Routine use of microarray-based gene expression profiling to identify patients with low cytogenetic risk acute myeloid leukemia: accurate results can be obtained even with suboptimal samples

Specific signatures were first defined so that all 71 acute promyelocytic leukemia, leukemia with t(8;21) or inv(16)-AML as well as cytogenetically normal acute myeloid leukemia samples with at least 60% blasts and good quality control criteria were correctly classified (training set). The classifiers were then evaluated for their ability to assign to the expected class 111 samples considered as suboptimal because of a low leukemic blast load (n = 101) and/or poor quality control criteria (n = 10) (test set).With 10-marker classifiers, all training set samples as well as 97 of the 101 test samples with a low blast load, and all 10 samples with poor quality control criteria were correctly classified. Regarding test set samples, the overall error rate of the class prediction was below 4 percent, even though the leukemic blast load was as low as 2%. Sensitivity, specificity, negative and positive predictive values of the class assignments ranged from 91% to 100%. Of note, for acute promyelocytic leukemia and leukemias with t(8;21) or inv(16), the confidence level of the class assignment was influenced by the leukemic blast load.Gene expression profiling and a supervised method requiring 10-marker classifiers enable the identification of favorable cytogenetic risk acute myeloid leukemia even when samples contain low leukemic blast loads or display poor quality control criterion.Prognostic evaluation is a critical step in newly diagnosed patients with acute myeloid leukemia (AML) in order to identify those at high risk of relapse. For AML patients, cytogenetic abnormalities as well as gene mutations and/or hyper-expressions detected at diagnosis are the main prognostic factors guiding the initial treatment strategy in a risk-oriented manner [1-4]. Hypergranular acute promyelocytic leukemia (APL), as well as AMLs with either translocation t(8;21)(q22;q22) [t(8;21)-AMLs] or inversion inv(16)(p13q22)/t(16;16)(p13;q22) [inv(16)-AMLs], are well-defined entities associated wit