Inv (11)(p15q21) in donor-derived Ph-negative cells in a patient with chronic myeloid leukemia in relapse successfully treated with imatinib mesylate post allogeneic stem cell transplantation

Cytogenetic studies in acute leukemia patients relapsing after allogeneic stem cell transplantation

We analyzed karyotype stability in 22 patients with acute leukemia at relapse or disease progression after allogeneic stem cell transplantation (allo-SCT). Karyotypes before and at relapse after allo-SCT were different in 15 patients (68%), the most frequent type being clonal evolution either alone or combined with clonal devolution (13 patients). Patients with and without a karyotype change did not differ significantly in overall survival (OS) (median, 399 vs. 452 days; P = 0.889) and survival after relapse (median, 120 vs. 370 days; P = 0.923). However, acquisition of additional structural chromosome 1 abnormalities at relapse after allo-SCT occurred more frequently than expected and was associated with reduced OS (median, 125 vs. 478 days; P = 0.008) and shorter survival after relapse (median, 37 vs. 370 days; P = 0.002). We identified a previously undescribed clonal evolution involving t(15;17) without PML-RARA rearrangement in an AML patient. We conclude that a karyotype change is common at relapse after allo-SCT in acute leukemia patients. Moreover, our data suggest that additional structural chromosome 1 abnormalities are overrepresented at relapse after allo-SCT in these patients and, in contrast to a karyotype change per se, are associated with reduced OS and shorter survival after relapse.

Long-term persistence of nonpathogenic clonal chromosome abnormalities in donor hematopoietic cells after allogeneic stem cell transplantation

We describe the cases of two unrelated patients who exhibited multiple chromosomal abnormalities in donor cells after allogeneic peripheral blood stem cell transplantation (PBSCT). The patients were diagnosed with chronic myeloid leukemia and chronic lymphocytic leukemia, respectively, and both underwent nonmyeloablative conditioning with cyclophosphamide and fludarabine followed by PBSCT from their HLA-matched opposite-sex siblings. Post-transplant bone marrow cytogenetics showed full engraftment, and the early post-transplant studies demonstrated only normal donor metaphases. Subsequent studies of both patients, however, revealed a population of metaphase cells with abnormal, but apparently balanced, donor karyotypes. Chromosome studies performed on peripheral blood cells collected from both donors after transplantation were normal. Both patients remained in clinical remission during follow-up of approximately 8 years in one case, and 6 years in the other case, despite the persistence of the abnormal clones. Chromosomal abnormalities in residual recipient cells after bone marrow or PBSCT are not unusual. In contrast, only rare reports of chromosome abnormalities in donor cells exist, all of which have been associated with post-bone marrow transplant myelodysplastic syndrome or acute leukemias. The present cases demonstrate the rare phenomenon of persistent clonal nonpathogenic chromosome aberrations in cells of donor origin.