic graft-versus-host disease (GVHD). These results suggest that the detection of subclinical Ph1 positive cells by PCR is not associated with imminent clinical or cytogenetic relapse. Moreover, graft-versus-leukemia (GVL) activity may contribute to the treatment of minimal residual disease in CML after allogeneic bone marrow transplantation.