Outcome of Allogeneic Hematopoietic Stem-Cell Transplantation for Acute Myeloid Leukemia (AML) with 11q23 (MLL) Rearrangement (MLL-r AML). A Retrospective Analysis From the Acute Leukemia Working Party of EBMT

Abstract 498

Acute myeloid leukemia (AML) with 11q23 (MLL) rearrangement (MLL-r AML) belongs to the intermediate or high risk cytogenetic classification. It prognosis is known to depend on the translocation partner. Data from multicenter studies suggest that most patients with t(11q23) achieve complete remission after induction chemotherapy. However, the impact of different t(11q23) on long-term outcome is less clear, with overall survival (OS) rates at 5 years ranging from 0% to 45%. A more favourable outcome has been reported in patients receiving an alloHSCT in an early phase. To investigate the potential role of alloHSCT for the management of t(11q23) AML we analyzed the outcome of the cases reported to the ALWP between 2000 and 2010 (median year of transplant: 2007). Overall, we identified 172 patients (median age: 41, 18–70; 43% male) allografted. The following rearrangements were identified: t(9;11) in 82 patients, t(11;19) in 20, t(6;11) in 21, t(10;11) in 17, t(4;11) in 5, t(11;17) in 5 and others in 22. Most transplants were performed in complete response (CR1=148, 86%; CR2=21, 12%, CR3=3, 2%). Donor was an HLA-identical sibling in 84 transplants (49%), and an unrelated in 88 (51%). Conditioning regimen consisted of a myeloablative regimen in most patients (n=113, 65%), and source of stem-cells was peripheral blood in 110 (64%), bone marrow in 49 (28%), and cord blood in 13 (8%). One hundred sixty-six patients engrafted and 57 presented an acute GVHD ≥ 2. After a median follow-up of 24 months (2–123), 2-year overall survival (OS) was 56 ± 4%, 2-year leukemia-free survival (LFS) was 52 ± 4%, CI of relapse incidence (RI) was 35±3%, non-relapse mortality (NRM) was 16±4% and the rate of chronic GVHD was 47±4%. The outcome was significantly different (p<10⁻⁴) according to the rearrangement with a 2-year LFS for patients with t(9;11) of 61±6%, t(11;19) of 65±11%, t(6;11) of 12±10%, t(10;11) of 34±12%. LFS was improved by CR status with a 2-y LFS for CR1 patients of 56 ± 5% and only 23 ± 9% for patients in more advanced disease. We subsequently restricted our analysis on the population of 148 patients in first CR in which the 2-year LFS was for patients with t(9;11) of 64±6%, t(11;19) of 68±12%, t(6;11) of 16±10%, t(10;11) of 40±13%, the 2-year RI was for patients with t(9;11) of 23±5%, t(11;19) of 26±11%, t(6;11) of 55±15%, t(10;11) of 36±14%, the 2-year NRM was for patients with t(9;11) of 24±13%, t(11;19) of 6±5%, t(6;11) of 29±13%, t(10;11) of 24±13%. Multivariate analysis on LFS identified as poor prognostic factors: the presence of a t(6;11)(p<0.0001) or t(10,11) (p = 0.034) and an interval from diagnosis to CR1 greater than 43 days (p=0.008). This preliminary study confirms the known good prognosis of t(9;11) and poor outcome of t(6;11), while it highlights the good prognosis of t(11;19) AML patients submitted to alloHSCT in CR1, suggesting that this procedure might overcome the adverse prognosis associated to this entity.