Objective Monitoring of minimal residual disease (MRD) and cellular chimerism in patients with hematopoietic malignancies after allogeneic hematopoietic stem cell transplantation(allo-HSCT).

Methods From May 2001 to June 2005, seventy four patients were received allo-HSCT. Including 50 Males and 24 females. 41 patients received sibling HLA-matched BMT, 7 patients received un-related BMT, 9 patients received Nonmyeloablative stem cell transplantation (NST), 14 patients received related haploidentical transplantation and 3 patients received allo-PBSCT. Among them, 45 patients were diagnosed with CML, 13 patients with AML, 14 patients with ALL, one patient with Multiple myeloma and one patient with malignant lymphoma. Chimerism and MRD were monitored using X and Y specific centromeric probes or gene probes for BCR/ABL, MLL and AML1/ETO by fluorescence in situ hybridization (FISH),1000 cells were analysised.

Results Among 18 patients, received sex-matched transplant, we did not found the former chromosome rearrangements in 14 patients after transplantation, MRD were detected in 17% and 10% of cells in two patients, MRD were decreased from 10% to 1% of cells after the reduction of the dose of immunotherapy in one patient four month later, the patient was still in remission one year after transplantation. Another patient died of sever GVHD after the reduction of immunotherapy. 2 patients were found to have the former chromosomal rearrangement 1 and 4 month after transplantation respectively who did not achieve remission after chemotherapy and died 3 and 5 months respectively after transplantation. Over 99% donor chimerisms were found in 44 patients on day 25, donor cells were at a low level (96.2%~98.7) in 7 patients on day 25, and increased over 99% on day 180, they were in remission without relapse. The donor chimerisms decreased gradually in 6 patients, host cells were found over 20 cells, 3 patients showed cytogenetic or hematologic bone marrow relapse, two patients died of sever GVHD after the reduction of cyclosporine A, Over 99% donor chimerisms was achieved in one patient. Conclusion FISH could play a pivotal role in the detection of MRD and chimerism. It is helpful to the evaluation of graft and relapse, to the guide of implement of early immunotherapy.

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