MOLECULAR STUDIES OF CHIMERISM AND MINIMAL RESIDUAL DISEASE AFTER ALLOGENEIC PERIPHERAL-BLOOD PROGENITOR-CELL OR BONE-MARROW TRANSPLANTATION

We investigated 23 patients for their chimerism status who underwent a llogeneic transplantation using peripheral blood progenitor cells (PBP CT) for chronic myelogenous leukemia (CML) (n = 14), acute myelogenous leukemia (AML) (n = 5), acute lymphoblastic leukemia (n = 1), myelody splasia (MDS) (n = 1), and Hodgkin's disease (HD) (n = 2), These data were compared with those of patients after allogeneic BMT after matchi ng them for disease and disease stage, sex of donor and recipient, GVH D prophylaxis, conditioning therapy and degree of HLA disparity, Patie nts were studied monthly up to 16 months post-transplant. In 11 of 23 (48%) patients who were transplanted with PBPCs and in 18 of 23 (78%) patients after BMT a mixed chimerism was detected at 1 month post-tran splant. After 3 months, six of 21 (29%) evaluable patients after PBPCT remained mixed chimeric as opposed to 12 of 21 (57%) patients after B MT, We also assessed minimal residual disease using detection of the c himeric BCR/ABL transcripts by PCR of CML patients in this study, In f our of 14 (29%) patients who underwent PBPCT, the BCR/ABL chimeric tra nscript was detected, while after BMT eight of 14 (57%) CML patients r emained BCR/ABL positive, In two of these BMT patients, a cytogenetic relapse developed subsequently, and one other patient suffered a hemat ological relapse, whereas one of the CML patients relapsed after PBPCT , The present data may indicate that after PBPCT the incidence of leuk emic relapse is similar or even lower than after BMT.