Rearrangement of the Myeloid/Lymphoid Leukemia Gene in Therapy-Related Myelodysplastic Syndrome in Patients Previously Treated with Agents Targeting DNA Topoisomerase II

Background: Therapy-related acute myeloid leukemias (t-AML), with balanced translocations affecting the 11q23 point in the myeloid/lymphoid leukemia (MLL) gene, are one of the most serious complications of treatments with topoisomerase II inhibitors. However, only a few reports of t-AML exist. We aimed to study if these translocations are cumulative-dose-dependent, their frequency in therapy-related myelodysplastic syndrome and the relationship between their presence, the type of therapy and the response criteria. Methods: This retrospective study included 120 patients with various malignancies (108 non-Hodgkin’s lymphoma, 8 Hodgkin’s disease and 4 neuroblastoma) in remission, being treated with topoisomerase 2 inhibitors; 74 had been diagnosed with therapy-related myelodysplasia and 46 did not have dysplasia. All bone marrow biopsy samples were evaluated by fluorescence in situ hybridization for 11q23 point breakage in the MLL gene. Results: MLL gene rearrangement frequency was 6% in dysplastic versus 2% in nondysplastic groups; p < 0.001. It was associated with a worse overall survival (mean 13 ± 2 vs. 39 ± 3 months, log-rank p value