Negative impact of FLT3 abnormalities in elderly acute myeloid leukemia patients

Acute myeloid leukemia (AML) of elderly is mostly characterised by karyotypic and molecular changes typically found in secondary AML; it usually expresses inherent disease resistance P-glycoprotein, frequently has an antecedent myelodysplastic syndrome resulting in a poor chemotherapeutic tolerance [1,2]. The majority of cases present cytogenetic aberrations of poor (32–55%) or intermediate (40– 63%) prognostic significance, with only a few patients (5%) harbouring chromosomal changes correlated with a favourable outcome [1,2]. More efforts are thus required to identify additional prognostic parameters capable of distinguishing subjects with lower risk who might benefit from intensive treatment, from those at higher risk who could either be offered palliative and supportive care only or be candidate to non-intensive investigational approaches. In this regard a potentially prognostic genetic marker is represented by FMS-like tyrosine kinase 3 (FLT3) gene, which encodes for a tyrosine kinase receptor and which, in *18–27% and 7–14% of adult AML cases, respectively, harbours an internal tandem duplication (ITD) involving exons 14 and 15, or an activating point mutation, most often D835, in the second tyrosine kinase domain (ATKD). To date, only a few studies focused on the clinical importance of FLT3 mutations in elderly AML patients, yielding conflicting results [3–7]. We analysed the frequency and prognostic impact of ITD and D835 mutations in a cohort of 120 consecutive elderly AML patients (except M3) seen at the Institute of Haematology, University ‘‘La Sapienza’’ of Rome, between January 2001 and December 2005. The diagnosis of AML was based on WHO criteria and morphological FAB classification. For all patients clinical and biological features at presentation (age, sex, WHO performance status, prior haematological disorder, fever and/or documented infection, percentage of BM and Pb blast cells, blood cell count, haemoglobin level, coagulation tests) were analysed as well as survival with respect to the presence or not of the FLT3 abnormalities. Whole BM samples of all patients were processed by a direct immunofluorescence staining technique and analysed utilizing a FACSCalibur Flow Cytometer (Becton Dickinson). Karyotypes were interpreted according to ISCN criteria and risk categories were considered as: high risk [presence of 75/del (5q), 77/del(7q), 3q abnormalities, t(6;9), t(9;22), complex changes ( 3)]; intermediate risk (karyotypes without a low or high risk constellation including abnormalities of 11q and normal karyotype); low risk [presence of t(8;21) and inv (16)]. For molecular analysis total RNA was extracted from the GTC lysate by using Chomczynsky and Sacchi method [8]. Two microlitres of cDNA were used for the amplification of different fusion genes (AML1ETO; CBFb-MYH11; BCR-ABLp190 and p210; DEK-CAN; MLL self fusion) according to previously reported standardised protocols [9]. Moreover, other 2 mL of cDNA were used in a multiplex PCR approach to amplify the FLT3 gene as reported elsewhere [10]. Statistical analysis was carried out using the SPSS software package. Prevalence of risk factors among patient groups was compared using w or Fisher’s exact test. Survival was defined as the