Favorable Impact of the t(9;11) in Childhood Acute Myeloid Leukemia

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Abstract
PURPOSE: To determine the impact of MLL rearrangements on the outcome of children with acute myeloid leukemia (AML). PATIENTS AND METHODS: We analyzed the clinical and biologic features of 298 infants and children with primary AML treated on four consecutive institutional clinical trials. The Kaplan-Meier method was used in survival analysis and the Cox proportional-hazards model was used to analyze the effect of potential prognostic factors on event-free survival (± 1 SE). RESULTS: Molecular studies of 152 cases detected 42 with MLL rearrangements. The karyotypes of these 42 revealed the t(9;11) (15 cases), abnormalities of chromosomes 10 and 11 (nine cases), the t(11;19) (four cases), other abnormalities of 11q23 (seven cases), and miscellaneous rearrangements (seven cases). Among these 42 patients, the 15 whose leukemic cells carried the t(9;11) had a better outcome (66% ± 15%) than the other 27 (25.9% ± 11.2%; P = .004). Cases with the t(9;11) were also characterized by M5 AML morphology (21 of 23 cases). Of the 63 patients with M5 AML, the 21 whose leukemic cells demonstrated the t(9;11) had a better outcome (71.1% ± 11%) than the other 42 (25.8% ± 7.9%; P = .0004). The only independent factors indicating a favorable prognosis were presenting leukocyte count less than 50 × 10 9 /L (relative risk of relapse, 0.73; 95% confidence interval, 0.55 to 0.97; P = .03) and the t(9;11) (relative risk of relapse, 0.32; 95% confidence interval, 0.16 to 0.64; P = .002). CONCLUSION: We conclude that the t(9;11) is the most favorable genetic factor for patients with AML treated at our institution.

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