Influence of FLT3-ITD and NPM1 status on allogeneic hematopoietic cell transplant outcomes in patients with cytogenetically normal AML

Adverse impact of a high allelic burden FLT3-ITD mutation on allogeneic hematopoietic stem cell transplantation in patients with cytogenetically normal AML

Risks associated with the FLT3-ITD mutation in patients receiving chemotherapy alone for cytogenetic normal acute myeloid leukemia (CN-AML) depend on the allelic ratio (AR) and concomitant NPM1 mutation. Nevertheless, their prognostic ability after allogeneic hematopoietic cell transplantation (allo-HCT) remains undetermined. Moreover, previous studies have revealed that haploidentical transplantation improves outcomes of FLT3-ITD patients. To elucidate whether this alteration also impacts prognosis of myeloablative allo-HCT upon first remission, we retrospectively reviewed the prognostic ability of FLT3-ITD mutations in 205 CN-AML patients. Our analysis demonstrated that FLT3-ITD AR was closely related to pretransplant MRD and induction response. Multivariate analysis showed that high-AR FLT3-ITD, pretransplant MRD and induction response were independent risk factors for CN-AML. In addition, we presented evidence that the high-AR FLT3-ITD patient prognosis was not overcome by haploidentical transplantation, but was markedly improved by cGVHD. More importantly, among patients with negative pretransplant MRD, high-AR FLT3-ITD patients did not have increased relapse risk, compared to low-AR FLT3-ITD and wild-type FLT3 patients. Our findings will aid in accurate prognostic stratification of FLT3-ITD patients. We also recommend further targeted and coordinated approaches to sustain durable remission following induction chemotherapy and allo-HCT in this high-risk patient population.

Impact of FLT3 internal tandem duplication and NPM1 mutations in acute myeloid leukemia treated with allogeneic hematopoietic cell transplantation

BACKGROUND AIMS

The internal tandem duplication of FLT3 (FLT3^ITD) and NPM1 mutations (NPM1^mut) are well-established prognostic factors in cytogenetically intermediate-risk acute myeloid leukemia (AML) when treated with chemotherapy alone. However, their prognostic value in the setting of allogeneic hematopoietic cell transplantation (HCT) is controversial.

METHODS

FLT3 and NPM1 mutational status was determined at diagnosis using single-gene polymerase chain reaction or next-generation sequencing in 247 adult patients with cytogenetically intermediate-risk AML who underwent myeloablative HCT. Multivariate Fine-Gray and Cox regression was used to analyze the cumulative incidence of relapse (CIR), relapse-free survival (RFS) and overall survival (OS).

RESULTS

FLT3^ITD and NPM1^mut were present in 74 of 247 (30%) and 79 of 247 (32%) patients, respectively. There was no significant difference between patients without a FLT3^ITD or NPM1^mut (FLT3^NONITD/NPM1^WT) and patients with a FLT3^ITD mutation alone (FLT3^ITD/NPM1^WT) with regard to CIR (P = 0.60), RFS (P = 0.91) or OS (P = 0.66). Similarly, there was no significant difference between FLT3^NONITD/NPM1^WT and FLT3^NONITD/NPM1^mut patients with regard to CIR (P = 0.70), RFS (P = 0.75) or OS (P = 0.95). The presence of a concurrent mutation in NPM1 did not appear to modify the impact of having a FLT3^ITD mutation.

CONCLUSIONS

In contrast to chemotherapy-only treatment, FLT3 and NPM1 mutational status does not appear to predict outcomes in patients with cytogenetically intermediate-risk AML following HCT. These results suggest that HCT may ameliorate the poor prognostic effect of FLT3^ITD mutation and that HCT should be considered over chemotherapy-only treatment in FLT3^ITD-mutated AML.

Outcomes of pediatric acute myeloid leukemia patients with FLT3-ITD mutations in the pre-FLT3 inhibitor era

Background

Acute myeloid leukemia (AML) with internal tandem duplication in FMS-like tyrosine kinase 3 (FLT3-ITD) is associated with poor outcomes. This study aimed to analyze the outcomes of pediatric AML patients with FLT3-ITD mutations in the pre-FLT3 inhibitor era.

Methods

We retrospectively reviewed and identified 18 patients diagnosed with non-M3 AML with FLT3-ITD mutations at Seoul National University Children’s Hospital between May 2008 and August 2019.

Results

The median age was 13 years (range, 6‒19 yr). The median follow-up time was 43 months (range, 6‒157 mo). Fourteen patients received BH-AC-based (N4-Behenoy1-1-b-D-arabinofuranosy1cytosine) and 4 received cytarabine-based induction chemotherapy. Complete remission (CR) was achieved in 72.2% of the patients after the first induction chemotherapy and 80% of the patients achieved CR after salvage therapy. The overall CR rate was 94% (17/18 patients). These 17 patients underwent hematopoietic stem cell transplantation (9 matched unrelated donors, 5 matched related donors, and 3 haploidentical donors). Relapse occurred in 22% of the patients. Event free survival and overall survival rates were 53.8±12.1% and 53.6±12.1%, respectively, and they were not significantly different according to the type of induction chemotherapy (P=0.690) or the type of donor (P=0.102).

Conclusion

This study outlines the outcomes of pediatric AML patients with FLT3-ITD-mutations in one institution over a decade. Outcomes were significantly improved in this study compared to our previous report in 2004, where RFS and EFS were 0%. This study can provide baseline data for pediatric patients in the pre-FLT3 inhibitor era.

Favorable long-term survival using consolidation chemotherapy without allogeneic hematopoietic cell transplantation for acute myeloid leukemia with wild-type NPM1 without FLT3-ITD

Background

The role of allogeneic hematopoietic cell transplantation (allo-HCT) compared with consolidation chemotherapy alone in intermediate-risk acute myeloid leukemia (AML) patients with wild-type nucleophosmin/negative or a low level of Fms related tyrosine kinase 3 internal tandem duplication (NPM1 ^wt/FLT3-ITD^neg/low) has not yet been elucidated.

Methods

In this study, we retrospectively investigated 88 patients newly diagnosed with AML who received intensive induction chemotherapy at Kyungpook National University Hospital from March 2015 to July 2017. The selection criteria included the presence of results on genetic abnormalities including NPM1 and FLT3-ITD.

Results

According to the European LeukemiaNet (ELN) risk classification, 25 patients (28%) were categorized as favorable, 44 (50%) as intermediate, and 19 (22%) as adverse risk. Among the intermediate-risk patients, 40 were identified as NPM1 ^wt/FLT3-ITD^neg/low. Among the patients with NPM1 ^wt/FLT3-ITD^neg/low, complete remission (CR) was achieved in 26 patients out of 40 (65%). One-year overall survival (OS) rate was 100% in the favorable-risk group and 87.9% in the NPM1 ^wt/FLT3-ITD^neg/low group (P=0.233). Among the intermediate-risk NPM1 ^wt/FLT3-ITD^neg/low patients, there was no survival benefit with allo-HCT (N=19) compared to consolidation chemotherapy (N=21; P=0.372). In the multivariate analysis, the ELN risk group [hazard ratio (HR), 6.36; P=0.019] and the achievement of CR (HR, 2.95; P=0.017) were both identified as factors affecting OS of patients with newly diagnosed AML.

Conclusion

Among the AML patients, intermediate-risk NPM1 ^wt/FLT3-ITD^neg/low patients and favorable-risk patients showed similar OS rates. Our results suggested that allo-HCT might have limited clinical benefit for the intermediate-risk NPM1 ^wt/FLT3-ITD^neg/low patients. Well controlled studies are needed to confirm the current results.