[1511] Acute Myeloid Leukemia with Minimal Differentiation: TdT Expression Is Associated with Better Overall Survival Following Stem Cell Transplantation

Keyur P Patel, Faisal A Khokhar, Tariq Muzzafar, M James You, Farhad Ravandi, Carlos Bueso-Ramos, L Jeffrey Medeiros. The University of Texas M.D. Anderson Cancer Center, Houston, TX

Background: The criteria for the diagnosis of acute myeloid leukemia (AML), not otherwise specified, with minimal differentiation, have been refined in the 2008 World Health Organization (WHO) classification. This neoplasm is also known as M0 using the older, but convenient terminology of the French-American-British classification. TdT expression in AML-M0 is proposed to be a surrogate for RUNX1 mutations, which is reported to be associated with distinct gene expression profiles in AML-M0. In this study, we investigated whether TdT expression has an impact on clinical outcome.
Design: By strictly applying the WHO classification criteria, many previously designated AML-M0 were reclassified, mostly as AML with myelodysplasia-related changes. The study group was further subdivided on the basis of TdT expression. Patient demographics and clinical outcome were obtained from the hospital medical records. Morphologic, immunophenotypic, cytogenetics and molecular testing data were obtained from the laboratory information system. Statistical analysis was performed using Student's two-tailed t-test and Fisher's two-tailed exact test as applicable.
Results: The study group included 30 patients with AML-M0, including 19 men and 11 women with a median age of 60 years (range, 16-87 years). Ten cases of AML-M0 were positive for TdT(+) and 20 cases were negative for TdT(-). Patients with TdT+ AML-M0 had higher peripheral blood and bone marrow blast counts compared to TdT- AML-M0 (p=0.01). Overall survival was significantly longer for the 3 patients with TdT+ AML-M0 compared with the 3 TdT- AML-M0 patients (median: 76.3 months versus 8.9 months, p=0.02). The 3 TdT+ AML-M0 patients who received stem cell transplant had better overall survival compared with 5 TdT+ AML-M0 patients who did not receive stem cell transplant (median: 76.3 months versus 16 months, p=0.007). There was no significant difference in response to induction therapy or achievement of CR between the groups.
Conclusions: We conclude that AML-M0, as currently defined in the 2008 WHO classification, has been substantially refined and yet remains heterogeneous. This category includes at least two groups that can be identified by TdT expression. Although there is a need to assess a greater number of patients, our results suggest that TdT positivity in AML-M0 identifies a subset of patients with a better prognosis after stem cell transplantation.
Category: Hematopathology

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 216, Tuesday Morning


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