DETECTION OF BCR ABL TRANSCRIPTS BY RT-PCR AND THEIR COLORIMETRIC EVALUATION IN CHRONIC MYELOID-LEUKEMIA PATIENTS RECEIVING ALLOGENEIC BONE-MARROW TRANSPLANTATION/

Background. Chronic myeloid leukemia (CML) is a disease characterized by the presence of a unique molecular marker, i.e. the fusion gene bcr -abl and its mRNA and protein products. This marker permits minimal re sidual disease follow-up after bone marrow transplantation (BMT) throu gh cytogenetic or molecular analysis. Although the reverse transcripta se polymerase chain reaction (RT-PCR) method is largely employed, the clinical value and impact of a positive RT-PCR as a herald of hematolo gical relapse has not yet been definitively ascertained.Methods. In or der to verify the frequency of bcr-abl positivity in CML patients who underwent alloBMT, we performed serial two-step RT-PCR on 63 periphera l blood and bone marrow specimens obtained at different times after no n T-cell-depleted BMT from 16 CML patients treated in our Institution. After amplification, RT-PCR products were always checked by liquid hy bridization with a specific probe. Median molecular follow-up after BM T was 38 months (range 2-144 months). Results. None of the patients st udied presented clinical hematological relapse after BMT. Six out of s ixteen patients were found to be positive for bcr-abl. PCR positivity appeared in 4/6 patients more than one year post-BMT and in 2/6 patien ts within one year post BMT. In both instances PCR was an isolated fin ding in 5/6 patients and reverted to negativity in subsequent analysis ; only one case was PCR positive twice. It is noteworthy that RT-PCR p ositivity appeared in five patients presenting acute or chronic graft versus host disease (GVHD) and in one patient who had received MUD-BMT . Conclusions. In our cohort of patients, transient bcr-abl positivity had no clinical relevance and was also found in MUD-BMT without heral ding hematological relapse. Our observations further stress the import ance of applying only quantitative PCR methods during the post BMT fol low-up of CML patients.