- Email: [email protected]
FLT3-TKD Mutations Associated With NPM1 Mutations Define a Favorable-risk Group in Patients With Acute Myeloid Leukemia
Original Study
FLT3-TKD Mutations Associated With NPM1 Mutations Define a Favorable-risk Group in Patients With Acute Myeloid Leukemia Marielle Perry,1 Sarah Bertoli,2 Clément Rocher,1 Sandrine Hayette,3 Sophie Ducastelle,1 Fiorenza Barraco,1 Hélène Labussière-Wallet,1 Gilles Salles,1,4 Christian Recher,2 Xavier Thomas,1 Etienne Paubelle1,4,5 Abstract The outcome of patients with mutation of the FLT3 tyrosine kinase domain (FLT3-TKD) in acute myeloid leukemia (AML) remains controversial. We present a retrospective study of 126 newly diagnosed patients with AML. Our data suggest that FLT3-TKD mutations should be routinely determined at the time of diagnosis. FLT3-TKD in association with NPM1 mutations define a favorable-risk group in patients with AML. Background: Outcome of patients with mutation of the FLT3 tyrosine kinase domain (FLT3-TKD) in acute myeloid leukemia (AML) remains controversial. Patients and Methods: Herein, we present a retrospective study of 126 newly diagnosed patients with AML performed in 2 French centers. Results: FLT3-TKD mutations represented 12.7% of patients, whereas FLT3-internal tandem duplication (ITD) mutation was observed in 20.6% of AML cases and 1.6% of patients harbored both anomalies. At diagnosis, FLT3-TKD and FLT3-ITD were associated with higher peripheral leukocytes count and a higher blast count in bone marrow (P < 10-4). Mutations of the NPM1 gene were frequently associated to FLT3-TKD (68.7%) and FLT3-ITD (61.5%) mutations compared with FLT3 wild type (WT) patients (P < 10-4). Patients with both FLT3-TKD and NPM1 mutations (n ¼ 12; 9.5%) showed a favorable outcome. Interestingly, mutations in NPM1 gene lost their favorable prognostic when not associated with FLT3-TKD both in univariate and multivariate analyses. Conclusion: Our data suggest that FLT3-TKD mutations should be routinely determined at the time of diagnosis. In association with NPM1 mutations, patients should follow the therapeutic schedule of favorable-risk patients with AML. Clinical Lymphoma, Myeloma & Leukemia, Vol. 18, No. 12, e545-50 ª 2018 Elsevier Inc. All rights reserved. Keywords: Chemotherapy, Favorable risk-group, FLT3-ITD mutation, Prognosis
Introduction Acute myeloid leukemia (AML) is an aggressive malignant disease affecting 2.5 to 3.5 per 100,000 adults each year in the 1 Department of Hematology, Hospices Civils de Lyon, Centre Hospitalier Lyon Sud, Pierre-Bénite, France 2 Department of Hematology, Institut Universitaire du Cancer de Toulouse e Oncopôle, Toulouse, France 3 Department of Biology, Hospices Civils de Lyon, Centre Hospitalier Lyon Sud, Pierre Bénite, France 4 Faculté de Médecine Lyon-Sud Charles Mérieux, Université Claude Bernard Lyon I, Pierre Bénite, France 5 LBMC, ENS, CNRS UMR5239, Faculté de Médecine Lyon-Sud, Pierre Bénite, France
Submitted: May 15, 2018; Revised: Jun 6, 2018; Accepted: Jun 7, 2018; Epub: Jun 13, 2018 Address for correspondence: Etienne Paubelle, MD, PhD, Centre Hospitalier Lyon-Sud, Department of Hematology, Bat.1G, 165 Chemin du Grand Revoyet, 69495 Pierre Bénite, France E-mail contact: [email protected]
2152-2650/$ - see frontmatter ª 2018 Elsevier Inc. All rights reserved. https://doi.org/10.1016/j.clml.2018.06.006
Western countries.1 Over the past decade, considerable advances have been made in the identification of molecular markers leading to the improvement of the risk stratification, especially in patients with AML with normal karyotype.2 However, the prognostic value of most recurrent gene mutations or their combinations remains unclear. An alteration in the FMS-like tyrosine kinase 3 (FLT3) gene can be found in about 30% of AML with a normal karyotype,2 resulting in one of the most affected genes. FLT3 expression is normally restricted to immature hematopoietic progenitor cells, and mediates stem-cell proliferation and survival.3 In AML, mutations of FLT3 lead to a constitutional activation of tyrosine kinases, promoting growth of malignant cells.4 Two mutations have been described: FLT3-ITD for ‘internal tandem duplication’ in or near the juxtamembrane domain of the receptor, and FLT3-TKD, a point mutation in the activation loop of the tyrosine kinase domain (TKD). FLT3-ITD mutation occurs in about 25% of AML, involving
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FLT3-TKD+/NPM1+ in AML. mainly cases with a normal cytogenetic. FLT3-ITD mutation is associated with a poor prognosis. It was shown as an independent predictive factor of relapse and adverse overall survival (OS) except in patients with favorable cytogenetics.5-8 The impact of allelic ratio seems to be crucial. An allelic ratio > 0.5 has been associated with a higher risk of relapse and a shorter OS, whereas patients with an allelic ratio < 0.5 showed a similar outcome than patients without any mutation.9-14 FLT3-TKD mutations occur in about 7% of AML cases. They mainly involve a point mutation in codon D835 or deletions in codon I836.15,16 FLT3-TKD mutations are frequently associated with core binding factor (CBF)-b AML, whereas they seem less frequent in AML with poor cytogenetics.16 Their prognostic value remains unclear. FLT3 mutations have often been described associated with mutations of the nucleophosmin 1 (NPM1) gene, suggesting cooperation in leukemogenesis.17 NPM1 mutations have been associated with chemosensitivity and a favorable outcome.10,18 Despite controversial data, the presence of NPM1 mutation seems to inhibit the pejorative effect of FLT3-ITD,11,18-20 especially when the ITD allelic ratio is low.13 Little is known regarding the association of NPM1 mutations with FLT3-TKD mutations. The main objective of the present retrospective study was to evaluate the prognostic impact of FLT3-TKD in the presence of NPM1 mutation in newly diagnosed patients with AML treated with intensive chemotherapy.
unfavorable-risk cytogenetics. All the other cytogenetic features were classified as intermediate-risk, including normal karyotypes. Screening for mutations in the NPM1 gene, in the CEBPA gene, and in the FLT3-ITD gene was systematically performed. Favorable genotypes were defined as normal karyotype and NPM1 mutation without FLT3-ITD, or FLT3-ITD low allelic ratio (< 0.5), or a biallelic mutated CEBPA. FLT3-ITD was considered as positive, when allelic ratio was above 0.1. Normal karyotypes with NPM1 mutation and with FLT3-ITD high allelic ratio (> 0.5), or NPM1 wild-type (WT) without FLT3-ITD or FLT3-ITD low allelic ratio were classified as intermediate-risk genotypes. NPM1 WT with FLT3-ITD high allelic ratio, RUNX1 mutation, ASXL1 mutation, and TP53 mutation were represented adverse genotypes in accordance with ELN recommendations.22 The identification of RUNX1, ASXL1, and TP53 mutations was performed with nextgeneration sequencing (NGS).
Ethics Statement Written informed consent was obtained from all patients, and all procedures were followed in accordance with the Helsinki declaration as revised in 2008. All data were analyzed anonymously. Each patient was identified with a personal number. Patients were aware that their data were stored in a specific database, and were informed that these data could be used for research purposes. This procedure has been disclosed to the Ethics Committee, which approved it, in accordance with national legislation.
Patients and Methods Study Cohort
Response Criteria and Evaluation
This retrospective study included 126 successive newly diagnosed patients with AML (age 18 years or more) treated with intensive chemotherapy in 2 French centers (Lyon and Toulouse University Hospitals) between 2003 and 2016. Diagnosis of AML was made according to the 2008 World Health Organization (WHO) classification.21 Acute promyelocytic leukemia were excluded.
Response to induction therapy was evaluated on bone marrow (BM) aspirates, performed after peripheral blood cell recovery, or when scheduled by the clinical trial. Remission and progression were defined by international standard criteria.23 CR was defined as < 5% blasts in BM of adequate cellularity, absence of circulating blasts or blasts with Auer rods, absence of extramedullary disease, an absolute neutrophil count greater than or equal to 1 G/L, and platelets of at least 100 G/L with transfusion independency. Hematologic relapse or refractory disease was considered when more than 5% blasts were seen in 2 BM aspirates obtained at a 15-day interval, or in case of blast reappearance in the peripheral blood or occurrence of extramedullary disease.
Treatments All patients received induction consisting of anthracycline and cytarabine “3 þ 7” regimen. Allogeneic stem cell transplantation (SCT) was performed after complete response (CR) achievement if a suitable donor was available in the presence of intermediate or adverse European LeukemiaNet (ELN) risk groups. Patients with favorable-risk AML or those with no donor received between 3cycle consolidation with high-dose cytarabine (AraC) (3 g/m2/12h on days 1, 3, and 5). No patient has received FLT3 inhibitors.
Cytogenetics and Molecular Analysis Cytogenetic data were classified according to standard International System for Human Cytogenetic Nomenclature criteria into favorable-risk, intermediate-risk, or unfavorable-risk subgroups. Karyotype abnormalities that involved chromosome 16 abnormalities [t(16;16), inv(16)], or t(8;21) with or without additional cytogenetic abnormalities were considered favorable cytogenetics. Monosomies and deletions of chromosomes 5 and 7 [-5, -7, del(5) q-, del(7)q-], abnormalities of the long arm of chromosome 3, t(6;9), t(9;22), abnormalities involving the long arm of chromosome 11 (11q23) [except t(9;11)], or complex cytogenetic abnormalities (defined as at least 3 unrelated cytogenetic clones) were considered
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Statistical Analysis The median follow-up was 19.6 months (95% confidence interval [CI], 17-24 months). Descriptive statistics were used to characterize patients and their disease. OS at 3 years was the main endpoint for the study. Survival durations were estimated by the method of Kaplan-Meier and compared by the use of the log-rank test. Hazard ratio (HR) with 95% CI was calculated by the use of the Mantel-Haenszel model. The binary data were compared by using the c2 test and the analysis of variance test, whereas continuous data were compared using the Mann-Whitney test. Multivariate analyses were performed using the Cox proportional hazard model. To evaluate the impact of allogeneic SCT, analyses were performed after censoring or not at the time of transplantation. All analyses were 2-sided, with a P value < .05 considered statistically significant. All analyses were performed using STATA (version 12) and GraphPad Prism (version 5).
Marielle Perry et al Table 1 Characteristics of Patients at the Time of Diagnosis Patients N (%)
WT
FLT3-ITD
FLT3-TKD
ITD þ TKD
82 (65.1)
26 (20.6)
16 (12.7)
2 (1.6)
ALL
P
126 (100)
Patient characteristics Median age, y > 60, n (%) Gender (M/F) Ratio
57.0
59.3
37 (45)
12 (46)
42/40
13/13
50.8
51.8
5 (31.1)
1 (50)
8/8
0/2
57.9
NS
55 (43.7)
NS
63/63
1.05
1
1
0
1
NS
1 (0-120)
40 (0-313)
16 (0-200)
185 (15-355)
10 (0-355)
<10-4
60 (20-90)
80 (40-95)
72 (46-90)
63 (56-95)
70 (20-95)
< 10-4
De novo
44 (58.7)
19 (73.1)
9 (60)
Secondary
6 (40)
Median WBC, G/L (range) Median BM blasts, % (range) AML subtypes, n (%)
NS 28 (37.3)
6 (23.1)
Treatment-related
2 (2.7)
1 (3.9)
Unknown
1 (1.3)
0
0
1 (50) 0 1 (50)
73 (61.9) 40 (33.9) 4 (3.4)
0
0
1 (0.9)
FAB classification, n (%)
NS
AML 0
9 (11)
2 (7,7)
0
0
11 (8.7)
AML 1
19 (23.2)
10 (38.5)
3 (18.8)
0
32 (25.4)
AML 2
15 (18.3)
2 (7.7)
5 (31.3)
1 (50)
23 (18.3)
AML 4
6 (7.32)
5 (19.2)
2 (12.5)
1 (50)
14 (11.1)
AML 5
17 (20.7)
7 (26.9)
6 (37.5)
0
AML 6
3 (3.7)
0
0
0
3 (2.4)
11 (13.4)
0
0
0
11 (8.7)
2 (2.4)
0
0
0
2 (1.6)
Unclassifiable Unknown
30 (23.8)
NPM1 mutations, n (%)
< 10-4
Wild type
64 (78.1)
10 (38,5)
5 (31.3)
2 (100)
81 (64.3)
Muted
18 (21.9)
16 (61.5)
11 (68.7)
0
45 (35.7)
Other mutations, n (%)
NS
RUNX1
16 (19.5)
5 (19.2)
0
22 (17.4)
ASXL1
4 (4.9)
1 (3.8)
1 (6.2) 0
0
4 (3.2)
TP53
6 (7.3)
1 (3.8)
0
0
7 (5.5)
Risk groups according to ELN recommendation, n (%)
NS
Favorable
25 (30.9)
Intermediate
25 (30.9)
17 (65.4)
0
Adverse
31 (38.3)
9 (34.6)
10 (62.5)
0
35 (28)
2 (12.5)
0
44 (35.2)
2 (100)
46 (36.8)
4 (25)
Allogeneic hematopoietic stem cell transplantation, n (%) Number MAC
NS 29 (35.8)
15 (57.7)
7 (41.2)
51 (40.5)
.150
9 (31)
6 (40)
5 (71.4)
0
20 (39.2)
.172
3 (10.3)
2 (13.3)
1 (14.3)
6 (11.8)
HSC source BM PBSC CB
.978 22 (75.9)
12 (80)
5 (71.4)
39 (76.5)
4 (13.8)
1 (6.7)
1 (14.3)
6 (11.8)
Abbreviations: AML ¼ Acute myeloid leukemia; BM ¼ bone marrow; CB ¼ cord blood; ELN ¼ European LeukemiaNet; F ¼ female; HSC ¼ hematopoietic stem cell; ITD ¼ internal tandem duplication; M ¼ male; MAC ¼ myelo-ablative conditioning; NS ¼ not significant; PBSC ¼ peripheral blood stem cell; TKD ¼ tyrosine kinase domain; WBC ¼ white blood cells; WT ¼ wild type.
Results Patient Characteristics One hundred twenty-six patients (median age, 57.9 years; range, 19-74 years) entered the study. The main clinical and biological patient characteristics are summarized in Table 1. Fifty-five patients
(43.7%) were older than 60 years. The male/female gender ratio was 1.0. Seventy-three (61.9%) patients had de novo AML, 40 (33.9%) patients had secondary AML to myelodysplastic syndrome or chronic myeloproliferative disorder, and 4 (3%) patients had treatment-related AML.
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FLT3-TKD+/NPM1+ in AML. Figure 1 Overall Survival in Patients With AML. Kaplan-Meier Representation of Overall Survival Comparing all Patients (A), Patients With Favorable-, Intermediate-, and Unfavorable-Risk AML According to ELN Classification (B), Patients With FLT3-TKD Mutation Versus Patients With FLT3-ITD Mutation, and Patients With FLT3 WT (C), Patients With FLT3-TKD Mutation Versus Patients With FLT3-ITD Mutation, and Patients With FLT3 WT, After Censoring at the Time of Transplant (D)
B
100
Overall survival (%)
Overall survival (%)
A
75 50 25 0
100 75 50 25 0
0
6
12
18
24
30
36
0
6
12
Months
D
100
Overall survival (%)
Overall survival (%)
C
75 50
FLT3 WT FLT3-ITD FLT3-TKD
25
18
24
30
36
24
30
36
Months
0
100 75 50
FLT3 WT FLT3-ITD FLT3-TKD
25 0
0
6
12
18
24
30
36
Months
0
6
12
18
Months
Abbreviations: AML ¼ Acute myeloid leukemia; ELN ¼ European LeukemiaNet; ITD ¼ internal tandem duplication; TKD ¼ tyrosine kinase domain; WT ¼ wild-type.
Twenty-six patients (21%) presented with FLT3-ITD mutation and 16 (13%) with FLT3-TKD mutation, whereas 82 patients (65%) were FLT3 wild type (WT). Two patients were detected with both mutations. Among the FLT3-TKD mutated patients, 12 (63%) patients displayed a D835 mutation. Patients with FLT3 mutations showed a significantly higher median white blood cell count at the time of diagnosis. Median white blood cell count was 40 109/L (range, 0-313 109/L) in FLT3-ITD mutated patients, 16 109/L (range, 0-200 109/L) in the FLT3-TKD patient cohort, versus only 1 109/L (range, 0120 109/L) in the FLT3 WT cohort (P < .0004). The median BM blast percentage was also significantly higher in the FLT3-ITD cohort (80%; range, 40%-95%) and the FLT3-TKD cohort (72%; range, 46%-90%), than in the FLT3 WT cohort (60%; range, 20%-90%) (P < .0004). Clinical and biological features were not significantly different among patient groups defined according to FLT3 status (Table 1). FLT3 mutations were significantly associated with NMP1 mutations. Sixteen patients with FLT3-ITD (61.5%) and 11 patients with FLT3-TKD (68.8%) also displayed NPM1 mutations, whereas only 18 patients (21.9%) with FLT3 WT showed a NPM1 mutation (P < .0004). There were no significant differences among patient subgroups regarding the type of induction treatment.
Treatment Outcome CR rates after induction chemotherapy did not significantly differ among patient subgroups defined according to FLT3 status. After 1
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course of chemotherapy, 76.9% (95% CI, 56.4%-91%) of patients in the FLT3-ITDþ subgroup achieved CR, 81.2% (95% CI, 54.3%-95.9%) in the FLT3-TKDþ subgroup, and 71.9% (95% CI, 61.9%-81.3%) in FLT3 WT patients (P ¼ .69). Refractory patients after a second course of induction chemotherapy represented 19.2% (95% CI, 6.6%-39.4%) in the FLT3-ITDþ subgroup versus 6.3% (95% CI, 0.1%-30.2%) in the FLT3-TKDþ subgroup, and 11% (95% CI, 5.1%-19.8%) in FLT3 WT patients (P ¼ .40). After CR achievement, 52 patients (41%) received allogeneic SCT according to the ELN recommendations.22 Twenty-three patients (44%) received myeloablative conditioning regimen, whereas 26 patients (54%) received reduced intensity conditioning regimen. The stem cell source was peripheral blood in 40 patients (76%), BM in 6 patients (12%), and umbilical cord blood in 6 patients (12%). Seventeen patients (37.7%) had a human leukocyte antigen sibling donor, and 28 (62.3%) had a matched unrelated donor. The mean duration from initial diagnosis to SCT was 112 days. The median overall survival of the entire cohort was not reached, with a 2-year OS rate of 58.2% (95% CI, 48.6%-66.6%) (Figure 1A). In order to evaluate the effect of allogeneic SCT, analyses were also performed after censoring at the time of the transplant. There were no significant differences between analyses when censoring or not at the time of transplant. Patients with unfavorable-risk AML had a median OS of 14.2 months (95% CI, 9.4-25.9 months), whereas the median was not reached in patients with intermediate- or favorable-risk AML (P < 10-4) (Figure 1B). The median OS was not reached in FLT3-TKDþ patients, 18.8
Marielle Perry et al Figure 2 Overall Survival in Patients With AML According to NPM1 Status and FLT3-TKD Status. Kaplan-Meier Representation of Overall Survival Comparing NPM1 WT and NPM1 mutated Patients (A), FLT3-TKDD/NPM1D Patients Compared With the Other Patients (B), FLT3-TKDD/NPM1D Patients Compared With the Others Patients after Censoring at the Time of Transplant (C)
B
100 75 50 25
NPM1 WT NPM1 mutated
0 0
Overall survival (%)
C
6
12
18
100
Overall survival (%)
Overall survival (%)
A
75
p=0.04
50
p=0.25
FLT3-TKD, mutated NPM1 NMP1 + FLT3-TKD negative others
25 0
24
30
36
p=0.01
0
6
Months
12
18
24
30
36
Months
100 75
p=0.25 p=0.05
50
p=0.12
FLT3-TKD, mutated NPM1 NMP1 + FLT3-TKD negative others
25 0 0
6
12
18
24
30
36
Months
Abbreviations: AML ¼ Acute myeloid leukemia; TKD ¼ tyrosine kinase domain; WT ¼ wild-type.
months in FLT3-ITDþ, and 30.9 months in FLT3-WT patients (Figure 1C). When censoring at the time of transplant, median OS was not reached in FLT3-TKDþ patients, 14.2 months in FLT3-ITDþ patients, and 33.7 months in FLT3-WT patients (Figure 1D).
Combination of FLT3-TKD and NPM1 Mutations The median OS in NPM1 mutated patients was not reached versus 25.9 months in NPM1-WT patients with an HR of 1.89 (95% CI, 1.10-3.24; P ¼ .02) (Figure 2A). The median OS in FLT3-TKDþ/NPM1þ mutated patients was not reached versus 30.9 months in the other patients, with a HR of 0.32 (95% CI, 0.14-0.73; P < .01) (Figure 2B).When censoring at the time of transplantation, median OS in FLT3-TKDþ/NPM1þ mutated patients was not reached versus 31 months in the other patients with a HR of 0.32 (95% CI, 0.11-0.91; P ¼ .03) (Figure 2C). In order to investigate the prognostic value of the
FLT3-TKDþ/NPM1þ genotype, a multivariate analysis was performed with a model including the cytogenetic data, FLT3-ITD status, and NPM1 status with or without FLT3-TKD. Results are summarized in Table 2. Cytogenetic group and FLT3-ITD status were highly significantly associated with outcome regardless of allograft censoring. NPM1þ-FLT3-TKDþ was also associated with outcome, whereas NPM1þ-FLT3-TKD- was not (Table 2).
Discussion Advances have been made over the past decade in deciphering risk groups in adult AML. Cytogenetic classifications have been enriched by molecular marker analyses,22 and these determinants are currently used for treatment decision-making, especially regarding allogeneic SCT as consolidation therapy. Among the most tested molecular markers, NPM1 gene mutations are detected in approximately one-third of all cases of AML, involving up to 60% of patients with AML with a normal karyotype.10 NPM1 mutations
Table 2 Multivariate Analysis Non-censoring at the Time of Transplant
Censoring at the Time of Transplant
Factors
HR
95% CI
P
HR
95% CI
P
Cytogenetic group FLT3-ITD NPM1 mutated without FLT3-TKD NPM1 mutated with FLT3-TKD
0.51 2.31 2.00 0.38
0.32-0.81 1.17-4.57 0.70-5.71 0.18-0.81
.004 .016 .195 .012
0.46 7.85 2.30 0.22
0.26-0.82 2.71-22.72 0.55-9.66 0.07-0.68
.008 < .001 .252 .009
Abbreviations: CI ¼ confidence interval; HR ¼ hazard ratio; ITD ¼ internal tandem duplication; NS ¼ not significant; TKD ¼ tyrosine kinase domain.
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FLT3-TKD+/NPM1+ in AML. are generally considered of favorable outcome. Reversely, FLT3ITD mutation which is found in about 30% of cases of AML with normal karyotype2 is associated with an unfavorable prognosis. However, the impact of other mutations remains unclear. This is the case of FLT3-TKD mutation, for which prior analyses showed controversial results.15,16,21,24 The present retrospective study aimed at evaluating the prognosis impact of FLT3-TKD mutations in newly diagnosed adult patients with AML receiving a front-line therapy. Regarding NPM1 and FLT3-ITD status, our results confirmed prior published data.5,7,11,13,18 Although the incidence of FLT3-TKD mutations was much higher in our series (14.9%) than in a previous large published series (4.8%),21 our results confirmed that FLT3-TKDþ/NPM1þ patients defined a favorable group of patients. These results stress on the importance of determining FLT3-TKD status at diagnosis and question about how to consider the prognostic value of NPM1 mutations in the absence of information regarding FLT3-TKD status. With regard to these results, allogeneic SCT might not be considered after first CR achievement in this patient population and should be reserved only in second-line therapy. Boddu et al recently showed, in a cohort of 1319 patients, that co-occurrence of FLT3-TKD and NPM1 mutations defines a highly favorable prognostic AML group.25 The main limitation of our study was the small size of our series. We therefore did not have means to properly assess prognosis among the different types of FLT3-TKD mutations. However, our results reproduce those of the Boddu et al cohort, indicating the interest of the prognostic value of the double mutation. In conclusion, FLT3-TKD mutations should be systematically determined at the time of initial diagnosis in patients with AML. The favorable prognostic value in patients with both FLT3-TKD and NPM1 mutations, if confirmed in larger studies, could be integrated in the prognostic classification of AML. Although allogeneic SCT represents a standard of care for consolidating patients with FLT3-ITD AML in first CR, FLT3-TKDþ/NPM1þ patients appear as not candidates for transplantation in first-line therapy. Patients should benefit from the combination of TKI with induction and consolidation chemotherapy, and potentially for maintenance therapy over MRD monitoring determined by NPM1 molecular biology.
Clinical Practice Points The outcome of patients with mutation of the FLT3-TKD in
AML remains controversial. We present a retrospective study of 126 newly diagnosed patients
with AML. Our data suggest that FLT3-TKD mutations should be routinely determined at the time of diagnosis. FLT3-TKD in association with NPM1 mutations define a favorable-risk group in patients with AML. Better defining prognostic groups should better guide treatment in the future. Patients with favorable risk may not be offered allogeneic hematopoietic stem cell transplantation in first intention, especially when targeted therapies directed against FLT3 are emerging.
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Disclosure The authors have stated that they have no conflicts of interest.
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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; 98:1752-9. 7. Schlenk RF, Dohner K, Krauter J, et al. Mutations and treatment outcome in cytogenetically normal acute myeloid leukemia. N Engl J Med 2008; 358:1909-18. 8. Yanada M, Matsuo K, Suzuki T, Kiyoi H, Naoe T. Prognostic significance of FLT3 internal tandem duplication and tyrosine kinase domain mutations for acute myeloid leukemia: a meta-analysis. Leukemia 2005; 19:1345-9. 9. 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; 99:4326-35. 10. Falini B, Mecucci C, Tiacci E, et al. Cytoplasmic nucleophosmin in acute myelogenous leukemia with a normal karyotype. N Eng J Med 2005; 352:254-66. 11. 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; 111:2776-84. 12. Green C, Linch DC, Gale RE. Most acute myeloid leukaemia patients with intermediate mutant FLT3/ITD levels do not have detectable bi-allelic disease, indicating that heterozygous disease alone is associated with an adverse outcome. Br J Haematol 2008; 142:423-6. 13. Pratcorona M, Brunet S, Nomdedeu J, et al. Favorable outcome of patients with acute myeloid leukemia harboring a low-allelic burden FLT3-ITD mutation and concomitant NPM1 mutation: relevance to post-remission therapy. Blood 2013; 121:2734-8. 14. Kim Y, Lee GD, Park J, et al. Quantitative fragment analysis of FLT3-ITD efficiently identifying poor prognostic group with high mutant allele burden or long ITD length. Blood Cancer J 2015; 5:e336. 15. 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: 2434-9. 16. Mead AJ, Linch DC, Hills RK, Wheatley K, Burnett AK, Gale RE. 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; 110:1262-70. 17. Mupo A, Celani L, Dovey O, et al. A powerful molecular synergy between mutant Nucleophosmin and Flt3-ITD drives acute myeloid leukemia in mice. Leukemia 2013; 27:1917-20. 18. Falini B, Nicoletti I, Martelli MF, Mecucci C. Acute myeloid leukemia carrying cytoplasmic/mutated nucleophosmin (NPMcþ AML): biologic and clinical features. Blood 2007; 109:874-85. 19. Schlenk RF, Kayser S, Bullinger L, et al. Differential impact of allelic ratio and insertion site in FLT3-ITD-positive AML with respect to allogeneic transplantation. Blood 2014; 124:3441-9. 20. Schmid C, Labopin M, Socie G, et al. Outcome of patients with distinct molecular genotypes and cytogenetically normal AML after allogeneic transplantation. Blood 2015; 126:2062-9. 21. Bacher U, Haferlach C, Kern W, Haferlach T, Schnittger S. Prognostic relevance of FLT3-TKD mutations in AML: the combination mattersean analysis of 3082 patients. Blood 2008; 111:2527-37. 22. Dohner H, Estey E, Grimwade D, et al. Diagnosis and management of AML in adults: 2017 ELN recommendations from an international expert panel. Blood 2017; 129:424-47. 23. Cheson BD, Bennett JM, Kopecky KJ, et al. Revised recommendations of the International Working Group for Diagnosis, Standardization of Response Criteria, Treatment Outcomes, and Reporting Standards for Therapeutic Trials in Acute Myeloid Leukemia. J Clin Oncol 2003; 21:4642-9. 24. 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 duplications. Blood 2008; 111:1552-9. 25. Boddu P, Kantarjian H, Borthakur G, et al. Co-occurrence of FLT3-TKD and NPM1 mutations defines a highly favorable prognostic AML group. Blood Adv 2017; 1:1546-50.
FLT3-TKD Mutations Associated With NPM1 Mutations Define a Favorable-risk Group in Patients With Acute Myeloid Leukemia Marielle Perry,1 Sarah Bertoli,2 Clément Rocher,1 Sandrine Hayette,3 Sophie Ducastelle,1 Fiorenza Barraco,1 Hélène Labussière-Wallet,1 Gilles Salles,1,4 Christian Recher,2 Xavier Thomas,1 Etienne Paubelle1,4,5 Abstract The outcome of patients with mutation of the FLT3 tyrosine kinase domain (FLT3-TKD) in acute myeloid leukemia (AML) remains controversial. We present a retrospective study of 126 newly diagnosed patients with AML. Our data suggest that FLT3-TKD mutations should be routinely determined at the time of diagnosis. FLT3-TKD in association with NPM1 mutations define a favorable-risk group in patients with AML. Background: Outcome of patients with mutation of the FLT3 tyrosine kinase domain (FLT3-TKD) in acute myeloid leukemia (AML) remains controversial. Patients and Methods: Herein, we present a retrospective study of 126 newly diagnosed patients with AML performed in 2 French centers. Results: FLT3-TKD mutations represented 12.7% of patients, whereas FLT3-internal tandem duplication (ITD) mutation was observed in 20.6% of AML cases and 1.6% of patients harbored both anomalies. At diagnosis, FLT3-TKD and FLT3-ITD were associated with higher peripheral leukocytes count and a higher blast count in bone marrow (P < 10-4). Mutations of the NPM1 gene were frequently associated to FLT3-TKD (68.7%) and FLT3-ITD (61.5%) mutations compared with FLT3 wild type (WT) patients (P < 10-4). Patients with both FLT3-TKD and NPM1 mutations (n ¼ 12; 9.5%) showed a favorable outcome. Interestingly, mutations in NPM1 gene lost their favorable prognostic when not associated with FLT3-TKD both in univariate and multivariate analyses. Conclusion: Our data suggest that FLT3-TKD mutations should be routinely determined at the time of diagnosis. In association with NPM1 mutations, patients should follow the therapeutic schedule of favorable-risk patients with AML. Clinical Lymphoma, Myeloma & Leukemia, Vol. 18, No. 12, e545-50 ª 2018 Elsevier Inc. All rights reserved. Keywords: Chemotherapy, Favorable risk-group, FLT3-ITD mutation, Prognosis
Introduction Acute myeloid leukemia (AML) is an aggressive malignant disease affecting 2.5 to 3.5 per 100,000 adults each year in the 1 Department of Hematology, Hospices Civils de Lyon, Centre Hospitalier Lyon Sud, Pierre-Bénite, France 2 Department of Hematology, Institut Universitaire du Cancer de Toulouse e Oncopôle, Toulouse, France 3 Department of Biology, Hospices Civils de Lyon, Centre Hospitalier Lyon Sud, Pierre Bénite, France 4 Faculté de Médecine Lyon-Sud Charles Mérieux, Université Claude Bernard Lyon I, Pierre Bénite, France 5 LBMC, ENS, CNRS UMR5239, Faculté de Médecine Lyon-Sud, Pierre Bénite, France
Submitted: May 15, 2018; Revised: Jun 6, 2018; Accepted: Jun 7, 2018; Epub: Jun 13, 2018 Address for correspondence: Etienne Paubelle, MD, PhD, Centre Hospitalier Lyon-Sud, Department of Hematology, Bat.1G, 165 Chemin du Grand Revoyet, 69495 Pierre Bénite, France E-mail contact: [email protected]
2152-2650/$ - see frontmatter ª 2018 Elsevier Inc. All rights reserved. https://doi.org/10.1016/j.clml.2018.06.006
Western countries.1 Over the past decade, considerable advances have been made in the identification of molecular markers leading to the improvement of the risk stratification, especially in patients with AML with normal karyotype.2 However, the prognostic value of most recurrent gene mutations or their combinations remains unclear. An alteration in the FMS-like tyrosine kinase 3 (FLT3) gene can be found in about 30% of AML with a normal karyotype,2 resulting in one of the most affected genes. FLT3 expression is normally restricted to immature hematopoietic progenitor cells, and mediates stem-cell proliferation and survival.3 In AML, mutations of FLT3 lead to a constitutional activation of tyrosine kinases, promoting growth of malignant cells.4 Two mutations have been described: FLT3-ITD for ‘internal tandem duplication’ in or near the juxtamembrane domain of the receptor, and FLT3-TKD, a point mutation in the activation loop of the tyrosine kinase domain (TKD). FLT3-ITD mutation occurs in about 25% of AML, involving
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FLT3-TKD+/NPM1+ in AML. mainly cases with a normal cytogenetic. FLT3-ITD mutation is associated with a poor prognosis. It was shown as an independent predictive factor of relapse and adverse overall survival (OS) except in patients with favorable cytogenetics.5-8 The impact of allelic ratio seems to be crucial. An allelic ratio > 0.5 has been associated with a higher risk of relapse and a shorter OS, whereas patients with an allelic ratio < 0.5 showed a similar outcome than patients without any mutation.9-14 FLT3-TKD mutations occur in about 7% of AML cases. They mainly involve a point mutation in codon D835 or deletions in codon I836.15,16 FLT3-TKD mutations are frequently associated with core binding factor (CBF)-b AML, whereas they seem less frequent in AML with poor cytogenetics.16 Their prognostic value remains unclear. FLT3 mutations have often been described associated with mutations of the nucleophosmin 1 (NPM1) gene, suggesting cooperation in leukemogenesis.17 NPM1 mutations have been associated with chemosensitivity and a favorable outcome.10,18 Despite controversial data, the presence of NPM1 mutation seems to inhibit the pejorative effect of FLT3-ITD,11,18-20 especially when the ITD allelic ratio is low.13 Little is known regarding the association of NPM1 mutations with FLT3-TKD mutations. The main objective of the present retrospective study was to evaluate the prognostic impact of FLT3-TKD in the presence of NPM1 mutation in newly diagnosed patients with AML treated with intensive chemotherapy.
unfavorable-risk cytogenetics. All the other cytogenetic features were classified as intermediate-risk, including normal karyotypes. Screening for mutations in the NPM1 gene, in the CEBPA gene, and in the FLT3-ITD gene was systematically performed. Favorable genotypes were defined as normal karyotype and NPM1 mutation without FLT3-ITD, or FLT3-ITD low allelic ratio (< 0.5), or a biallelic mutated CEBPA. FLT3-ITD was considered as positive, when allelic ratio was above 0.1. Normal karyotypes with NPM1 mutation and with FLT3-ITD high allelic ratio (> 0.5), or NPM1 wild-type (WT) without FLT3-ITD or FLT3-ITD low allelic ratio were classified as intermediate-risk genotypes. NPM1 WT with FLT3-ITD high allelic ratio, RUNX1 mutation, ASXL1 mutation, and TP53 mutation were represented adverse genotypes in accordance with ELN recommendations.22 The identification of RUNX1, ASXL1, and TP53 mutations was performed with nextgeneration sequencing (NGS).
Ethics Statement Written informed consent was obtained from all patients, and all procedures were followed in accordance with the Helsinki declaration as revised in 2008. All data were analyzed anonymously. Each patient was identified with a personal number. Patients were aware that their data were stored in a specific database, and were informed that these data could be used for research purposes. This procedure has been disclosed to the Ethics Committee, which approved it, in accordance with national legislation.
Patients and Methods Study Cohort
Response Criteria and Evaluation
This retrospective study included 126 successive newly diagnosed patients with AML (age 18 years or more) treated with intensive chemotherapy in 2 French centers (Lyon and Toulouse University Hospitals) between 2003 and 2016. Diagnosis of AML was made according to the 2008 World Health Organization (WHO) classification.21 Acute promyelocytic leukemia were excluded.
Response to induction therapy was evaluated on bone marrow (BM) aspirates, performed after peripheral blood cell recovery, or when scheduled by the clinical trial. Remission and progression were defined by international standard criteria.23 CR was defined as < 5% blasts in BM of adequate cellularity, absence of circulating blasts or blasts with Auer rods, absence of extramedullary disease, an absolute neutrophil count greater than or equal to 1 G/L, and platelets of at least 100 G/L with transfusion independency. Hematologic relapse or refractory disease was considered when more than 5% blasts were seen in 2 BM aspirates obtained at a 15-day interval, or in case of blast reappearance in the peripheral blood or occurrence of extramedullary disease.
Treatments All patients received induction consisting of anthracycline and cytarabine “3 þ 7” regimen. Allogeneic stem cell transplantation (SCT) was performed after complete response (CR) achievement if a suitable donor was available in the presence of intermediate or adverse European LeukemiaNet (ELN) risk groups. Patients with favorable-risk AML or those with no donor received between 3cycle consolidation with high-dose cytarabine (AraC) (3 g/m2/12h on days 1, 3, and 5). No patient has received FLT3 inhibitors.
Cytogenetics and Molecular Analysis Cytogenetic data were classified according to standard International System for Human Cytogenetic Nomenclature criteria into favorable-risk, intermediate-risk, or unfavorable-risk subgroups. Karyotype abnormalities that involved chromosome 16 abnormalities [t(16;16), inv(16)], or t(8;21) with or without additional cytogenetic abnormalities were considered favorable cytogenetics. Monosomies and deletions of chromosomes 5 and 7 [-5, -7, del(5) q-, del(7)q-], abnormalities of the long arm of chromosome 3, t(6;9), t(9;22), abnormalities involving the long arm of chromosome 11 (11q23) [except t(9;11)], or complex cytogenetic abnormalities (defined as at least 3 unrelated cytogenetic clones) were considered
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Statistical Analysis The median follow-up was 19.6 months (95% confidence interval [CI], 17-24 months). Descriptive statistics were used to characterize patients and their disease. OS at 3 years was the main endpoint for the study. Survival durations were estimated by the method of Kaplan-Meier and compared by the use of the log-rank test. Hazard ratio (HR) with 95% CI was calculated by the use of the Mantel-Haenszel model. The binary data were compared by using the c2 test and the analysis of variance test, whereas continuous data were compared using the Mann-Whitney test. Multivariate analyses were performed using the Cox proportional hazard model. To evaluate the impact of allogeneic SCT, analyses were performed after censoring or not at the time of transplantation. All analyses were 2-sided, with a P value < .05 considered statistically significant. All analyses were performed using STATA (version 12) and GraphPad Prism (version 5).
Marielle Perry et al Table 1 Characteristics of Patients at the Time of Diagnosis Patients N (%)
WT
FLT3-ITD
FLT3-TKD
ITD þ TKD
82 (65.1)
26 (20.6)
16 (12.7)
2 (1.6)
ALL
P
126 (100)
Patient characteristics Median age, y > 60, n (%) Gender (M/F) Ratio
57.0
59.3
37 (45)
12 (46)
42/40
13/13
50.8
51.8
5 (31.1)
1 (50)
8/8
0/2
57.9
NS
55 (43.7)
NS
63/63
1.05
1
1
0
1
NS
1 (0-120)
40 (0-313)
16 (0-200)
185 (15-355)
10 (0-355)
<10-4
60 (20-90)
80 (40-95)
72 (46-90)
63 (56-95)
70 (20-95)
< 10-4
De novo
44 (58.7)
19 (73.1)
9 (60)
Secondary
6 (40)
Median WBC, G/L (range) Median BM blasts, % (range) AML subtypes, n (%)
NS 28 (37.3)
6 (23.1)
Treatment-related
2 (2.7)
1 (3.9)
Unknown
1 (1.3)
0
0
1 (50) 0 1 (50)
73 (61.9) 40 (33.9) 4 (3.4)
0
0
1 (0.9)
FAB classification, n (%)
NS
AML 0
9 (11)
2 (7,7)
0
0
11 (8.7)
AML 1
19 (23.2)
10 (38.5)
3 (18.8)
0
32 (25.4)
AML 2
15 (18.3)
2 (7.7)
5 (31.3)
1 (50)
23 (18.3)
AML 4
6 (7.32)
5 (19.2)
2 (12.5)
1 (50)
14 (11.1)
AML 5
17 (20.7)
7 (26.9)
6 (37.5)
0
AML 6
3 (3.7)
0
0
0
3 (2.4)
11 (13.4)
0
0
0
11 (8.7)
2 (2.4)
0
0
0
2 (1.6)
Unclassifiable Unknown
30 (23.8)
NPM1 mutations, n (%)
< 10-4
Wild type
64 (78.1)
10 (38,5)
5 (31.3)
2 (100)
81 (64.3)
Muted
18 (21.9)
16 (61.5)
11 (68.7)
0
45 (35.7)
Other mutations, n (%)
NS
RUNX1
16 (19.5)
5 (19.2)
0
22 (17.4)
ASXL1
4 (4.9)
1 (3.8)
1 (6.2) 0
0
4 (3.2)
TP53
6 (7.3)
1 (3.8)
0
0
7 (5.5)
Risk groups according to ELN recommendation, n (%)
NS
Favorable
25 (30.9)
Intermediate
25 (30.9)
17 (65.4)
0
Adverse
31 (38.3)
9 (34.6)
10 (62.5)
0
35 (28)
2 (12.5)
0
44 (35.2)
2 (100)
46 (36.8)
4 (25)
Allogeneic hematopoietic stem cell transplantation, n (%) Number MAC
NS 29 (35.8)
15 (57.7)
7 (41.2)
51 (40.5)
.150
9 (31)
6 (40)
5 (71.4)
0
20 (39.2)
.172
3 (10.3)
2 (13.3)
1 (14.3)
6 (11.8)
HSC source BM PBSC CB
.978 22 (75.9)
12 (80)
5 (71.4)
39 (76.5)
4 (13.8)
1 (6.7)
1 (14.3)
6 (11.8)
Abbreviations: AML ¼ Acute myeloid leukemia; BM ¼ bone marrow; CB ¼ cord blood; ELN ¼ European LeukemiaNet; F ¼ female; HSC ¼ hematopoietic stem cell; ITD ¼ internal tandem duplication; M ¼ male; MAC ¼ myelo-ablative conditioning; NS ¼ not significant; PBSC ¼ peripheral blood stem cell; TKD ¼ tyrosine kinase domain; WBC ¼ white blood cells; WT ¼ wild type.
Results Patient Characteristics One hundred twenty-six patients (median age, 57.9 years; range, 19-74 years) entered the study. The main clinical and biological patient characteristics are summarized in Table 1. Fifty-five patients
(43.7%) were older than 60 years. The male/female gender ratio was 1.0. Seventy-three (61.9%) patients had de novo AML, 40 (33.9%) patients had secondary AML to myelodysplastic syndrome or chronic myeloproliferative disorder, and 4 (3%) patients had treatment-related AML.
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FLT3-TKD+/NPM1+ in AML. Figure 1 Overall Survival in Patients With AML. Kaplan-Meier Representation of Overall Survival Comparing all Patients (A), Patients With Favorable-, Intermediate-, and Unfavorable-Risk AML According to ELN Classification (B), Patients With FLT3-TKD Mutation Versus Patients With FLT3-ITD Mutation, and Patients With FLT3 WT (C), Patients With FLT3-TKD Mutation Versus Patients With FLT3-ITD Mutation, and Patients With FLT3 WT, After Censoring at the Time of Transplant (D)
B
100
Overall survival (%)
Overall survival (%)
A
75 50 25 0
100 75 50 25 0
0
6
12
18
24
30
36
0
6
12
Months
D
100
Overall survival (%)
Overall survival (%)
C
75 50
FLT3 WT FLT3-ITD FLT3-TKD
25
18
24
30
36
24
30
36
Months
0
100 75 50
FLT3 WT FLT3-ITD FLT3-TKD
25 0
0
6
12
18
24
30
36
Months
0
6
12
18
Months
Abbreviations: AML ¼ Acute myeloid leukemia; ELN ¼ European LeukemiaNet; ITD ¼ internal tandem duplication; TKD ¼ tyrosine kinase domain; WT ¼ wild-type.
Twenty-six patients (21%) presented with FLT3-ITD mutation and 16 (13%) with FLT3-TKD mutation, whereas 82 patients (65%) were FLT3 wild type (WT). Two patients were detected with both mutations. Among the FLT3-TKD mutated patients, 12 (63%) patients displayed a D835 mutation. Patients with FLT3 mutations showed a significantly higher median white blood cell count at the time of diagnosis. Median white blood cell count was 40 109/L (range, 0-313 109/L) in FLT3-ITD mutated patients, 16 109/L (range, 0-200 109/L) in the FLT3-TKD patient cohort, versus only 1 109/L (range, 0120 109/L) in the FLT3 WT cohort (P < .0004). The median BM blast percentage was also significantly higher in the FLT3-ITD cohort (80%; range, 40%-95%) and the FLT3-TKD cohort (72%; range, 46%-90%), than in the FLT3 WT cohort (60%; range, 20%-90%) (P < .0004). Clinical and biological features were not significantly different among patient groups defined according to FLT3 status (Table 1). FLT3 mutations were significantly associated with NMP1 mutations. Sixteen patients with FLT3-ITD (61.5%) and 11 patients with FLT3-TKD (68.8%) also displayed NPM1 mutations, whereas only 18 patients (21.9%) with FLT3 WT showed a NPM1 mutation (P < .0004). There were no significant differences among patient subgroups regarding the type of induction treatment.
Treatment Outcome CR rates after induction chemotherapy did not significantly differ among patient subgroups defined according to FLT3 status. After 1
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course of chemotherapy, 76.9% (95% CI, 56.4%-91%) of patients in the FLT3-ITDþ subgroup achieved CR, 81.2% (95% CI, 54.3%-95.9%) in the FLT3-TKDþ subgroup, and 71.9% (95% CI, 61.9%-81.3%) in FLT3 WT patients (P ¼ .69). Refractory patients after a second course of induction chemotherapy represented 19.2% (95% CI, 6.6%-39.4%) in the FLT3-ITDþ subgroup versus 6.3% (95% CI, 0.1%-30.2%) in the FLT3-TKDþ subgroup, and 11% (95% CI, 5.1%-19.8%) in FLT3 WT patients (P ¼ .40). After CR achievement, 52 patients (41%) received allogeneic SCT according to the ELN recommendations.22 Twenty-three patients (44%) received myeloablative conditioning regimen, whereas 26 patients (54%) received reduced intensity conditioning regimen. The stem cell source was peripheral blood in 40 patients (76%), BM in 6 patients (12%), and umbilical cord blood in 6 patients (12%). Seventeen patients (37.7%) had a human leukocyte antigen sibling donor, and 28 (62.3%) had a matched unrelated donor. The mean duration from initial diagnosis to SCT was 112 days. The median overall survival of the entire cohort was not reached, with a 2-year OS rate of 58.2% (95% CI, 48.6%-66.6%) (Figure 1A). In order to evaluate the effect of allogeneic SCT, analyses were also performed after censoring at the time of the transplant. There were no significant differences between analyses when censoring or not at the time of transplant. Patients with unfavorable-risk AML had a median OS of 14.2 months (95% CI, 9.4-25.9 months), whereas the median was not reached in patients with intermediate- or favorable-risk AML (P < 10-4) (Figure 1B). The median OS was not reached in FLT3-TKDþ patients, 18.8
Marielle Perry et al Figure 2 Overall Survival in Patients With AML According to NPM1 Status and FLT3-TKD Status. Kaplan-Meier Representation of Overall Survival Comparing NPM1 WT and NPM1 mutated Patients (A), FLT3-TKDD/NPM1D Patients Compared With the Other Patients (B), FLT3-TKDD/NPM1D Patients Compared With the Others Patients after Censoring at the Time of Transplant (C)
B
100 75 50 25
NPM1 WT NPM1 mutated
0 0
Overall survival (%)
C
6
12
18
100
Overall survival (%)
Overall survival (%)
A
75
p=0.04
50
p=0.25
FLT3-TKD, mutated NPM1 NMP1 + FLT3-TKD negative others
25 0
24
30
36
p=0.01
0
6
Months
12
18
24
30
36
Months
100 75
p=0.25 p=0.05
50
p=0.12
FLT3-TKD, mutated NPM1 NMP1 + FLT3-TKD negative others
25 0 0
6
12
18
24
30
36
Months
Abbreviations: AML ¼ Acute myeloid leukemia; TKD ¼ tyrosine kinase domain; WT ¼ wild-type.
months in FLT3-ITDþ, and 30.9 months in FLT3-WT patients (Figure 1C). When censoring at the time of transplant, median OS was not reached in FLT3-TKDþ patients, 14.2 months in FLT3-ITDþ patients, and 33.7 months in FLT3-WT patients (Figure 1D).
Combination of FLT3-TKD and NPM1 Mutations The median OS in NPM1 mutated patients was not reached versus 25.9 months in NPM1-WT patients with an HR of 1.89 (95% CI, 1.10-3.24; P ¼ .02) (Figure 2A). The median OS in FLT3-TKDþ/NPM1þ mutated patients was not reached versus 30.9 months in the other patients, with a HR of 0.32 (95% CI, 0.14-0.73; P < .01) (Figure 2B).When censoring at the time of transplantation, median OS in FLT3-TKDþ/NPM1þ mutated patients was not reached versus 31 months in the other patients with a HR of 0.32 (95% CI, 0.11-0.91; P ¼ .03) (Figure 2C). In order to investigate the prognostic value of the
FLT3-TKDþ/NPM1þ genotype, a multivariate analysis was performed with a model including the cytogenetic data, FLT3-ITD status, and NPM1 status with or without FLT3-TKD. Results are summarized in Table 2. Cytogenetic group and FLT3-ITD status were highly significantly associated with outcome regardless of allograft censoring. NPM1þ-FLT3-TKDþ was also associated with outcome, whereas NPM1þ-FLT3-TKD- was not (Table 2).
Discussion Advances have been made over the past decade in deciphering risk groups in adult AML. Cytogenetic classifications have been enriched by molecular marker analyses,22 and these determinants are currently used for treatment decision-making, especially regarding allogeneic SCT as consolidation therapy. Among the most tested molecular markers, NPM1 gene mutations are detected in approximately one-third of all cases of AML, involving up to 60% of patients with AML with a normal karyotype.10 NPM1 mutations
Table 2 Multivariate Analysis Non-censoring at the Time of Transplant
Censoring at the Time of Transplant
Factors
HR
95% CI
P
HR
95% CI
P
Cytogenetic group FLT3-ITD NPM1 mutated without FLT3-TKD NPM1 mutated with FLT3-TKD
0.51 2.31 2.00 0.38
0.32-0.81 1.17-4.57 0.70-5.71 0.18-0.81
.004 .016 .195 .012
0.46 7.85 2.30 0.22
0.26-0.82 2.71-22.72 0.55-9.66 0.07-0.68
.008 < .001 .252 .009
Abbreviations: CI ¼ confidence interval; HR ¼ hazard ratio; ITD ¼ internal tandem duplication; NS ¼ not significant; TKD ¼ tyrosine kinase domain.
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FLT3-TKD+/NPM1+ in AML. are generally considered of favorable outcome. Reversely, FLT3ITD mutation which is found in about 30% of cases of AML with normal karyotype2 is associated with an unfavorable prognosis. However, the impact of other mutations remains unclear. This is the case of FLT3-TKD mutation, for which prior analyses showed controversial results.15,16,21,24 The present retrospective study aimed at evaluating the prognosis impact of FLT3-TKD mutations in newly diagnosed adult patients with AML receiving a front-line therapy. Regarding NPM1 and FLT3-ITD status, our results confirmed prior published data.5,7,11,13,18 Although the incidence of FLT3-TKD mutations was much higher in our series (14.9%) than in a previous large published series (4.8%),21 our results confirmed that FLT3-TKDþ/NPM1þ patients defined a favorable group of patients. These results stress on the importance of determining FLT3-TKD status at diagnosis and question about how to consider the prognostic value of NPM1 mutations in the absence of information regarding FLT3-TKD status. With regard to these results, allogeneic SCT might not be considered after first CR achievement in this patient population and should be reserved only in second-line therapy. Boddu et al recently showed, in a cohort of 1319 patients, that co-occurrence of FLT3-TKD and NPM1 mutations defines a highly favorable prognostic AML group.25 The main limitation of our study was the small size of our series. We therefore did not have means to properly assess prognosis among the different types of FLT3-TKD mutations. However, our results reproduce those of the Boddu et al cohort, indicating the interest of the prognostic value of the double mutation. In conclusion, FLT3-TKD mutations should be systematically determined at the time of initial diagnosis in patients with AML. The favorable prognostic value in patients with both FLT3-TKD and NPM1 mutations, if confirmed in larger studies, could be integrated in the prognostic classification of AML. Although allogeneic SCT represents a standard of care for consolidating patients with FLT3-ITD AML in first CR, FLT3-TKDþ/NPM1þ patients appear as not candidates for transplantation in first-line therapy. Patients should benefit from the combination of TKI with induction and consolidation chemotherapy, and potentially for maintenance therapy over MRD monitoring determined by NPM1 molecular biology.
Clinical Practice Points The outcome of patients with mutation of the FLT3-TKD in
AML remains controversial. We present a retrospective study of 126 newly diagnosed patients
with AML. Our data suggest that FLT3-TKD mutations should be routinely determined at the time of diagnosis. FLT3-TKD in association with NPM1 mutations define a favorable-risk group in patients with AML. Better defining prognostic groups should better guide treatment in the future. Patients with favorable risk may not be offered allogeneic hematopoietic stem cell transplantation in first intention, especially when targeted therapies directed against FLT3 are emerging.
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Disclosure The authors have stated that they have no conflicts of interest.
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