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Aim. To study the pattern of complex chromosome damages (CCD) in acute leukemias (AL) and their place in the development of post-transplant recurrences (PTR) of AL. Materials and methods. Cytogenetic and partially molecular biological studies of bone marrow cells were conducted in 10 patients with PTR. Of them, 6 patients were diagnosed as having acute lymphoblastic leukemia (ALL), including T-ALL and Ph-positive ALL in 2 and 4 patients, respectively; and 4 patients had acute non-lymphoblastic leukemia (ANLL), including one case secondarily induced by previous polychemotherapy (PCT) and irradiation. The standard G-band staining technique complemented by multicolor fluorescence in situ hybridization in one of the cases was used. Results. It was shown that CCD had the similar pattern in 4 patients before transplantation and in PTR, progressed in 4 more patients, was absent or unnoticed in the early stage of the disease. The other recurrent chromosomal abnormalities that are worthy of notice are as follows: a) the presence of two Ph chromosomes in the cells of two of the 4 patients with Ph+ ALL; b) the frequent involvement of chromosome pairs 9, 19, 5, and 7 into the numerical and structural rearrangements. Conclusion. The important feature of PTR of AL is cellular CCDs, a portion of which is clearly related to previous PCT and may be of pathogenetic value for the development of recurrences.

Overall survival and relapse rates in 62 patients after allogeneic hemopoietic stem cells transplantation according to posttransplantation chimerism values are presented. Significant differences in 5-year overall survival rate have been found in patients with complete donor and mixed chimerism on days 30 and 100 after transplantation with myeloablative conditioning regimens. The influence of chimerism in different time point after transplantation for relapse rate is shown.