Effect of NPM1 and FLT3 mutations on the outcomes of elderly patients with acute myeloid leukemia receiving standard chemotherapy.

BACKGROUND: The effect of prognostically important gene mutations (MUTs), nucleophosmin (nucleolar phosphoprotein B23, numatrin) (NPM1) and fms-related tyrosine kinase 3 (FLT3), in elderly patients with acute myeloid leukemia (AML) is not well defined. PATIENTS AND METHODS: We analyzed 557 patients, 65 years of age or older with newly diagnosed AML, treated at our institution between 2000 and 2010 with cytotoxic chemotherapy. NPM1 and FLT3 analysis were available in 146 patients (26%) and 388 patients (70%), respectively. RESULTS: NPM1 and FLT3 MUTs occurred in 16% and 12% of patients, respectively. No difference in median overall survival was observed between FLT3-MUT and NPM1-MUT patients who received cytotoxic chemotherapy. Outcome was significantly better among patients with NPM1-MUT/FLT3-wild type (WT) genotype (n = 14) compared with patients carrying FLT3/NPM1 genotypes other than NPM1-MUT/FLT3-WT (n = 125). The complete remission rates were 71% and 49%, respectively (P = .11). The median survival was 21.5 months vs. 9.0 months and estimated 2-year survival rates were 51% vs. 38%, respectively (P = .003). NPM1 and FLT3 MUTs appear to occur less frequently in elderly AML patients. The prognostic effect of isolated NPM1- or isolated FLT3-MUT is minimal. CONCLUSION: Elderly AML patients with NPM1-MUT/FLT3-WT genotype have significantly improved outcomes compared with patients with other NPM1/FLT3 genotypes when treated with cytotoxic chemotherapy.

Prognostic impact of RAS mutations in patients with myelodysplastic syndrome.

RAS is an oncogene frequently mutated in human cancer. RAS mutations have been reported in 10-15% of cases of acute myeloid leukemia (AML) but they appear to be less frequent among patients with myelodysplastic syndrome (MDS). The impact of RAS mutations in patients with MDS is unclear. We conducted a retrospective study in 1,067 patients with newly diagnosed MDS for whom RAS mutational analysis was available. Overall, 4% of patients carried mutant RAS alleles. Notably, FLT3 mutations, which were found in 2% of patients, were mutually exclusive with RAS mutations. Patients with RAS mutations had a higher white blood cell count as well as bone marrow blasts compared with patients carrying wild-type RAS. However, no differences were observed between both groups regarding the risk of AML transformation (9% vs. 7%) and overall survival (395 days vs. 500 days, P = 0.057). In summary, RAS mutations are infrequent in patients with MDS and do not appear to negatively impact their outcome.

Analysis of the impact of imatinib mesylate therapy on the prognosis of patients with Philadelphia chromosome-positive chronic myelogenous leukemia treated with interferon-alpha regimens for early chronic phase.

BACKGROUND: The effect on prognosis of adding imatinib mesylate to the treatment of patients with Philadelphia chromosome (Ph)-positive chronic myelogenous leukemia (CML) has not been explored fully. The objective of the current study was to evaluate the benefit of adding imatinib to the treatment sequence of patients with early chronic phase Ph-positive CML who received interferon alpha (IFN)-based regimens as frontline therapy. METHODS: A total of 201 patients with early chronic phase Ph-positive CML who were treated on our 3 recent frontline IFN-based programs and were impacted early by the availability of sequential therapy with imatinib were analyzed. Their outcome was compared with that of a historical control group of 293 patients treated from 1982 until 1990 who were treated with IFN programs for early chronic phase CML and who did not have the opportunity of early access to imatinib (because it was not available during that period). Multivariate analysis was used to evaluate the independent effect of imatinib therapy on survival. RESULTS: Of 201 patients who were treated, 159 patients (79%) had their regimen changed sequentially to imatinib after a median duration of 14 months of IFN therapy. Of 139 patients who continued evaluation at our institution, 101 patients (73%; 64% of the total group) achieved a complete cytogenetic response, and 20 of 80 patients analyzed (25%; 10% of the total group) had no disease according to molecular studies (quantitative polymerase chain reaction studies). The estimated 5-year survival rate for the total study group of 201 patients was 86%. Survival of this group was significantly superior to the historic control group of IFN-treated patients who did not have the benefit of imatinib (P = 0.03). The trend also was observed within defined CML risk groups. Imatinib therapy was confirmed as an independent, significant, favorable prognostic factor for survival by multivariate analysis, after accounting for the independent prognostic effect of pretreatment prognostic factors (P = 0.005). CONCLUSIONS: The current analysis is the first to indicate the independent, favorable effect of imatinib on the survival of patients with Ph-positive CML.

A tyrosine kinase created by fusion of the PDGFRA and FIP1L1 genes as a therapeutic target of imatinib in idiopathic hypereosinophilic syndrome.

BACKGROUND: Idiopathic hypereosinophilic syndrome involves a prolonged state of eosinophilia associated with organ dysfunction. It is of unknown cause. Recent reports of responses to imatinib in patients with the syndrome suggested that an activated kinase such as ABL, platelet-derived growth factor receptor (PDGFR), or KIT, all of which are inhibited by imatinib, might be the cause. METHODS: We treated 11 patients with the hypereosinophilic syndrome with imatinib and identified the molecular basis for the response. RESULTS: Nine of the 11 patients treated with imatinib had responses lasting more than three months in which the eosinophil count returned to normal. One such patient had a complex chromosomal abnormality, leading to the identification of a fusion of the Fip1-like 1 (FIP1L1) gene to the PDGFRalpha (PDGFRA) gene generated by an interstitial deletion on chromosome 4q12. FIP1L1-PDGFRalpha is a constitutively activated tyrosine kinase that transforms hematopoietic cells and is inhibited by imatinib (50 percent inhibitory concentration, 3.2 nM). The FIP1L1-PDGFRA fusion gene was subsequently detected in 9 of 16 patients with the syndrome and in 5 of the 9 patients with responses to imatinib that lasted more than three months. Relapse in one patient correlated with the appearance of a T674I mutation in PDGFRA that confers resistance to imatinib. CONCLUSIONS: The hypereosinophilic syndrome may result from a novel fusion tyrosine kinase - FIP1L1-PDGFRalpha - that is a consequence of an interstitial chromosomal deletion. The acquisition of a T674I resistance mutation at the time of relapse demonstrates that FIP1L1-PDGFRalpha is the target of imatinib. Our data indicate that the deletion of genetic material may result in gain-of-function fusion proteins.