MINIMAL RESIDUAL DISEASE IN BONE-MARROW TRANSPLANT RECIPIENTS WITH CHRONIC MYELOID-LEUKEMIA

Bone marrow samples of 70 transplant recipients with CML were studied by Southern blot analysis and RT-PCR using a two-step procedure with n ested primers. Twenty-two patients were studied once and 48 were asses sed on multiple occasions. All patients remained in a hematological re mission during the study. The time of follow-up after the transplant r anged from 2 to 144 months with a median of 42 months. Thirty-nine pat ients (56%) were negative by RT-PCR and Southern blot studies at the t ime of their last evaluation. The proportion of RT-PCR negative patien ts increased with the duration of follow-up after the transplant; 36% of patients were RT-PCR negative after 1 year compared with 60% after 2 years and 78% after greater than or equal to 5 years. Patients maint ained on immunosuppression had a higher probability of remaining RT-PC R positive. Age, sex, time from diagnosis to BMT, as well as acute and chronic GVHD did not influence the RT-PCR status. The majority of pat ients studied on multiple occasions demonstrated a stable RT-PCR and S outhern blot pattern. Some showed uni- or multi-directional transition s. However, none of the patients studied progressed to a hematological relapse. RT-PCR studies on colonies grown from RT-PCR positive, South ern blot negative patients confirmed that some of the clonogenic proge nitors are able to produce BCR/ABL transcripts.