Current Opinion in Hematology:
Myeloid disease: Edited by Martin S. Tallman
Impact of new prognostic markers in treatment decisions in acute myeloid leukemia
Schlenk, Richard F; Döhner, Konstanze
Department of Internal Medicine III, University Hospital of Ulm, Ulm, Germany
Correspondence to Richard F. Schlenk, MD, Department of Internal Medicine III, University Hospital of Ulm, Albert Einstein Allee 23, 89081 Ulm, Germany Tel: +49 731 500 45900; fax: +49 731 500 45905; e-mail: firstname.lastname@example.org
Purpose of review: In recent years, new molecular markers have emerged as significant prognostic parameters and as potential targets for molecularly targeted therapy in acute myeloid leukemia (AML). However, prognostic markers cannot guide the decision for a specific treatment, as they are associated with a differential outcome regardless of the given treatment. In contrast, predictive markers indicate a treatment benefit in patients that are characterized through these markers. Thus, predictive markers can guide clinical decision-making.
Recent findings: In young adults, mutations of the nucleophosmin (gene 9NPM1mut) in the absence of concurrent FLT3-internal tandem duplication (ITD) (FLT3-ITDneg) have impressive prognostic and, beyond prognostication, predictive properties. This NPM1mut/FLT3-ITDneg genotype predicts equivalent favorable outcome after intensive chemotherapy and allogeneic stem cell transplantation, whereas in the absence of this marker clinical outcome was significantly improved after an allogeneic transplantation. In addition, within a retrospective study performed on older adults, the same genotype predicted a significantly improved outcome if all-trans retinoic acid was added to intensive chemotherapy.
Summary: The discovery of new prognostic and predictive markers has increased our understanding of leukemogenesis and this may lead to improved prognostication and, more important, to novel genotype-specific treatment strategies.
Pretreatment genetic aberrations in leukemic cells are one of the most powerful prognostic parameters in acute myeloid leukemia (AML) [1–5,6•,7•]. In recent years, a number of submicroscopic gene mutations as well as deregulated gene expression have been identified, especially, in the large subgroup of patients exhibiting a normal karyotype [cytogenetically normal (CN)-AML] [6•]. The prognostic value of cytogenetic aberrations, gene mutations, and deregulated genes in AML has been evaluated almost exclusively in retrospective studies and, therefore, cautious interpretation of results and in consequence their clinical impact is necessary. Furthermore, prognostic markers are not per se usable for clinical decision-making in that they are associated with a differential outcome regardless of the treatment given [8,9]. In contrast, markers attributing the clinical benefit of a specific treatment to AML patients who are characterized by the marker status are termed predictive markers . From a statistical purist's point of view, only predictive markers can be used for clinicians in therapeutic decision-marking.
In this article, we first discuss some statistical aspects that have to be considered for the interpretation of results from retrospective studies and, thereafter, the discovery of novel prognostic and predictive markers in AML.
The interpretation of results from prognostic and predictive marker studies depends to a great extent on the internal and external validity of the data. The validity of results is improved by addressing potential sources of bias and using appropriated statistical methods.
Potential sources of bias
In contrast to controlled clinical trials, in which the patient population is clearly defined by inclusion and exclusion criteria, in most prognostic molecular marker studies selection bias remains an issue. The patient population in prognostic marker studies was mostly derived from a combination of several clinical trials and the main inclusion criteria for the marker studies is the availability of pretreatment peripheral blood, bone marrow samples, or both. As a consequence of this, leukemia specimens with low cell counts will be archived less frequently for further genetic analysis as compared with cell-rich samples. This fact is reflected by the observation that in AML prognostic marker studies [10••,11••], the analyzed patient populations are frequently characterized by higher white blood cell (WBC) counts. These sources of bias can be addressed by stating the proportion of patients with available samples in relation to those without samples and by a comparison for the clinical endpoints and important covariates used in the study between the groups of patients with and without available samples. By these two simple methods, the readers are put into a position to assess whether results can be generalized to all AML patients or rather the results are valid only for the subset of patients analyzed in the particular study.
Appropriate statistical methods
For the assessment of new prognostic and predictive markers, multivariable regression analyses are a conditio sine qua non because they allow evaluation of the impact of new markers in relation to already known markers. However, selection of variables for the presented model impacts heavily on the obtained results and therefore the methodology of variable selection has to be taken into account for the clinical interpretation of the results. In addition, in most studies, clinical datasets are incomplete. It is important to address the issue of missing data when developing prognostic models. The procedure to exclude those individuals whose data are incomplete from the analyses is not recommended, because this practice is inefficient, leading to a reduction in statistical power and, more importantly, to biased results and massive overestimation of odds and hazard ratios . Since its introduction nearly 30 years ago, multiple imputation has become an important and influential approach in the statistical analysis of incomplete data and the methodology has been recently reviewed [13•].
Mutations in the nucleophosmin gene
Nucleophosmin (NPM1) is a highly conserved phosphoprotein that physiologically resides in nucleoli and shuttles between nucleus and cytoplasm. It is involved in several cellular processes such as ribosome biogenesis, response to stress stimuli, maintenance of genomic stability, regulation of activity and stability of tumor-suppressor genes such as p53 and ARF, and transcriptional regulation . Falini et al.  first discovered the abnormal cytoplasmic localization of NPM1 that is caused by mutations in exon 12 of the gene. Subsequent studies revealed that cytoplasmic accumulation of NPM1 mutants results from two major alterations acting in concert, loss of tryptophan residues normally required for NPM1 binding to the nucleoli and generation of an additional export signal motif at the C-terminus [16•]. In addition, NPM1 leukemic mutants were shown to recruit wild-type NPM1 from nucleoli to nucleoplasm and cytoplasm through dimerization [16•]. Mutations of the NPM1 gene are the most frequent genetic aberration in adult AML detectable in 24–35% of all cases [15,17–19] and in 43–62% of cases exhibiting a normal karyotype [10••,15,17–21,22•,23•]. In childhood AML, the incidence of NPM1 mutations is much lower at 8%, and NPM1 mutations are age dependent in that they are found in older children (median 10.9 years) and not seen in pediatric patients below the age of 3 years [24•]. In adult AML, the incidence of NPM1 mutation increases with age [25•] until the age of 60 years and, thereafter, seems to slightly decrease [22•]. Clinically, NPM1 mutations are associated with specific features, including predominance of female sex, higher bone marrow blast percentages, lactate dehydrogenase levels, WBC and platelet counts, and high CD33 but low or absent CD34 antigen expression. Of note, NPM1 mutations are significantly associated with cytogenetics in that more than 85% occur in CN-AML patients [10••,15,17–21,22•–24•]. The differences in clinical characteristics at diagnosis between NPM1mut and NPM1wt AML are not only related to the NPM1 mutational status but also to the interaction with cooperating gene mutations such as FLT3-internal tandem duplication (ITD) .
Mutations in the FMS-like tyrosine kinase 3 gene
FMS-like tyrosine kinase 3 (FLT3) is a member of the class III receptor tyrosine kinase family that is normally expressed on the surface of hematopoietic progenitor cells. FLT3 and its ligand play an important role in proliferation, survival, and differentiation of multipotent stem cells. The gene that encodes FLT3 is localized on chromosome 13q12, containing 24 exons. In AML patients, somatic mutations that result in the constitutive activation of FLT3 have been identified in two functional domains of the receptor, the juxtamembrane domain and the activation loop of the tyrosine kinase domain (TKD) [26,27]. The juxtamembrane domain that has been shown to be crucial for kinase autoinhibition is disrupted by ITDs in 28–34% of CN-AML cases, whereas juxtamembrane domain point mutations occur less frequently [27–29]. FLT3-ITDs are located in exons 14 and 15 and vary in insertion site and length of the duplicated segment (from three to 400 nucleotides). Mutations occurring in the activation loop in the carboxy-terminal lobe of the TKD are usually point mutations, small insertions, or deletions mainly involving codons 835 (D835) and 836 (I836) in 11–14% of CN-AML patients [28,29,30•]. However, additional point mutations or insertions affecting other codons in the TKD have been reported in single AML cases. In-vitro studies and results from global gene expression profiling revealed that there are not only similarities but also important differences in signal transduction properties between FLT3-ITDs and TKD mutations that may explain differences in clinical phenotypes [31•]. AML patients harboring a FLT3-ITD are characterized by certain pretreatment features such as increased WBC count, higher percentages of blood and bone marrow blasts, and a more frequent diagnosis of de novo rather than secondary AML .
Mutations in the CCAAT enhancer-binding protein alpha gene
The transcription factor CCAAT enhancer-binding protein alpha (CEBPA) is a key molecule in the mediation of lineage specification and differentiation of multipotent myeloid progenitors into mature neutrophils . CEBPA mutations were first discovered in 2001 and the majority of the mutated patients have normal cytogenetics. There are two major types of CEBPA mutations; nonsense mutations affecting the N-terminal region of the molecule preventing expression of the full-length CEBPA protein, thereby upregulating the formation of a truncated isoform with dominant negative properties, and in-frame mutations in the C-terminal basic region-leucine zipper domain resulting in CEBPA protein with decreased DNA binding or dimerization activity. N and C-terminal mutations often occur simultaneously, either affecting the same (monoallelic) or different (biallelic) alleles. CN-AML patients carrying a CEBPA mutation are characterized by distinct clinical features such as higher peripheral blood blast counts, lower platelet counts, less lymphadenopathy, or extramedullary leukemia and CEBPA mutations are less frequently associated with FLT3-ITD or TKD mutations .
Prognostic and predictive value of the nucleophosmin, FMS-like tyrosine kinase 3, CCAAT enhancer-binding protein alpha genotypes
NPM1mut has consistently been reported as a favorable prognostic marker for achievement of a complete remission after intensive induction therapy, either as a single marker [15,21,22•,23•] or in combination with the FLT3-ITD in that a favorable response was only seen in patients with the combined genotype NPM1mut/FLT3-ITDneg [10••,19,20]. Actually, no data are available attributing the favorable impact of NPM1mut to induction success to specific chemotherapeutic agents or strategies.
NPM1mut has also been reported as a favorable prognostic marker for relapse-free survival (RFS) and overall survival (OS). In most reports, this favorable impact on survival endpoints was evident in the genotype NPM1mut/FLT3-ITDneg, whereas the unfavorable prognosis of patients with the genotype NPM1mut/FLT3-ITDpos was mainly determined by the negative impact of FLT3-ITD [10••,19–21,22•,23•]. The favorable outcome of patients with the genotype NPM1mut/FLT3-ITDneg was achieved not only after intensive consolidation chemotherapy but also after autologous or allogeneic blood stem cell transplantation (SCT). However, there is some controversy about the value of allogeneic SCT in first complete remission in patients with the favorable genotype NPM1mut/FLT3-ITDneg. In a large individual patient data meta-analysis [10••] focused on patients with CN-AML, the favorable genotype NPM1mut/FLT3-ITDneg could be established as a predictive marker for RFS in that patients exhibiting this genotype did not benefit from an allogeneic SCT in first complete remission. In contrast, in the subgroup of patients defined either by FLT3-ITDpos as a single marker or by the genotype NPM1WT/FLT3-ITDneg/CEBPAWT, an allogeneic SCT led to a 40% reduction in the risk of relapse or death. Of note, in this meta-analysis of four prospective clinical trials, allogeneic SCT was restricted to matched family donors and the allocation to an allogeneic SCT was strictly based on a so-called genetic randomization [34•]. The benefit in RFS did not translate into a significantly better OS, which was mainly due to the excellent outcome of relapsed patients after a matched unrelated donor SCT. These results strongly argue for an allogeneic SCT from a matched related and probably also unrelated donor in first complete remission in AML with these high-risk genotypes [10••]. Very similar data were reported by Bornhäuser et al. [35•], who showed a lower relapse rate in FLT3-ITDpos patients after SCT; however, in this study, uncontrolled selection bias relativizes the results in that allocation to the treatment strategies was performed in a prioritized rather than a randomized manner with first priority for allogeneic SCT, second priority for autologous SCT, and finally, if the other strategies had not been feasible, chemotherapy. In contrast, Gale et al.  found no beneficial effect of an allogeneic SCT in AML defined by the single marker FLT3-ITDpos. However, their data were hampered by a low adherence to the protocol with only 63% of the patients receiving the allocated allogeneic SCT, a high treatment-related mortality of 30% after allogeneic SCT, and an enormous potential selection bias due to the fact that only about one-third of the total clinical trial population (MRC AML-10 and AML-12 trials) has been analyzed.
Approximately 11–15% of NPM1 mutations are detected in combination with various recurring cytogenetic abnormalities, raising the question as to whether NPM1 mutant AML defines a distinct biological and clinical entity [18,19,25•,37]. This question might gain further importance when a targeted therapy becomes available for NPM1mut AML. In a more recent study , NPM1 was shown to act as a corepressor in retinoic acid-associated transcriptional regulation in a manner such that during retinoic acid-induced cellular differentiation, activating protein transcription factor 2 (AP2) recruits NPM1 to the promoter of certain retinoic acid-responsive genes. The German–Austrian AML Study Group (AMLSG) reported on a beneficial effect of all-trans retinoic acid (ATRA) given as adjunct to conventional chemotherapy on complete remission rate, event-free survival, and OS in elderly patients with nonacute promyelocytic (non-APL) AML . Interestingly, in retrospective analyses, it could be shown that the beneficial effect of ATRA in this trial was restricted to patients whose leukemic cells exhibited the genotype NPM1mut/FLT3-ITDneg [22•]. So the genotype NPM1mut/FLT3-ITDneg appears as a predictive marker for the beneficial effect of ATRA in non-APL AML. Although this analysis is retrospective in nature, the fact that the AMLHD98B trial was a randomized trial reduces selection bias. In addition, AMLSG is currently validating these findings in a separate patient population within the ongoing prospective AMLSG 07-04 trial (clinicaltrials.gov, NCT00151242), which randomizes for ATRA in younger adults.
The high CD33 expression in NPM1mut AML specifically points to gemtuzumab ozogamicin as a targeted therapy, especially on the basis of new data showing a positive correlation between expression level and response to gemtuzumab ozogamicin [40•]. Actually, no data evaluating the specific impact of gemtuzumab ozogamicin in this molecularly defined subgroup of AML patients are available.
FLT3-ITD has been reported consistently as an unfavorable prognostic marker for RFS and OS [23•,27–29]. Whether other molecular markers, in particular NPM1mut, add to prognostication in FLT3-ITDpos AML is unclear. Gale et al. [23•] claimed a more favorable prognosis for patients with the genotype NPM1mut/FLT3-ITDpos compared with those with the genotype NPM1WT/FLT3-ITDpos; however, these findings could not be confirmed by several other studies [10••,19]. More recent data provide evidence that outcome is also related to the level of the mutant allele, and not just its mere presence [23•,29,41]. However, if NPM1 mutation status was added to the prognostic model in these studies, the mutant wild-type ratio of FLT3-ITD was no longer considered as prognostic [19,23•]. At present, mutant wild-type ratio (high versus low) is used within the up-front randomized multicenter phase III trial [Cancer and Leukemia Group B (CALGB) 10603; clinicaltrials.gov, NCT00651261] for stratified randomization of midostaurin (PKC412) in young adult AML patients. This study is based on the favorable phase I/II studies in FLT3-mutated AML suggesting a clinical efficacy of FLT3 inhibitors especially in combination with standard chemotherapy [42,43].
In contrast to FLT3-ITD mutations, the prognostic significance of FLT3-TKDmut is still controversial. A previous meta-analysis  on 1160 cases including FLT3-TKDmut cases (n = 84) showed a negative prognostic impact of TKD mutations. However, no subset analysis for CN-AML patients was performed. In contrast, a study [30•] performed by the British MRC group on 1107 young adults showed a positive impact of FLT3-TKDmut on RFS and OS, especially if patients had a high allelic wild-type/mutant ratio. Of note, in the study from the MRC, there was a large potential selection bias starting from 3803 patients who were treated in the MRC trials AML-10 and AML-12 and only 1107 patients who had been finally analyzed (29%). In addition, other gene mutations, in particular NPM1 mutations, have not been taken into account for multivariate analysis. In a study by Bacher et al. [45•] and Schlenk et al. [10••], the interaction of FLT3-TKDmut with NPM1mut has been addressed showing a favorable prognosis for the genotype NPM1mut/FLT3-TKDmut in the absence of an FLT3-ITD. This is in contrast to a study [31•] from CALBG revealing a negative prognostic impact of FLT3-TKDmut irrespective of the NPM1 status. However, in the large meta-analysis [10••] of CN-AML, FLT3-TKDmut did not impact on RFS and OS in multivariable analysis. The prognostic value of FLT3-TKDmut that also occurs in patients with favorable cytogenetics, in particular with inv(16), remains to be determined. At present, patients with FLT3-ITD, FLT3-TKDmut or both are eligible for the inclusion into FLT3-inhibitor trials (CALGB 10603; clinicaltrials.gov, NCT00651261). Data from these trials will probably show in the future whether FLT3-TKDmut will become a predictive marker for the treatment with these agents.
CEBPA mutations consistently have been associated with a favorable prognosis, either in the subset of patients with intermediate-risk cytogenetics [46,47] or in patients with normal karyotypes [10••,33,48•]. In the context of other molecular markers, the genotype CEBPAmut retained its prognostic importance for RFS and OS; additional mutations did not affect outcome in the CEBPAmut subgroup [10••]. Actually, even in the largest cohort of patients analyzed so far in CN-AML, the sample size in the CEBPAmut subgroup was too low for meaningful analysis, in particular to compare the different postremission strategies (chemotherapy versus autologous SCT versus allogeneic SCT) [10••]. Therefore, the prognostic marker CEBPAmut cannot actually be used as a predictive marker.
Other gene mutations
The partial tandem duplication (PTD) of the myeloid/lymphoid or mixed lineage leukaemia (MLL) gene was the first gene mutation shown to affect prognosis in CN-AML patients . MLL-PTD is mainly found in CN-AML with an incidence ranging from 5 to 11%. There are no clinical features distinguishing MLL-PTD-positive from MLL wild-type patients [50,51]. Approximately 30–40% of MLL-PTD-positive patients also harbor FLT3-ITD mutations, whereas coexistence with CEBPA or NPM1 mutations is rare [10••]. MLL-PTD has been associated with shorter complete remission duration or worse RFS; however, in these studies, MLL-PTD had no effect on OS. [10••,50,51]. Recently, the CALGB [52•] reported on the impact of MLL-PTD in a large cohort of younger adult patients who received autologous SCT in first complete remission. Clinical outcome did not differ between the MLL-PTD-positive and the MLL wild-type group. Although the authors suggested that intensive consolidation therapy using autologous SCT might improve outcome in this subgroup of patients, this study did not provide direct evidence for this.
RAS oncogenes represent a family of membrane-associated proteins that adjust signal transduction upon binding of ligands to a variety of membrane receptors. They regulate mechanism of proliferation, differentiation, and apoptosis. Two large studies [53,54] in AML patients described RAS mutations in 10.3–13.6% of adult AML patients. Of note, the frequency of RAS mutations was highest in patients exhibiting an inv(16) at diagnosis. Consistent with previous reports, there was no prognostic impact of RAS mutations. More recently, Neubauer et al. [55•] showed a predictive impact of RAS mutations in that patients receiving high-dose cytarabine in consolidation therapy had a significantly lower probability of relapse as compared with patients receiving standard dose cytarabine and this effect holds if adjustment for cytogenetics, in particular inv(16), has been performed. Although this is a retrospective analysis, the randomization of the initial trial valorizes the results. In addition, RAS mutations may provide a target for molecular therapy.
Mutations in the Wilms' tumor suppressor 1 gene (WT1) in AML were first reported by King-Underwood et al. in 1996 . In more recent studies [11••,57•] (Gaidzik V, et al., in preparation), WT1 mutations have been identified with an incidence of 10–12.6% in CN-AML. However, inconsistent results have been reported about the prognostic impact of WT1 mutations. Both CALGB and MRC studies evaluated the prognostic significance of WT1 mutations in younger adults with CN-AML. In both studies, patients with WT1 mutations had inferior RFS and OS, and in multivariable analysis, WT1 mutation was an independent adverse prognostic factor. This is in contrast to the findings of Gaidzik et al. (in preparation) who did not observe any prognostic impact of WT1 mutations on RFS and OS in either univariable or multivariable analysis. Of note, when performing exploratory subset analysis that takes into account the FLT3-ITD status, the WT1mut/FLT3-ITDpos genotype appeared to be associated with worse clinical course. One major difference between the three studies relates to treatment in that the cumulative dose of cytarabine was significantly higher in the trial reported by Gaidzik et al. (in preparation), suggesting that the negative impact of WT1 mutations reported by others may be overcome by the use of repetitive cycles of high-dose cytarabine. On the basis of the current data, the prognostic impact of WT1 mutation remains unclear and the potential interrelationship to treatment has to be addressed in future studies.
In AML, novel molecular markers of prognostic and more importantly of predictive significance have been discovered. The link between the leukemogenic importance of these markers and their role as potential targets for old and novel drugs will contribute to the stepwise replacement of risk adapted by genotype-specific treatment strategies. This development will necessitate large collaborative group efforts to perform clinical trials even in small genetic subgroups.
Supported by grants from the Bundesministerium für Bildung und Forschung (01GI9981 and 01KG0605), the Deutsche José Carreras Leukämie–Stiftung (DJCLS R06/06v), and the Else Kröner-Fresenius-Stiftung (P38/05//A49/05//F03).
There are no conflicts of interest.
References and recommended reading
Papers of particular interest, published within the annual period of review, have been highlighted as:
• of special interest
•• of outstanding interest
Additional references related to this topic can also be found in the Current World Literature section in this issue (p. 150).
1 Grimwade D, Walker H, Oliver F, et al. The importance of diagnostic cytogenetics on outcome in AML: analysis of 1612 patients entered into the MRC AML 10 trial. The Medical Research Council Adult and Children's Leukaemia Working Parties. Blood 1998; 92:2322–2333.
2 Byrd JC, Mrózek K, Dodge RK, et al, Cancer and Leukemia Group B (CALGB 8461). Pretreatment cytogenetic abnormalities are predictive of induction success, cumulative incidence of relapse, and overall survival in adult patients with de novo acute myeloid leukemia: results from Cancer and Leukemia Group B (CALGB 8461). Blood 2002; 100:4325–4336.
3 Grimwade D, Walker H, Harrison G, et al. The predictive value of hierarchical cytogenetic classification in older adults with acute myeloid leukemia (AML): analysis of 1065 patients entered into the United Kingdom Medical Research Council AML11 trial. Blood 2001; 98:1312–1320.
4 Fröhling S, Schlenk RF, Kayser S, et al. Cytogenetics and age are major determinants of outcome in intensively treated acute myeloid leukemia patients older than 60 years: results from AMLSG trial AML HD98-B. Blood 2006; 108:3280–3288.
5 Mrózek K, Döhner H, Bloomfield CD. Influence of new molecular prognostic markers in patients with karyotypically normal acute myeloid leukemia: recent advances. Curr Opin Hematol 2007; 14:106–114.
6• Gaidzik V, Döhner K. Prognostic implications of gene mutations in acute myeloid leukemia with normal cytogenetics. Semin Oncol 2008; 35:346–355.
7• Breems DA, Van Putten WL, De Greef GE, et al. Monosomal karyotype in acute myeloid leukemia: a better indicator of poor prognosis than a complex karyotype. J Clin Oncol 2008; 26:4791–4797.
8 Simon R, Altman DG. Statistical aspects of prognostic factor studies in oncology. Br J Cancer 1994; 69:979–985.
9 Sargent DJ, Conley BA, Allegra C, Collette L. Clinical trial designs for predictive marker validation in cancer treatment trials. J Clin Oncol 2005; 23:2020–2027.
10•• Schlenk RF, Döhner K, Krauter J, et al. Mutations and treatment outcome in cytogenetically normal acute myeloid leukemia. N Engl J Med 2008; 358:1909–1918.
11•• Virappane P, Gale R, Hills R, et al. Mutation of the Wilms' tumor 1 gene is a poor prognostic factor associated with chemotherapy resistance in normal karyotype acute myeloid leukemia: the United Kingdom Medical Research Council Adult Leukaemia Working Party. J Clin Oncol 2008; 26:5429–5435.
12 Harrell FE. Regression modeling strategies: with applications to linear models, logistic regression, and survival analysis. New York, New York: Springer Verlag; 2001.
13• Kenward MG, Carpenter J. Multiple imputation: current perspectives. Stat Methods Med Res 2007; 16:199–218.
14 Grisendi S, Mecucci C, Falini B, et al. Nucleophosmin and cancer. Nat Rev 2006; 6:493–505.
15 Falini B, Mecucci C, Tiacci E, et al, Gimema Acute Leukemia Working Party. Cytoplasmic nucleophosmin in acute myelogenous leukemia with a normal karyotype. N Engl J Med 2005; 352:254–266.
16• Falini B, Nicoletti I, Martelli MF, et al. Acute myeloid leukemia carrying cytoplasmic/mutated nucleophosmin (NPMc_ AML): biological and clinical features. Blood 2007; 109:874–885. This study is an excellent review of the biology of NPM1mut AML.
17 Suzuki T, Kiyoi H, Ozeki K, et al. Clinical characteristics and prognostic implications of NPM1 mutations in acute myeloid leukemia. Blood 2005; 106:2854–2861.
18 Verhaak RG, Goudswaard CS, van Putten W, et al. Mutations in nucleophosmin (NPM1) in acute myeloid leukemia (AML): association with other gene abnormalities and previously established gene expression signatures and their favorable prognostic significance. Blood 2005; 106:3747–3754.
19 Thiede C, Koch S, Creutzig E, et al. Prevalence and prognostic impact of NPM1 mutations in 1485 adult patients with acute myeloid leukemia (AML). Blood 2006; 107:4011–4020.
20 Döhner K, Schlenk RF, Habdank M, et al. Mutant nucleophosmin (NPM1) predicts favorable prognosis in younger adults with acute myeloid leukemia and normal cytogenetics: interaction with other gene mutations. Blood 2005; 106:3740–3746.
21 Schnittger S, Schoch C, Kern W, et al. Nucleophosmin gene mutations are predictors of favorable prognosis in acute myelogenous leukemia with a normal karyotype. Blood 2005; 106:3733–3739.
22• Schlenk RF, Döhner K, Kneba M, et al. Gene mutations and response to treatment with all-trans retinoic acid in elderly patients with acute myeloid leukemia: results from AMLSG Trial AML HD98B. Haematologica 2009; 94:54–60.
23• Gale RE, Green C, Allen C, et al. The impact of FLT3 internal tandem duplication mutant level, number, size, and interaction with NPM1 mutations in a large cohort of young adult patients with acute myeloid leukemia. Blood 2008; 111:2776–2784.
24• Brown P, McIntyre E, Rau R, et al. The incidence and clinical significance of nucleophosmin mutations in childhood AML. Blood 2007; 110:979–985.
25• Liso A, Castiglione F, Cappuccio A, et al. A one-mutation mathematical model can explain the age incidence of acute myeloid leukemia with mutated nucleophosmin (NPM1). Haematologica 2008; 93:1219–1226.
26 Yamamoto Y, Kiyoi H, Nakano Y, et al. Activating mutation of D835 within the activation loop of FLT3 in human hematologic malignancies. Blood 2001; 97:2434–2439.
27 Kottaridis PD, Gale RE, Frew ME, et al. The presence of a FLT3 internal tandem duplication in patients with acute myeloid leukemia (AML) adds important prognostic information to cytogenetic risk group and response to the first cycle of chemotherapy: analysis of 854 patients from the United Kingdom Medical Research Council AML 10 and 12 trials. Blood 2001; 98:1752–1759.
28 Fröhling S, Schlenk RF, Breitruck J, et al. Prognostic significance of activating FLT3 mutations in younger adults (16 to 60 years) with acute myeloid leukemia and normal cytogenetics: a study of the AML Study Group Ulm. Blood 2002; 100:4372–4380.
29 Thiede C, Steudel C, Mohr B, et al. Analysis of FLT3-activating mutations in 979 patients with acute myelogenous leukemia: association with FAB subtypes and identification of subgroups with poor prognosis. Blood 2002; 99:4326–4335.
30• Mead AJ, Linch DC, Hills RK, et al. FLT3 tyrosine kinase domain mutations are biologically distinct from and have a significantly more favorable prognosis than FLT3 internal tandem duplications in patients with acute myeloid leukemia. Blood 2007; 110:1262–1270.
31• Whitman SP, Ruppert AS, Radmacher MD, et al. FLT3 D835/I836 mutations are associated with poor disease free survival and a distinct gene-expression signature among younger adults with de novo cytogenetically normal acute myeloid leukemia lacking FLT3 internal tandem duplication. Blood 2008; 111:1552–1559.
32 Pabst T, Mueller BU, Zhang P, et al. Dominant-negative mutations of CEBPA, encoding CCAAT/enhancer binding protein-alpha (C/EBPalpha), in acute myeloid leukemia. Nat Genet 2001; 3:263–270.
33 Fröhling S, Schlenk RF, Stolze I, et al. CEBPA mutations in younger adults with acute myeloid leukemia and normal cytogenetics: prognostic relevance and analysis of cooperating mutations. J Clin Oncol 2004; 22:624–633.
34• Büchner T, Berdel WE, Kienast J, et al. Cytogenetically normal acute myeloid leukemia. N Engl J Med 2008; 359:651–653.
35• Bornhäuser M, Illmer T, Schaich M, et al. Improved outcome after stem-cell transplantation in FLT3/ITD-positive AML. Blood 2007; 109:2264–2265.
36 Gale RE, Hills R, Kottaridis PD, et al. No evidence that FLT3 status should be considered as an indicator for transplantation in acute myeloid leukemia (AML): an analysis of 1135 patients, excluding acute promyelocytic leukemia, from the UK MRC AML10 and 12 trials. Blood 2005; 106:3658–3665.
37 Arber DA, Vardiman JW, Brunning RD, et al. Acute myeloid leukaemia with recurrent genetic abnormalities. In: Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, Thiele J, Vardiman JW, editors. WHO classification of tumours of haematopoietic and lymphoid tissues. 4th ed. Geneva, Switzerland: WHO Press; 2008. pp. 120–122.
38 Liu H, Tan BC, Tseng KH, et al. Nucleophosmin acts as a novel AP2alpha-binding transcriptional corepressor during cell differentiation. EMBO Rep 2007; 8:394–400.
39 Schlenk RF, Fröhling S, Hartmann F, et al. Phase III study of all-trans retinoic acid in previously untreated patients 61 years or older with acute myeloid leukemia. Leukemia 2004; 18:1798–1803.
40• Walter RB, Gooley TA, van der Velden VH, et al. CD33 expression and P-glycoprotein-mediated drug efflux inversely correlate and predict clinical outcome in patients with gemtuzumab ozogamicin monotherapy. Blood 2007; 109:4168–4170.
41 Whitman SP, Archer KJ, Feng L, et al. Absence of the wild-type allele predicts poor prognosis in adult de novo acute myeloid leukemia with normal cytogenetics and the internal tandem duplication of FLT3: a Cancer and Leukemia Group B study. Cancer Res 2001; 61:7233–7239.
42 Stone R, Fischer T, Paquette R, et al. Phase IB study of PKC412, an oral FLT3 kinase inhibitor, in sequential and simultaneous combinations with daunorubicin and cytarabine (DA) induction and high-dose cytarabine consolidation in newly diagnosed adult patients (pts) with acute myeloid leukemia (AML) under age 61 [abstract]. Blood 2006; 108:157.
43 Levis M, Smith BD, Beran M, et al. A randomized, open-label study of lestaurtinib (CEP-701), an oral FLT3 inhibitor, administered in sequence with chemotherapy in patients with relapsed AML harboring FLT3 activating mutations: clinical response correlates with successful FLT3 inhibition [abstract]. Blood 2005; 106:403.
44 Yanada M, Matsuo K, Suzuki T, et al. Prognostic significance of FLT3 internal tandem duplication and tyrosine kinase domain mutations for acute myeloid leukemia: a meta-analysis. Leukemia 2005; 19:1345–1349.
45• Bacher U, Haferlach C, Kern W, et al. Prognostic relevance of FLT3-TKD mutations in AML: the combination matters: an analysis of 3082 patients. Blood 2008; 111:2527–2537.
46 Preudhomme C, Sagot C, Boissel N, et al. Favorable prognostic significance of CEBPA mutations in patients with de novo acute myeloid leukemia: a study from the Acute Leukemia French Association (ALFA). Blood 2002; 100:2717–2723.
47 Barjesteh van Waalwijk van Doorn-Khosrovani S, Erpelinck C, Meijer J, et al. Biallelic mutations in the CEBPA gene and low CEBPA expression levels as prognostic markers in intermediate-risk AML. Hematol J 2003; 4:31–40.
48• Marcucci G, Maharry K, Radmacher MD, et al. Prognostic significance of, and gene and microRNA expression signatures associated with, CEBPA mutations in cytogenetically normal acute myeloid leukemia with high-risk molecular features: a Cancer and Leukemia Group B Study. J Clin Oncol 2008; 26:5078–5087.
49 Caligiuri MA, Strout MP, Lawrence D, et al. Rearrangement of ALL1 (MLL) in acute myeloid leukemia with normal cytogenetics. Cancer Res 1998; 58:55–59.
50 Döhner K, Tobis K, Ulrich R, et al. Prognostic significance of partial tandem duplications of the MLL gene in adult patients 16 to 60 years old with acute myeloid leukemia and normal cytogenetics: a study of the AML Study Group ULM (AMLSG Ulm). J Clin Oncol 2002; 20:3254–3261.
51 Stirewalt DL, Kopecky KJ, Meshinchi S, et al. FLT3, RAS and TP53 mutations in elderly patients with acute myeloid leukemia. Blood 2001; 97:3589–3595.
52• Whitman SP, Ruppert AS, Marcucci G, et al. Long-term disease-free survivors with cytogenetically normal acute myeloid leukemia and MLL partial tandem duplication: a Cancer and Leukemia Group B study. Blood 2007; 109:5164–5167.
53 Bacher U, Haferlach T, Schoch C, et al. Implication of NRAS mutations in AML: a study of 2502 patients. Blood 2006; 107:3847–3853.
54 Bowen DT, Frew ME, Hills R, et al. RAS mutation in acute myeloid leukemia is associated with distinct cytogenetic subgroups but does not influence outcome in patients younger than 60 years. Blood 2005; 106:2113–2119.
55• Neubauer A, Maharry K, Mrózek K, et al. Patients with acute myeloid leukemia and RAS mutations benefit most from postremission high-dose cytarabine: a Cancer and Leukemia Group B study. J Clin Oncol 2008; 26:4603–4609.
56 King-Underwood L, Renshaw J, Pritchard-Jones K. Mutations in the Wilms' tumor gene WT1 in leukemias. Blood 1996; 87:2171–2179.
57• Paschka P, Marcucci G, Ruppert AS, et al. Wilms' tumor 1 gene mutations independently predict poor outcome in adults with cytogenetically normal acute myeloid leukemia: a cancer and leukemia group B study. J Clin Oncol 2008; 26:4595–4602.
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