The Role of Cytogenetic Abnormalities in Acute Myeloid Leukemia with NPM1 mutations and No FLT3 Internal Tandem Duplication.

Nucleophosmin (NPM1) gene mutations are observed in almost one-third of adult acute myeloid leukemia (AML). If the favorable genotype defined by the presence of NPM1 mutations without fms-like tyrosine kinase 3 (FLT3) internal tandem duplication (ITD) is known to be associated with favorable outcome in patients with cytogenetically normal (CN) acute myeloid leukemia (AML), impact of these molecular abnormalities are still debated in those with cytogenetically abnormal (CA) AML.

We analyzed the role of these factors in newly diagnosed AML patients homogeneously treated in the Acute Leukemia French Association (ALFA) trials between 1990 and 2006 (ALFA 9000, 9801, 9802). Among 1529 patients (15-70 years of age), 554 patients were screened for NPM1 mutation, FLT3-ITD and have informative karyotype. Mutations screening were centrally performed according to previously described procedures. Karyotype was considered as normal if at least 20 normal marrow metaphases were present without any abnormal marrow metaphases. Favorable core binding factor (CBF) AML (74 patients) were excluded from this analysis.

Among the 480 remaining patients, 137 (29%; median age 48 years, range 17-68) were NPM1 mutated, 22 of them (16%) having CA-AML. We found no difference between NPM1 mutated CN-AML patients (n=115) and NPM1 mutated non-CBF CA-AML patients (n=22) in term of complete remission rate (88% vs 83%; P= .49), overall survival (OS) (39% vs 38 % at 5 years, P= .85), event-free survival (EFS) (33% vs 25% at 5 years, P= .39). However, in the context of the favorable genotype, EFS was significantly longer in the 79 CN- than in the 16 CA-AML patients (41% vs 19% at 5 years ; P= .04) with a trend to better OS (51% vs 31% at 5 years ; P= .12). No significant differences were observed in patients with NPM1 mutated AML but FLT3-ITD (5-year EFS, 12% vs 40%; 5-year OS, 20% vs 60%; P= .47 and .27, respectively), even if the numbers of patients were here very low (35 CN- vs 5 CA-AML). More importantly, the favorable genotype was predictive of a longer EFS and OS in the 267 patients with CN-AML (5-year EFS, 41% vs 19%; 5-year OS, 51% vs 30%; P= .0001 and .001, respectively), while no differences were observed in the 213 patients with non-CBF CA-AML (5-year EFS, 19% vs 16%; 5-year OS, 31% vs 27%; P= .38 and .36, respectively).

As shown, patients with the favorable genotype but CA-AML had an outcome relatively similar to those with a non favorable genotype and either CA- or CN-AML. The favorable outcome associated with NPM1 mutation in the absence of FLT3-ITD might thus depend on the presence of a normal karyotype. We thus think that larger studies or overviews are needed to definitely answer this question.

Dombret:Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.