Study of the time course of mixed chimerism by fluorescent in situ hybridization in patients with chronic myeloid leukemia after allogenic transplantation of bone marrow

AIM: To determine the type of chimerism in patients with chronic myeloid leukemia (CML) in various periods after allogenic transplantation of bone marrow (TBM) and its association with subsequent relapse. MATERIALS AND METHODS: Ten patients were examined after allogenic TBM, which was performed during the chronic phase of CML in 9 patients and during acceleration phase in 1. Two patients received therapy with donor lymphocytes during relapse after transplantation. Time course of chimerism and minimum residual illness was studied by standard cytogenetic methods, fluorescent in situ hybridization (FISH) with DNA probes to centromer sites of X and Y chromosomes and BCR and ABL genes. The studies were carried out 30, 60, 90, 180 days, 9 months, 1 year, and then every 6 months after transplantation. RESULTS: Mixed chimerism was observed in all patients during 9 months after TBM. The count of host cells was 0.1-5.8% in 8 patients; later the count of autologous cells was less than 1% in 5 patients, and in 3 patients complete donor chimerism was observed. Clinical hematological remission was stable in these patients. Relapses of leukemia with 40 and 83.1% host cells occurred in 2 patients 13 and 23 months after transplantation, respectively. Donor lymphocytes were transfused in order to induce the graft versus host effect, and in patient No. 2 restoration of donor hemopoiesis was attained. CONCLUSION: Highly sensitive FISH method with DNA probe to centromer sites of X and Y chromosomes detects early relapse of the disease and demonstrates the time course of donor hemopoiesis recovery after transfusion of donor lymphocytes. The data indicate that 9 months after transplantation molecular cytogenetic studies should be carried out more often (once a month), particularly in patients with poor prognosis, for earlier detection of the relapse and beginning of immunotherapy.