Is allogeneic transplantation really the best treatment for FLT3/ITD-positive acute myeloid leukemia? A systematic review

[Clinical study of induction chemotherapy followed by allogeneic hematopoietic stem cell transplantation in the treatment of FLT3-ITD(+) acute myeloid leukemia with normal karyotype]

Objective: To assess the efficacy of induction chemotherapy followed by allogeneic hematopoietic stem cell transplantation (allo-HSCT) in the treatment of FLT3-ITD(+) acute myeloid leukemia (AML) with normal karyotype. Methods: The clinical data of FLT3-ITD(+) AML patients with normal karyotype in the First Affiliated Hospital of Nanjing Medical University from Jan 2018 to March 2021 were retrospectively analyzed. Results: The study included 49 patients with FLT3-ITD(+)AML, 31 males, and 18 females, with a median age of 46 (16-59) years old. All patients received induction chemotherapy, and 24 patients received sequential allo-HSCT (transplantation group) . The median follow-up time was 465 days, the one-year overall survival (OS) from diagnosis was (70.0 ± 7.4) %, and one-year disease-free survival (DFS) was (70.3±7.4) %. The one-year OS was significantly different between the transplantation group and the non-transplantation group [ (85.2 ± 7.9) % vs (52.6 ± 12.3) %, P=0.049]. but one-year DFS [ (84.7 ± 8.1) % vs (55.2 ± 11.9) %, P=0.061] was not. No significance was found in one-year OS between patients with low-frequency and high-frequency FLT3-ITD(+) (P>0.05) . There were 12 patients with high-frequency FLT3-ITD(+) in the transplantation and the non-transplantation groups, respectively. The one-year OS [ (68.8 ± 15.7) % in the transplantation group vs (26.2 ± 15.3) % in the non-transplantation group, P=0.027] and one-year DFS [ (45.5 ± 21.3) % in the transplantation group vs (27.8±15.8) % in the non-transplantation group, P=0.032] were significantly different between the two groups. Conclusion: Induction chemotherapy followed by allo-HSCT can enhance the prognosis of FLT3-ITD(+) patients, particularly those with FLT3-ITD high-frequency mutation.

Hematopoietic Stem Cell Transplantation for Acute Myeloid Leukemia: An Overview of Systematic Reviews

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) has become the main treatment for acute myeloid leukemia (AML) and has been studied in many systematic reviews (SRs), but strong conclusions have not been drawn yet.

OBJECTIVE

This study aimed to summarize and critically evaluate the methodological and evidence quality of SRs and meta-analysis on this topic.

METHODS

PubMed, Embase, the Cochrane Library, and Web of Science were searched for SRs/meta-analyses regarding HSCT for AML. Two reviewers assessed the quality of SRs/meta-analyses in line with AMSTAR-2 and evaluated the strength of evidence quality with the grading of the evaluation system (GRADE) for concerned outcomes independently.

RESULTS

12 SR/Meta articles were included, and the AMSTAR-2 scale showed that the quality grade of all articles was low or very low. GRADE results showed 29 outcomes, 2 of which were high, 12 were moderate, and 15 were low. Limitations and inconsistency were the most important factors leading to degradation, followed by imprecision and publication bias. Allo-SCT had better OS and DFS benefits than auto-SCT and significantly reduced the relapse in intermediate-risk AML/CR1 patients. Auto-SCT was associated with lower TRM than allo-SCT but generally had higher relapse. The results should be confirmed further for the low or moderate evidence quality.

CONCLUSION

Current SRs show that allo-SCT in the treatment of AML might improve the OS, RFS, and DFS. Auto-SCT has significantly lower TRM but higher RR. Whether bone marrow transplantation is superior to nonmyeloablative chemotherapy remains to be evaluated. Meanwhile, the quality of methodology needs to be further improved. The intensity of evidence was uneven, and the high-quality evidence of outcomes was lacking. Considering the limitations of our overview, more rigorous and scientific studies are needed to fully explore the efficacy of different interventions of HSCT in AML, and clinicians should be more cautious in the treatment.

Pre-transplant FLT3/ITD status predicts outcome in FLT3-mutated acute myeloid leukemia following allogeneic stem cell transplantation

Acute myeloid leukemia (AML) with fetal liver tyrosine kinase 3 (FLT3) internal tandem duplication (ITD) is associated with poor prognosis, and allogeneic stem cell transplantation (Allo-SCT) seems to be the preferred therapeutic approach. However, the predictors of post-transplant outcomes were not well-defined. The aim of the study was to evaluate the significance of FLT3/ITD mutation by polymerase chain reaction as minimal residual disease (MRD) marker of outcomes after transplantation. We identified 43 patients (28 females and 15 males) with FLT3-mutated AML at the median age of 45 years who were allografted between 2009 and 2019. Hematological status at transplant was as follows: the first complete remission (CR1) in 29 patients, CR2 in 5, and 9 patients were transplanted in marrow aplasia (MA). Twenty-seven patients were FLT3 MRD negative at transplant. Median time from diagnosis to transplant was 16.7 months. Post-allograft CR rate was 88%. The relapse incidence (RI) was lower for patients who were FLT3 MRD negative at transplant when compared with those with FLT3 MRD positivity (41% vs 59%; p = 0.01). The patients who eradicated FLT3/ITD at day + 30 after transplant had lower RI than those with detectable FLT3/ITD (23% vs 76%; p = <0.001). The 2-year LFS and OS were 53% and 54%, with the median OS and LFS of 28 months and 27 months, respectively. Patients with CR1/2 and FLT3 MRD(-) had a 2-year OS of 80%. The FLT3 MRD negativity at transplant prolonged LFS in multivariate analysis (HR 5.3 95%CI 1.97-14.2); p < 0.001), whereas FLT3 MRD negativity and unrelated donor predicted favorable OS.

Clinical practice recommendation on hematopoietic stem cell transplantation for acute myeloid leukemia patients with FLT3-internal tandem duplication: a position statement from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

The FMS-like tyrosine kinase 3 (FLT3) gene is mutated in 25-30% of patients with acute myeloid leukemia (AML). Because of the poor prognosis associated with FLT3-internal tandem duplication mutated AML, allogeneic hematopoietic stem-cell transplantation (SCT) was commonly performed in first complete remission. Remarkable progress has been made in frontline treatments with the incorporation of FLT3 inhibitors and the development of highly sensitive minimal/measurable residual disease assays. Similarly, recent progress in allogeneic hematopoietic SCT includes improvement of transplant techniques, the use of haploidentical donors in patients lacking an HLA matched donor, and the introduction of FLT3 inhibitors as post-transplant maintenance therapy. Nevertheless, current transplant strategies vary between centers and differ in terms of transplant indications based on the internal tandem duplication allelic ratio and concomitant nucleophos-min-1 mutation, as well as in terms of post-transplant maintenance/consolidation. This review generated by international leukemia or transplant experts, mostly from the European Society for Blood and Marrow Transplantation, attempts to develop a position statement on best approaches for allogeneic hematopoietic SCT for AML with FLT3-internal tandem duplication including indications for and modalities of such transplants and on the potential optimization of post-transplant maintenance with FLT inhibitors.

Novel treatments for relapsed/refractory acute myeloid leukemia with FLT3 mutations

Introduction: Mutations in the gene encoding for the FMS-like tyrosine kinase 3 (FLT3) are present in about 30% of adults with AML and are associated with shorter disease-free and overall survival after initial therapy. Prognosis of relapsed/refractory AML with FLT3 mutations is even more dismal with median overall survival of a few months only. Areas covered: This review will cover current and emerging treatments for relapsed/refractory AML with FLT3 mutations, preclinical rationale and clinical trials with new encouraging data for this particularly challenging population. The authors discuss mechanisms of resistance to FLT3 inhibitors and how these insights serve to identify current and future treatments. As allogeneic stem cell transplant in the first remission is the preferred therapy for newly diagnosed AML patients with FLT3 mutations, the authors discuss the role of maintenance after SCT for the prevention of relapse. Expert opinion: Relapsed/refractory AML with FLT3 mutations remains a therapeutic challenge with currently available treatments. However, the evolution of targeted therapies with next-generation FLT3 inhibitors and their combinations with chemotherapy is showing much promise. Moreover, growing understanding of the pathways of resistance to treatment has led to the identification of various targeted therapies currently being explored, which in time will improve outcomes.

High expression of dedicator of cytokinesis 1 adversely influences the prognosis of acute myeloid leukemia patients undergoing allogeneic hematopoietic stem cell transplantation

Background: Overexpression of dedicator of cytokinesis 1 (DOCK1) has been confirmed as an unfavorable prognostic marker in acute myeloid leukemia (AML). Purpose: This study is to explore the clinical implications of DOCK1 on AML patients underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT). Patients and methods: We analyzed 71 de novo AML patients treated with allo-HSCT and divided them into two groups (DOCK1 ^high vs DOCK1 ^low) by the median expression level of DOCK1. Results: High DOCK1 expression was associated with older age (P=0.019), wild-type CEBPA (P=0.002), IDH1/2 mutations (P=0.010) and RUNX1 mutation (P=0.005). Univariate analyses showed that DOCK1 ^high and RUNX1 mutation were associated with shorter OS (P<0.001, P=0.024). Multivariate analysis confirmed the negative effect of high DOCK1 level on overall survival (P=0.010). Conclusion: Our results demonstrate that in AML patients who received allo-HSCT, high DOCK1 expression might have a persistent negative prognostic impact post-transplant.

Allogeneic Stem Cell Transplantation in Patients With FLT3-ITD Mutated AML: Transplantation in CR1 Is the Decisive Factor for Good Outcome

BACKGROUND

Patients with internal tandem duplication in fms-related tyrosine kinase receptor gene 3 (FLT3-ITD)-mutated acute myeloid leukemia (AML) have a dismal prognosis and the only curative option seems to be allogeneic stem cell transplantation (alloSCT). However, its timing is still matter of debate.

PATIENTS AND METHODS

We retrospectively analyzed 73 consecutive AML patients with FLT3-ITD (median age 53, range 20-68 years) allografted with consistent policy to try to refer them all for upfront alloSCT in first complete remission (CR1).

RESULTS

With a median follow-up of 44 (range, 5-135) months the 5-year overall survival (OS)/disease-free survival (DFS) probabilities were 49%/47%. The cumulative incidence of relapse and nonrelapse mortality (NRM) were 37% and 14%, respectively. The estimated 5-year OS for patients who received transplantation in CR1 was 62% versus 0% for patients who received transplantation beyond CR1. Multivariable analysis identified stem cell transplantation beyond CR1 as the key factor for poor OS (hazard ratio [HR], 5.41; P < .0001), DFS (HR, 4.41; P = .0002), and high relapse incidence (HR, 8.08; P < .0001). Acute graft versus host disease Grade ≥3 predicted higher NRM (HR, 3.80; P = .059) as well as inferior OS (HR, 2.04; P = .0079). No association of patient age, nucleophosmin status, donor type, conditioning, and other variables on the survival was detected.

CONCLUSION

AlloSCT should be regarded with urgency as soon as CR1 is achieved in this subset of AML patients.

Autologous Hematopoietic Stem Cell Transplantation in Acute Myelogenous Leukemia

The clinical outcomes of autologous hematopoietic stem cell transplantation (ASCT) in acute myelogenous leukemia (AML) have improved over time. Indeed, numerous studies have demonstrated that ASCT is associated with a lower relapse rate and acceptable nonrelapse mortality compared with chemotherapy alone in patients with AML. In addition, ASCT is also associated with comparable overall survival outcomes to those of allogeneic hematopoietic stem cell transplantation in some patients with AML. To date, age, cytogenetic and molecular risk stratification, and minimal residual disease (MRD) status have been shown to be closely related to clinical outcomes following ASCT. ASCT is recommended for patients with favorable-risk and intermediate-risk AML in first complete remission and patients with acute promyelocytic leukemia in second complete remission for whom a matched sibling donor is not available. MRD status pre-ASCT is the most important factor to consider when determining whether a patient is eligible for ASCT and can effectively predict clinical outcomes after ASCT. Advanced age is not an absolute contradiction for ASCT. In this review, we describe the literature and clinical trials evaluating the outcomes of ASCT in patients with AML and discuss the indications for ASCT therapy. Because the greatest concern in ASCT recipients is early relapse, important factors that should be monitored before ASCT and future perspectives in this area are also presented.

Emerging treatment paradigms with FLT3 inhibitors in acute myeloid leukemia

Mutations in the fms-like tyrosine kinase 3 (FLT3) gene are detected in approximately one-third of patients with newly diagnosed acute myeloid leukemia (AML). These consist of the more common FLT3-internal tandem duplication (ITD) in approximately 20-25% of AML cases, and point mutations in the tyrosine kinase domain (TKD) in approximately 5-10%. FLT3 mutations, especially FLT3-ITD, are associated with proliferative disease, increased risk of relapse, and inferior overall survival when treated with conventional regimens. However, the recent development of well tolerated and active FLT3 inhibitors has significantly improved the outcomes of this aggressive subtype of AML. The multikinase inhibitor midostaurin was approved by the United States Food and Drug Administration (US FDA) in April 2017 for the frontline treatment of patients with FLT3-mutated (either ITD or TKD) AML in combination with induction chemotherapy, representing the first new drug approval in AML in nearly two decades. In November 2018, the US FDA also approved the second-generation FLT3 inhibitor gilteritinib as a single agent for patients with relapsed or refractory FLT3-mutated AML. Promising phase I and II efficacy data for quizartinib is likely to lead to a third regulatory approval in relapsed/refractory AML in the near future. However, despite the significant progress made in managing FLT3-mutated AML, many questions remain regarding the best approach to integrate these inhibitors into combination regimens, and also the optimal sequencing of different FLT3 inhibitors in various clinical settings. This review comprehensively examines the FLT3 inhibitors currently in clinical development, with an emphasis on their spectra of activity against different FLT3 mutations and other kinases, clinical safety and efficacy data, and their current and future roles in the management of AML. The mechanisms of resistance to FLT3 inhibitors and potential combination strategies to overcome such resistance pathways are also discussed.

[Outcome of acute myeloid leukemia with FLT3-ITD mutation treated by allogeneic hematopoietic stem cell transplantation]

Objective: To evaluate the efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for the treatment of acute myeloid leukemia (AML) patients with FLT3-ITD mutation. Methods: From September 2008 to December 2016, 40 AML patients with FLT3-ITD mutation were enrolled in the study. The therapeutic process, outcomes and prognostic factors were retrospectively analyzed. Results: The median of WBC at initial diagnosis was 35.0 (range 1.7-185.0) ×10(9)/L. The median course number of chemotherapy was 4 (range 2-7). At the time of transplantation, 34 patients were at the first complete remission (CR(1)) stage, and the other 6 ones were non-remission after chemotherapy. 24 patients received allogeneic transplants from an HLA-matched sibling donor, 7 cases from a HLA-matched unrelated donor, the remaining 9 ones received allograft from a haploidentical donor. The rate of 3-year overall survival (OS) and disease free survival (DFS) in all patients were both 74.3% (95% CI 60.4%-88.2%). The 3-year cumulative incidences of disease relapse and non-relapse mortality were 7.5% (95%CI 1.9%-18.4%) and 18.2% (95% CI 7.9%-32.0%), respectively. More than one course of chemotherapy before achieving CR(1) and the occurrence of acute GVHD after transplantation were associated with poor outcome in terms of OS and DFS. The relapse rates were significantly lower in patients receiving transplantation at CR(1) stage [0 vs 50.0% (95%CI 77.7%-82.9%) , P<0.001] and achieving CR(1) after one course induction therapy [0 vs 16.7% (95%CI 3.9%-37.3%) , P=0.020]. Conclusions: Allo-HSCT was an efficient approach for AML patients with FLT3-ITD mutation. Patients obtained better survival, especially for those achieving CR after one course induction therapy and receiving transplantation at CR(1) stage.

Mutational spectrum and risk stratification of intermediate-risk acute myeloid leukemia patients based on next-generation sequencing

Intermediate-risk acute myeloid leukemia (IR-AML), which accounts for a substantial number of AML cases, is highly heterogeneous. Although several mutations have been identified, the heterogeneity of AML is uncertain because novel mutations have yet to be discovered. Here we applied next generation sequencing (NGS) platform to screen mutational hotspots in 410 genes relevant to hematological malignancy. IR-AML samples (N=95) were sequenced by Illumina Hiseq and mutations in 101 genes were identified. Only seven genes (CEBPA, NPM1, DNMT3A, FLT3-ITD, NRAS, IDH2 and WT1) were mutated in more than 10% of patients. Genetic interaction analysis identified several cooperative and exclusive patterns of overlapping mutations. Mutational analysis indicated some correlation between genotype and phenotype. FLT3-ITD mutations were identified as independent factors of poor prognosis, while CEBPA mutations were independent favorable factors. Co-occurrence of FLT3-ITD, NPM1 and DNMT3A mutations was identified with associated with specific clinical AML features and poor outcomes. Furthermore, by integrating multiple mutations in the survival analysis, 95 IR-AML patients could be stratified into three distinct risk groups allowing reductions in IR-AML by one-third. Our study offers deep insights into the molecular pathogenesis and biology of AML and indicated that the prognosis of IR-AML could be further stratified by different mutation combinations which may direct future treatment intervention.

Relapse risk and survival in patients with FLT3 mutated acute myeloid leukemia undergoing stem cell transplantation

In patients with AML with FMS-like tyrosine kinase 3 (FLT3) mutations, the significance of minimal residual disease (MRD) detected by PCR before allogeneic stem cell transplantation (SCT) on outcomes after transplant remains unclear. We identified 200 patients with FLT3-AML who underwent SCT at our institution. Disease status at transplant was: first or second complete remission (CR1/CR2, n = 119), high-risk CR (third or subsequent CR, marrow hypoplasia, or incomplete count recovery) (CR-HR, n = 31), and morphological evidence of active disease (AD, n = 50). The median follow-up was 27 months, and the 2-year overall and progression-free survival were 43% and 41%, respectively. Relapse was highest in the AD group (85%) and the CR-HR FLT3 MRD positive group (72%), followed by CR-HR FLT3 MRD negative (58%), CR1/CR2 FLT3 MRD positive (39%), and lowest in the CR1/CR2 FLT3 MRD negative group (23%). On multivariate analysis, independent factors influencing the risk of relapse were detectable morphological disease and FLT3 MRD by PCR pre-transplant. Factors that did not influence the relapse risk included: age, graft type, graft source, type of FLT3 mutation, or conditioning intensity. Morphologic and molecular remission status at the time of transplant were key predictors of disease relapse and survival in patients with FLT3-AML.

Pharmacologic maintenance strategies following allogeneic hematopoietic cell transplantation for acute myeloid leukemia

The use of pharmacologic agents to maintain remission following allogeneic hematopoietic cell transplantation (HCT) is a topic of increasing interest and exploration for patients with high-risk acute myeloid leukemia (AML). This review details published and ongoing studies focused on post-transplant pharmacologic maintenance for AML. While early phase studies have demonstrated the safety and tolerability of various maintenance approaches following HCT, the results of several ongoing randomized prospective studies will be required to determine the clinical efficacy needed to expand this approach from experimental to standard of care.

Integrin alphavbeta3 enhances β-catenin signaling in acute myeloid leukemia harboring Fms-like tyrosine kinase-3 internal tandem duplication mutations: implications for microenvironment influence on sorafenib sensitivity

Binding of leukemia cells to the bone marrow extracellular matrix (ECM) through integrins might influence drug response and the survival of acute myeloid leukemia (AML). However, the functions of integrin in AML are needed to be clarified. Data from The Cancer Genome Atlas (TCGA) were retrieved and integrin β3 (ITGB3) expression and prognostic significance for AML were analyzed. Integrin alphavbeta3 (αvβ3) in sorafenib sensitivity and signaling pathway of FLT3-ITD AML cells was evaluated in vitro. The level of ITGB3 expression was positively correlated with risk stratification and prognosis of AML patients, especially in cytogenetic-normal patients with Fms-like tyrosine kinase-3 internal tandem duplication (FLT3-ITD) mutation. Integrin αvβ3 decreased sorafenib sensitivity when co-culture of MV4-11 cells and bone marrow stromal cells (BMSCs), and it is crucial for osteopontin (OPN) induced sorafenib insensitivity in FLT3-ITD mutated AML cells. Mechanically, αvβ3 enhance β-catenin activation through phosphatidylinositol 3-kinase (PI3K)/Akt/Glycogen synthase kinase-3 beta (GSK3β) pathway. Moreover, genetic inhibition of β-catenin by shRNA could increase sorafenib sensitivity in MV4-11 cells. Taken together, our study revealed a novel mechanism in microenvironment influence on sorafenib sensitivity in AML with FLT3-ITD mutation that was caused by activating integrin αvβ3/PI3K/Akt/GSK3β/β-catenin pathway. Integrin αvβ3/β-catenin could be considered as a new therapeutic target for AML especially for FLT3-ITD mutated AML.

Allogeneic Hematopoietic Stem Cell Transplantation in FLT3-ITD-Positive Acute Myelogenous Leukemia: The Role for FLT3 Tyrosine Kinase Inhibitors Post-Transplantation

In recent years, allogeneic hematopoietic stem cell transplantation (allo-HSCT) has become increasingly common in patients with acute myelogenous leukemia (AML) due to improved donor availability and the use of nonmyeloablative regimens. However, despite the potential clinical gains with allo-HSCT, the post-transplantation outcomes for many patients, especially those with high-risk disease, remain dismal. Patients with AML who have internal tandem duplication mutations in the tyrosine kinase receptor FLT3 (FLT3-ITD) face particularly poor outcomes, even after allo-HSCT, which appears to only partially mitigate the poor prognosis associated with this mutation. Experimental treatments to reduce the likelihood of relapse and improve survival following allo-HSCT include maintenance with FLT3-specific tyrosine kinase inhibitors (TKIs), several of which are currently being evaluated in clinical studies. Preliminary data and case reports suggest that FLT3 TKIs can be effective in the post-transplantation setting, particularly for patients with FLT3-ITD mutations. Improvements in donor matching, transplantation procedures, and supportive care have allowed a greater number of patients to undergo allo-HSCT than ever before. For these patients, it is essential to identify effective post-transplantation therapies to reduce the risk of relapse and improve disease-free survival.