Role of autologous hematopoietic stem cell transplantation according to the NPM1/FLT3‐ITD molecular status for cytogenetically normal AML patients: A GOELAMS study

The choice of postremission therapy for acute myeloid leukemia (AML) patients is now based on the blasts' cytogenetic and molecular profile. However, the potential benefit of autologous hematopoietic stem cell transplantation (auto‐HSCT) according to the NPM1/FLT3‐ITD status has been poorly studied in AML patients with a normal karyotype (NK). Therefore, we evaluated the NPM1/FLT3‐ITD molecular status in 135 NK‐AML patients treated by allogeneic HSCT (allo‐HSCT), auto‐HSCT, or chemotherapy as consolidation therapy within the GOELAMS LAM‐2001 trial. In univariate analyzes, 4‐year leukemia‐free survival (LFS) and overall survival (OS) were significantly higher for NPM1+/FLT3‐ITD? patients compared with patients presenting another molecular profile (61 vs. 43% and 72 vs. 48%, P = 0.02 and P = 0.01, respectively). In the NPM1+/FLT3‐ITD? subgroup, there was no benefit for allo‐HSCT or auto‐HSCT vs. chemotherapy (4‐year LFS: 71, 56, and 60%; 4‐year OS: 73, 71, and 60%, respectively; P = NS). For patients with other NPM1/FLT3‐ITD molecular profiles, allo‐HSCT was found to be the best consolidation therapy, whereas auto‐HSCT was associated with a better outcome when compared with chemotherapy (allo‐HSCT‐, auto‐HSCT‐, and chemotherapy‐related 4‐year LFS: 68, 44, and 36%, P = 0.004; 4‐year OS: 68, 52, and 29%, respectively, P = 0.02). Our study indicates that allo‐HSCT and auto‐HSCT provide similar outcomes compared with chemotherapy as consolidation for NPM1+/FLT3‐ITD? NK‐AML patients. For NK‐AML patients with an adverse molecular profile, auto‐HSCT could represent an alternative therapeutic approach when no human leukocyte antigen–matched allogeneic donor is available. Am. J. Hematol. 2012. © 2012 Wiley Periodicals, Inc.     

Salvage therapy using FLT3 inhibitors may improve long‐term outcome of relapsed or refractory AML in patients with FLT3‐ITD

To determine the long‐term efficacy of FLT3 inhibitors (FLT3i) in the salvage setting for relapsed and refractory (rel/ref) acute myeloid leukemia (AML) with FLT3 internal tandem duplication (AML FLT3‐ITD), we conducted a retrospective study of 120 patients with rel/ref AML FLT3‐ITD who received salvage therapy with either FLT3i‐containing regimen (FLT3i group, N = 45) or conventional cytotoxic regimen (conventional group, N = 75). The median overall survival (OS) after the first salvage in the FLT3i group was 6·9 vs. 4·6 months in the conventional group (P = 0·17). The OS was better in the FLT3i group among patients with initial complete remission (CR) duration ≤12 months or with primary refractory disease (6·9 vs. 3·7 months; P < 0·01). The OS was better when FLT3i was combined with cytotoxic agents versus monotherapy (17 vs. 4·8 months; P = 0·017). Multivariate analysis revealed that the use of FLT3i was an independent predictor of OS (hazard ratio 0·58; 95% confidence interval, 0·38–0·88). Incorporating FLT3i into salvage strategies may improve long‐term outcome of patients with AML FLT3‐ITD. Prospective studies to validate this conclusion are warranted.     

Haematopoietic cell transplantation with and without sorafenib maintenance for patients with FLT3‐ITD acute myeloid leukaemia in first complete remission

We performed a retrospective study analysing the effect of sorafenib, an oral fms‐Like Tyrosine Kinase 3 (FLT3)/multikinase inhibitor, as post‐transplant maintenance in adult patients with FLT3‐internal tandem duplication (ITD) acute myeloid leukaemia (AML). We identified consecutive patients with FLT3‐ITD AML diagnosed between 2008 and 2014 who received haematopoietic cell transplantation (HCT) in first complete remission (CR1). Post‐HCT initiation of sorafenib (yes/no) was evaluated as a time‐varying covariate in the overall survival/progression‐free survival (OS/PFS) analysis and we performed a landmark analysis of controls alive without relapse at the median date of sorafenib initiation. We identified 26 sorafenib patients and 55 controls. Median follow‐up was 27·2 months post‐HCT for sorafenib survivors, and 38·4 months for controls (P = 0·021). The median time to initiating sorafenib was 68 days post‐HCT; 43 controls were alive without relapse at this cut‐off. Sorafenib patients had improved 2‐year OS in the d+68 landmark analysis (81% vs. 62%, P = 0·029). Sorafenib was associated with improved 2‐year PFS (82% vs. 53%, P = 0·0081) and lower 2‐year cumulative incidence of relapse (8·2% vs. 37·7%, P = 0·0077). In multivariate analysis, sorafenib significantly improved OS [Hazard ratio (HR) 0·26, P = 0·021] and PFS (HR 0·25, P = 0·016). There was no difference in 2‐year non‐relapse mortality (9·8% vs. 9·3%, P = 0·82) or 1‐year chronic graft‐versus‐host disease (55·5% vs. 37·2%, P = 0·28). These findings suggest potential benefit of post‐HCT sorafenib in FLT3‐ITD AML, and support further evaluation of post‐HCT FLT3 inhibition.     

Acute myeloid leukaemia (AML) with t(6;9)(p23;q34) is associated with poor outcome in childhood AML regardless of FLT3‐ITD status: a report from the Children's Oncology Group

Acute myeloid leukaemia (AML) with t(6;9)(p23;q34) is a rare subtype associated with FLT3‐internal tandem duplication (ITD) and poor outcomes. The clinical outcomes of paediatric patients with t(6;9) with and without FLT3‐ITD treated on six consecutive cooperative trails were evaluated. In contrast to patients without t(6;9), those with t(6;9) had a significantly lower complete remission rate, higher relapse rate (RR), and poor overall survival (OS). Within t(6;9) patients, those with and without FLT3‐ITD had an OS of 40% and 27% respectively (P > 0·9), demonstrating that t(6;9) is a high‐risk cytogenetic feature in paediatric AML and its clinical impact is independent of the presence of FLT3‐ITD.     

Identification of emerging FLT3 ITD‐positive clones during clinical remission and kinetics of disease relapse in acute myeloid leukaemia with mutated nucleophosmin

FLT3 internal tandem duplication (ITD) mutations are frequently detected at diagnosis in cytogenetically normal acute myeloid leukaemia (CN‐AML) and predict unfavourable outcome. FLT3 ITD is an unstable aberration and may be lost or acquired at relapse. Recent whole genome sequencing studies have suggested that FLT3 ITD⁺ve AML relapse may evolve from small subclones undetectable at diagnosis by routine polymerase chain reaction (PCR). We developed a patient‐specific real‐time quantitative‐PCR (RQ‐PCR) to implement FLT3 ITD detection in six AML patients whose blasts carried wild‐type FLT3 at diagnosis and who relapsed with FLT3 ITD by routine PCR. Patient‐specific forward primers were designed after cloning and sequencing the FLT3 ITD in each case. The assay allowed retrospective detection of FLT3 ITD in diagnostic samples of 4/6 cases and to establish the kinetics of clonal evolution preceding relapse. After conventional chemotherapy, all patients had early relapse despite having been classified as NPM1⁺ve/FLT3 ITD^?ve at presentation, with shorter remissions being observed in four patients re‐classified as FLT3 ITD⁺ve by the new assay. Notably, FLT3 ITD clone became detectable by conventional PCR in three patients tested during remission after initial treatment. Our data underscore the need of identifying low FLT3 ITD levels, which are probably associated with relapse in otherwise good prognosis CN‐AML.     

The kinetics of relapse in DEK‐NUP214‐positive acute myeloid leukemia patients

Preemptive treatment of relapse of acute myeloid leukemia (AML) holds the promise to improve the prognosis of this currently highly lethal condition. Proposed treatment modalities applicable in preemptive cytoreduction (e.g., demethylating agents or standard chemotherapy) differ substantially in interval from administration to antileukemic effect. The t(6;9) balanced translocation, producing the DEK‐NUP214 fusion protein, is seen in only 1% of patients with AML. We hypothesized that in these patients, who relapse with a very high frequency, a more detailed knowledge of leukemic relapse growth kinetics would improve the personalized decision‐making regarding re‐administration of chemotherapy. Based on standardized quantitative PCR data, we therefore delineated the relapse kinetics in a cohort of 27 relapsing DEK‐NUP214‐positive patients treated in four different European countries. The prerelapse leukemic burden increased with a median doubling time of 13 d (range: 5–51 d, median: 0.71 logs/month, range: 0.18–1.91 logs/month), with FLT3‐ITD‐positive patients relapsing significantly faster than FLT3‐ITD‐negative ones (median: 0.9 vs. 0.6 logs/month, Wilcoxon rank sum test, P = 0.041). Peripheral blood and bone marrow were equally useful for minimal residual disease (MRD) detection, and thus, we found that with sampling intervals of 2 months, 94% of relapses would be detected with a median time from MRD detection to hematological relapse of 64 d. In conclusion, this data provide algorithms for handling the rare patients with DEK‐NUP214‐positive AML allowing for planning of both MRD follow‐up and, upon molecular relapse, the timing of cytoreduction or possibly transplant procedures.     

The genotype nucleophosmin mutated and FLT3‐ITD negative is characterized by high bax/bcl‐2 ratio and favourable outcome in acute myeloid leukaemia

Nucleophosmin gene (NPM1) mutations characterize acute myeloid leukaemia (AML) with normal karyotype and frequently co‐exist with FLT3 internal tandem duplications (ITD). We evaluated bcl‐2, bax, NPM1 and FLT3‐ITD in 222 AML patients. Bax/bcl‐2 ratio >0·35 and NPM1 without FLT3‐ITD were significantly associated (P = 0·0001). NPM1‐mutated (mt)/FLT3‐ITD negative patients showed a higher complete remission (CR) rate (90%, P = 0·0002) and a longer overall survival (OS, P = 0·00007). NPM1‐mt/FLT3‐ITD negative plus bax/bcl‐2 > 0·35 subset showed a very high CR rate (96%), very long OS (P = 0·00005) and disease‐free survival (P = 0·004). The favourable prognosis of NPM1‐mt/FLT3‐ITD negative patients might be explained by a higher bax/bcl‐2 ratio.     

Maintenance lenalidomide in combination with 5‐azacitidine as post‐remission therapy for acute myeloid leukaemia

In this Phase 1b study, the safety and tolerability of maintenance therapy, comprising lenalidomide (0–25 mg, days 5–25) in combination with azacitidine (50–75 mg/m², days 1–5) every 28 d, was explored in 40 patients with acute myeloid leukaemia (AML) in complete remission after chemotherapy. Eligibility included AML in first complete remission (CR1) with adverse risk karyotype (n = 8), fms‐related tyrosine kinase 3‐internal tandem duplication (FLT3‐ITD) (n = 5), age ≥60 years (n = 31) or AML in second remission (CR2) (n = 14). Dose‐limiting toxicity was not reached. Common toxicities were haematological, infection, injection pain, constipation, fatigue and diarrhoea. In CR1, median relapse‐free (RFS) and overall survival (OS) was 12 and 20 months, respectively. In CR2, median RFS was 11 months, with median OS not yet reached. Among 29 patients with intermediate cytogenetic risk, RFS was 50% at 24 months. There were five patients with concomitant FLT3‐ITD and nucleophosmin (NPM1) mutation; none have relapsed and all are still alive after 17–39 months. Maintenance lenalidomide/azacitidine augmented the function of cytotoxic T lymphocytes, particularly in patients with NPM1 mutation. The lenalidomide/azacitidine maintenance combination was effective in suppressing residual DNA (cytosine‐5‐)‐methyltransferase 3 alpha (DNMT3A)‐positive disease, resulting in sustained remission in patients with concurrent NPM1 mutation. Azacitidine/lenalidomide as maintenance therapy for high‐risk AML warrants further exploration.     

High rate of hematological responses to sorafenib in FLT3‐ITD acute myeloid leukemia relapsed after allogeneic hematopoietic stem cell transplantation

Relapse represents the most significant cause of failure of allogeneic hematopoietic stem cell transplantation (HSCT) for FLT3‐ITD‐positive acute myeloid leukemia (AML), and available therapies are largely unsatisfactory. In this study, we retrospectively collected data on the off‐label use of the tyrosine kinase inhibitor sorafenib, either alone or in association with hypomethylating agents and adoptive immunotherapy, in 13 patients with post‐transplantation FLT3‐ITD‐positive AML relapses. Hematological response was documented in 12 of 13 patients (92%), and five of 13 (38%) achieved complete bone marrow remission. Treatment was overall manageable in the outpatient setting, although all patients experienced significant adverse events, especially severe cytopenias (requiring a donor stem cell boost in five patients) and typical hand‐foot syndrome. None of the patients developed graft‐vs.‐host disease following sorafenib alone, whereas this was frequently observed when this was given in association with donor T‐cell infusions. Six patients are alive and in remission at the last follow‐up, and four could be bridged to a second allogeneic HSCT, configuring a 65 ± 14% overall survival at 100 d from relapse. Taken together, our data suggest that sorafenib might represent a valid treatment option for patients with FLT3‐ITD‐positive post‐transplantation relapses, manageable also in combination with other therapeutic strategies.     

Acute myeloid leukaemia with myelodysplastic features in children: a report of Japanese Paediatric Leukaemia/Lymphoma Study Group

The clinical characteristics and prognostic relevance of acute myeloid leukaemia (AML) with myelodysplastic features remains to be clarified in children. We prospectively examined 443 newly diagnosed patients in a multicentre clinical trial for paediatric de novo AML, and found ‘AML with myelodysplasia‐related changes’ (AML‐MRC) according to the 2008 World Health Organization classification in 93 (21·0%), in whom 59 were diagnosed from myelodysplasia‐related cytogenetics alone, 28 from multilineage dysplasia alone and six from a combination of both. Compared with 111 patients with ‘AML, not otherwise specified’ (AML‐NOS), patients with ‘AML‐MRC’ presented at a younger age, with a lower white blood cell count, higher incidence of 20–30% bone marrow blasts, unfavourable cytogenetics and a lower frequency of Fms‐like tyrosine kinase 3 internal tandem duplication (FLT3‐ITD), NPM1 and CEBPA mutations. Complete remission rate and 3‐year probability of event‐free survival were significantly worse in ‘AML‐MRC’ patients (67·7 vs. 85·6%, P < 0·01, 37·1% vs. 53·8%, P = 0·02, respectively), but 3‐year overall survival and relapse‐free survival were comparable with ‘AML‐NOS’ patients. By multivariate analysis, FLT3‐ITD was solely associated with worse overall survival. These results support the distinctive features of the category ‘AML‐MRC’ even in children.     

Salvage chemotherapy followed by granulocyte colony‐stimulating factor‐primed donor leukocyte infusion with graft‐vs.‐host disease control for minimal residual disease in acute leukemia/myelodysplastic syndrome after allogeneic hematopoietic stem cell transplantation: prognostic factors and clinical outcomes

This study investigated the prognostic factors and clinical outcomes of preemptive chemotherapy followed by granulocyte colony‐stimulating factor‐primed donor leukocyte infusion (Chemo‐DLI) according to minimal residual disease (MRD) status in patients with acute leukemia and myelodysplastic syndromes who received allogeneic hematopoietic stem cell transplantation (HSCT) (n = 101). Patients received immunosuppressive drugs to prevent graft‐vs.‐host disease (GVHD) after Chemo‐DLI. The 3‐yr cumulative incidences of relapse, non‐relapse mortality, and disease‐free survival (DFS) after HSCT were 39.5%, 9.6%, and 51.7%, respectively. The cumulative incidences of relapse and DFS were significantly poorer in patients who exhibited early‐onset MRD. Forty‐four patients turned MRD negative 1 month after Chemo‐DLI; their cumulative incidences of relapse and DFS were significantly better than those with persistent MRD 1 month after preemptive Chemo‐DLI (relapse: 19.8% vs. 46.8%, P = 0.001; DFS: 69.6% vs. 46.4%, P = 0.004). The cumulative incidences of relapse and DFS after HSCT were significantly better in patients with chronic GVHD (cGVHD) than those without cGVHD (relapse: 19.6% vs. 63.7%, P < 0.001; DFS: 74.4% vs. 23.8%, P < 0.001). Early‐onset MRD, persistent MRD after Chemo‐DLI, and non‐cGVHD after Chemo‐DLI, which were associated with increased relapse and impaired DFS, suggest unsatisfactory response to preemptive Chemo‐DLI.     

Distinct factors determine the kinetics of disease relapse in adults transplanted for acute myeloid leukaemia

Background

Disease recurrence remains the major cause of death in adults with acute myeloid leukaemia (AML) treated using either intensive chemotherapy (IC) or allogenic stem cell transplantation (allo‐SCT).

Aims

The timely delivery of maintenance drug or cellular therapies represent emerging strategies with the potential to reduce relapse after both treatment modalities, but whilst the determinants of overall relapse risk have been extensively characterized the factors determining the timing of disease recurrence have not been characterized.

Materials and Methods

We have therefore examined, using a series of sequential landmark analyses, relapse kinetics in a cohort of 2028 patients who received an allo‐SCT for AML in CR1 and separately 570 patients treated with IC alone.

Results

In the first 3 months after allo‐SCT, the factors associated with an increased risk of relapse included the presence of the FLT3‐ITD (P < 0.001), patient age (P = 0.012), time interval from CR1 to transplant (P < 0.001) and donor type (P = 0.03). Relapse from 3 to 6 months was associated with a higher white cell count at diagnosis (P = 0.001), adverse‐risk cytogenetics (P < 0.001), presence of FLT3‐ITD mutation (P < 0.001) and time interval to achieve first complete remission (P = 0.013). Later relapse was associated with adverse cytogenetics, mutated NPM1, absence of chronic graft‐versus‐host disease (GVHD) and the use of in vivo T‐cell depletion. In patients treated with IC alone, the factors associated with relapse in the first 3 months were adverse‐risk cytogenetics (P < 0.001) and FLT3‐ITD status (P = 0.001). The factors predicting later relapse were the time interval from diagnosis to CR1 (P = 0.22) and time interval from CR1 to IC (P = 0.012).

Discussion and Conclusion

Taken together, these data provide novel insights into the biology of disease recurrence after both allo‐SCT and IC and have the potential to inform the design of novel maintenance strategies in both clinical settings.     

Allogeneic hematopoietic stem cell transplantation could improve survival of cytogenetically normal adult acute myeloid leukemia patients with DNMT3A mutations

DNMT3A mutations are frequent in cytogenetically normal acute myeloid leukemia (cn‐AML) patients and associated with poor survival. The role of allogeneic hematopoietic stem cell transplantation (allo‐HSCT) in DNMT3A^mut cn‐AML patients remains unclear. In this study, we retrospectively analyzed the prognostic impact of DNMT3A mutations and explored the role of allo‐HSCT in 308 cn‐AML patients who received consolidation of intensive chemotherapy or allo‐HSCT in our center from March 2005 to May 2014. In the whole cohort, 63 patients (20.5%) were identified with DNMT3A exon 23 mutations and R882H was the most frequent variant. DNMT3A^mut patients had shorter overall survival (3‐year OS: 31.9% vs. 52.0%, P = 0.009) and disease‐free survival (3‐year DFS: 21.8% vs. 40.1%, P = 0.004) compared with DNMT3A^wt patients. Based on FLT3/NPM1/CEBPA mutations, 308 cn‐AML patients were divided into favorable/intermediate group (n = 262) and unfavorable group (n = 46). There were no significant differences in 3‐year OS and 3‐year DFS between DNMT3A^mut and DNMT3A^wt patients in both favorable/intermediate and unfavorable groups. Additionally, in multivariate analysis, DNMT3A mutation remained an independent adverse prognostic factor for the survival. In the DNMT3A^mut cohort, 23 complete remission (CR) patients received allo‐HSCT consolidation and 32 CR patients received chemotherapy consolidation, dramatic differences were observed in 3‐year OS (51.7% vs. 28.9%, P = 0.048) and 3‐year DFS (41.6% vs. 14.9%, P = 0.024) between allo‐HSCT group and chemotherapy group. Collectively, DNMT3A mutation is a poor prognostic factor for cn‐AML patients and allo‐HSCT could improve survival of cn‐AML patients with DNMT3A mutations. Am. J. Hematol. 90:992–997, 2015. © 2015 Wiley Periodicals, Inc.     

Results of a phase 1 study of quizartinib as maintenance therapy in subjects with acute myeloid leukemia in remission following allogeneic hematopoietic stem cell transplant

FLT3‐ITD–mutated acute myeloid leukemia (AML) has very high risk of relapse and is associated with poor outcome following allogeneic hematopoietic‐cell transplant (allo‐HCT). This two‐part, phase 1, multicenter, open‐label, sequential‐group, dose‐escalation study aimed to determine dose‐limiting toxicities (DLTs), maximum tolerated dose (MTD), and safety/tolerability of quizartinib, a selective and highly potent FLT3 inhibitor, when administered as maintenance therapy after allo‐HCT. Thirteen subjects with documented FLT3‐ITD–mutated AML in morphological remission following allo‐HCT received one of two quizartinib dihydrochloride dose levels (DL): 40 mg/d (DL1; n = 7) and 60 mg/d (DL2; n = 6), administered orally in 28‐day cycles for up to 24 cycles. Median age of participants was 43 years. All subjects received human leukocyte antigen (HLA)‐matched allo‐HCT. One subject treated at DL1 and 1 treated at DL2 had DLTs that required drug interruption (grade 3 gastric hemorrhage and grade 3 anemia, respectively). Ten subjects (77%) received quizartinib for >1 year; 5 (38%) completed 24 cycles. Four subjects (31%) discontinued quizartinib due to adverse events. One subject (8%) experienced relapse during cycle 1 and discontinued treatment. Most common grade 3/4 adverse events were neutropenia (23%), anemia (15%), leukopenia (15%), lymphopenia (15%), and thrombocytopenia (15%). This study demonstrated acceptable tolerability and early evidence of reduced relapse rate following allo‐HCT with quizartinib maintenance compared to historical cohorts. No MTD was identified, but 60 mg daily was selected as highest dose for continuous daily administration based on randomized comparison of daily 30 and 60 mg doses in relapsed/refractory AML.     

Impact of ABCB1 single nucleotide polymorphisms 1236C>T and 2677G>T on overall survival in FLT3 wild‐type de novo AML patients with normal karyotype

Drug resistance is a clinically relevant problem in the treatment of acute myeloid leukaemia (AML). We have previously reported a relationship between single nucleotide polymorphisms (SNPs) of ABCB1, encoding the multi‐drug transporter P‐glycoprotein, and overall survival (OS) in normal karyotype (NK)‐AML. Here we extended this material, enabling subgroup analysis based on FLT3 and NPM1 status, to further elucidate the influence of ABCB1 SNPs. De novo NK‐AML patients (n = 201) were analysed for 1199G>A, 1236C>T, 2677G>T/A and 3435C>T, and correlations to outcome were investigated. FLT3 wild‐type 1236C/C patients have significantly shorter OS compared to patients carrying the variant allele; medians 20 vs. 49 months, respectively, P = 0·017. There was also an inferior outcome in FLT3 wild‐type 2677G/G patients compared to patients carrying the variant allele, median OS 20 vs. 35 months, respectively, P = 0·039. This was confirmed in Cox regression analysis. Our results indicate that ABCB1 1236C>T and 2677G>T may be used as prognostic markers to distinguish relatively high risk patients in the intermediate risk FLT3 wild‐type group, which may contribute to future individualizing of treatment strategies.     

A prognostic model for survival after salvage treatment with FLAG‐Ida +/− gemtuzumab‐ozogamicine in adult patients with refractory/relapsed acute myeloid leukaemia

The combination of fludarabine, cytarabine, idarubicin, and granulocyte colony‐stimulating factor (FLAG‐Ida) is widely used in relapsed/refractory acute myeloid leukaemia (AML). We retrospectively analysed the results of 259 adult AML patients treated as first salvage with FLAG‐Ida or FLAG‐Ida plus Gentuzumab‐Ozogamicin (FLAGO‐Ida) of the Programa Español de Tratamientos en Hematología (PETHEMA) database, developing a prognostic score system of survival in this setting (SALFLAGE score). Overall, 221 patients received FLAG‐Ida and 38 FLAGO‐Ida; 92 were older than 60 years. The complete remission (CR)/CR with incomplete blood count recovery (CRi) rate was 51%, with 9% of induction deaths. Three covariates were associated with lower CR/CRi: high‐risk cytogenetics and t(8;21) at diagnosis, no previous allogeneic stem cell transplantation (allo‐SCT) and relapse‐free interval <1 year. Allo‐SCT was performed in second CR in 60 patients (23%). The median overall survival (OS) of the entire cohort was 0·7 years, with 22% OS at 5‐years. Four independent variables were used to construct the score: cytogenetics, FLT3‐internal tandem duplication, length of relapse‐free interval and previous allo‐SCT. Using this stratification system, three groups were defined: favourable (26% of patients), intermediate (29%) and poor‐risk (45%), with an expected 5‐year OS of 52%, 26% and 7%, respectively. The SALFLAGE score discriminated a subset of patients with an acceptable long‐term outcome using FLAG‐Ida/FLAGO‐Ida regimen. The results of this retrospective analysis should be validated in independent external cohorts.     

Importance of early detection and follow-up of FLT3 mutations in patients with acute myeloid leukemia

Mutations in the fms-like tyrosine kinase 3 (FLT3) gene, such as internal tandem duplication (FLT3/ITD) in the juxtamembrane domain and point mutations in the tyrosine kinase domain, are the most common abnormalities in acute myeloid leukemia (AML). FLT3/ITD and FLT3/D835 mutations were analyzed in 113 Serbian adult AML patients using polymerase chain reaction. Twenty patients were found to be FLT3/ITD positive (17.7%). The mutations occurred most frequently in M5 and M0 subtypes of AML. They were mainly associated with the normal karyotype. All patients harboring FLT3/ITD had a higher number of white blood cells than patients without it (p = 0.027). FLT3/ITD mutations were associated with lower complete remission (CR) rate (χ ²= 5.706; p = 0.017) and shorter overall survival (OS; Log rank = 8.76; p = 0.0031). As for disease-free survival, the difference between FLT3/ITD-positive and FLT3/ITD-negative patients was not statistically significant (Log rank = 0.78; p = 0.3764). In multivariate analysis, the presence of FLT3/ITD mutations was the most significant prognostic factor for both OS and CR rate (p = 0.0287; relative risk = 1.73; 95% CI = 1.06–2.82). However, in the group of patients with the intermediate-risk karyotype, the mere presence of FLT3/ITD was not associated with inferior clinical outcome. FLT3/D835 point mutation was found in four patients (3.5%) only. Follow-up of the FLT3/ITD-positive patients revealed stability of this mutation during the course of the disease. However, changes in the pattern of FLT3/D835 mutations in initial and relapsed AML were observed. Our results indicate an association of FLT3/ITD with the adverse outcome in AML patients treated with standard induction chemotherapy. Because FLT3/ITD mutation is a target for specific therapeutic inhibition, its early detection could be helpful in clinical practice. Ms. Colovic and Ms. Tosic contributed equally to this work.     

Outcome in 146 patients with paediatric acute myeloid leukaemia treated according to the AML99 protocol in the period 2003–06 from the Japan Association of Childhood Leukaemia Study

The acute myeloid leukaemia (AML) 99 trial conducted previously in Japan for the treatment of de novo paediatric AML showed excellent results, with a 5‐year overall survival (OS) and event‐free survival (EFS) of 75·6% and 61·6%, respectively. To examine reproducibility of these results in another cohort, the outcome of 146 newly diagnosed AML paediatric patients prospectively registered in the Japan Association of Childhood Leukaemia Study (JACLS) from 2003 to 2006 was compared to that of 240 patients in the original AML 99 clinical trial. The 5‐year EFS and OS achieved in the new cohort was 66·7 ± 4·0% and 77·7 ± 8·0% respectively, which were comparable to those obtained in the original AML 99 clinical trial, although less frequent core‐binding factor (CBF) AML (29·5% vs. 37%) and an almost equal frequency of allogeneic haematopoietic stem cell transplantation (allo‐HSCT) during first complete remission (16·5% vs. 19%) were observed. The 5‐year EFS in patients with a normal karyotype (NK) (n = 35, 54·9 ± 15·1%) was inferior in the present cohort when compared to the original AML99 trial. This study confirmed the excellent outcome of the original AML99 protocol.     

Treatment of children with acute myeloid leukaemia who relapsed after allogeneic haematopoietic stem cell transplantation

Despite improvements in diagnosis and treatment, 30–40% of children with acute myeloid leukaemia (AML) experience relapse. For those who relapse after allogeneic haematopoietic stem cell transplantation (allo‐HSCT), the prognosis is particularly poor, with limited reported literature on these patients. We reviewed the clinical course of 49 children with AML (28 males, 21 females) who received allo‐HSCT between 1993 and 2011, and who had subsequently relapsed. Study endpoints included (i) complete remission (CR) rate after intensive chemotherapy, and prognostic factors for CR, (ii) disease‐free survival (DFS) and overall survival (OS) for patients who achieved CR and (iii) OS for recipients of intensive chemotherapy and prognostic factors for OS . Of the 36 patients who received intensive chemotherapy after post‐HSCT relapse, 26 (72%) achieved CR. For patients who achieved CR, 5‐year DFS and OS were 32·6 ± 10·2% and 44·4 ± 11·1%, respectively. For all recipients of intensive chemotherapy, 5‐year OS was 31·6 ± 8·7%. Cumulative incidence of treatment‐related death was 14·4%. All three recipients of second HSCT died. Amongst prognostic factors predicting improved survival, only disease status at HSCT (early first CR vs. others) proved significant in multivariate study (Hazard Ratio 2·42, 95% Confidence Interval 1·02–5·74, P = 0·045). Treatment with curative intent was able to salvage a minor but important subset of children with AML who relapsed post‐allogeneic transplant.     

Bone marrow stroma‐mediated resistance to FLT3 inhibitors in FLT3‐ITD AML is mediated by persistent activation of extracellular regulated kinase

A consistent pattern of response has been observed when FMS‐like tyrosine kinase 3 (FLT3) tyrosine kinase inhibitors (TKIs) have been used as monotherapy to treat patients with relapsed or refractory FLT3‐ internal tandem duplication (ITD) acute myeloid leukaemia (AML). Circulating blasts are cleared from the peripheral blood, while bone marrow blasts are either unaffected or are cleared from the marrow at a much slower rate. We used an in vitro model of FLT3‐ITD AML blasts co‐cultured with normal human bone marrow stromal cells to investigate the basis for this dichotomous response pattern to FLT3 inhibitors. We have found that in blasts on stroma, potent FLT3 inhibition predominantly results in cell cycle arrest rather than apoptosis. The anti‐apoptotic effect is mediated through a combination of direct cell‐cell contact and soluble factors. The addition of exogenous FLT3 ligand (FL) augments the protection, primarily by shifting the 50% inhibitory concentration for FLT3 inhibition upwards. Cytokine‐activated extracellular regulated kinase (ERK), rather than STAT5, appears to be the most important downstream signalling protein mediating the protective effect, and inhibition of MEK significantly abrogates stromal‐mediated resistance. These findings explain the phenomenon of peripheral blood versus bone marrow blast responses and suggest that the combination of potent FLT3 inhibition and MEK inhibition is a promising strategy for the treatment of FLT3‐ITD AML.