IN PATIENTS WITH BCR-ABL-POSITIVE ALL IN CR PERIPHERAL-BLOOD CONTAINSLESS RESIDUAL DISEASE THAN BONE-MARROW - IMPLICATIONS FOR AUTOLOGOUS BMT

Residual leukemic cells are detectable at frequencies as low as 1 in 1 0(6) normal cells in patients with Philadelphia chromosome/BCR-ABL-pos itive leukemias in complete remission (CR) using reverse-transcriptase polymerase chain reaction (RT-PCR) with specific nested primers. The level of minimal residual disease (MRD) in the bone marrow (BM) and th e peripheral blood (PB) may favor one of the two as the source for an autologous graft. In order to quantify MRD with RT-PCR we analyzed pat ients ficolled cells after limiting logarithmic dilutions in normal fi colled buffy-coat cells. In six patients with BCR-ABL-pos ALL who were in CR by conventional criteria (5 in CR1 and 1 in CR2), we studied a total of nine paired BM and PB samples prior to scheduled ABMT. A posi tive RT-PCR signals was detectable in all samples up to dilutions rang ing from 1:10(1) to 1:10(3) in PB, and at higher titers ranging from 1 :10(3) to 1:10(5) in the BM. The BM titers exceeded the corresponding PB titers in all nine sample pairs by at least 1 log. The mean differe nce was 1.55 log (geometric mean, n = 9) and is statistically signific ant (p < 0.03). We conclude that residual leukemia in BCR-ABL-positive ALL preferentially locates in the BM compartment, and we assume that PB may yield autologous grafts with significantly less leukemic contam ination.