Chromosomal translocation t(6;9) (p23;q34) associates with acute myeloid leukemia (AML), although that is found in less than 2% of all cytogenetic events in children with AML. Recent molecular analysis of patients with t(6;9) (p23;q34) has demonstrated a rearrangement of the genes DEK and CAN resulting in the formation of a chimeric DEK-CAN mRNA. The prognosis of patients with t(6;9) is thought tobe very poor, because of poor response to chemotherapy and/or high relapse rate. However, recent reports showed that allogeneic hematopoietic stem cell transplantation may have a potential to improve the prognosis of patients with t(6;9). We report here we were able to monitor DEK-CAN fusion transcripts in the serial points along chemotherapy courses and hematopoietic stem cell transplantation in a child with t(6;9). A 5-yaer-old Japanese boy diagnosed as having AML (M5b). Chromosomal analysis revealed t(6;9)(p23:q34), and real-time quantitative polymerase chain reaction (RQ-PCR) revealed positive chimeric DEK-CAN mRNA. After diagnosis, he received an induction chemotherapy. At the end of the induction chemotherapy, he was in a hematological and cytogenetic complete remission (CR), however DEK-CAN fusion transcript was still positive. After completion of five courses of consolidation therapy, he was in hematological and cytogenetic CR, although molecular minimal residual disease (MRD) was still positive. So he received allogeneic peripheral blood stem cell (PBSC) transplantation from 1 locus mismatched father. Busulfan and Melpharan were used for conditioning regimen. Cyclosoprin A and short course of methotrexate were emplyed for the prophylaxis of graft-versus-host disease (GVHD). Engraftment of PBSC was achieved at day 15. He had mild acute GVHD and no clonic GVHD. Bone marrow analysis at the time of engraftment revealed hematological, cytogenetic, and molecular CR. Now he is still in a persistent molecular negativity of DEK-CAN fusion transcript by RQ-PCR and keeps event-free survival for five years after PBSCT. The monitoring of DEK-CAN fusion transcript in the chemotherapies was reported from some investigators. However, there were very few reports about the monitoring DEK-CAN fusion transcripts before and after hematopoietic stem cell transplantations. In coclusion, we succeeded to exclude DEK-CAN fusioin transcript after hematopoietic stem cell transplantation in a child with t(6;9) AML. We conclude that DEK-CAN molecular monitoring by RQ-PCR in is a useful tool for the management of patients with t(6;9) AML.

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