Introduction

NPM1 and FLT3-ITD mutations constitute the commonest genetic aberrations in AML, occurring in about 30% of patients (either in isolation or in combination). Their predictive potential and impact on survival outcomes has been increasingly recognised, guiding treatment decisions. The aim of our study was to evaluate the real-life impact of these mutations on survival outcomes, in a Greek population of adult patients with AML.

Materials and Methods

This is a multicentre, retrospective study of AML patients with NPM1 and /or FLT3-ITD mutations, who were diagnosed and treated from January 2020 to December 2023. The data were retrieved from the Greek AML registry. Inclusion criteria included patients treated with intensive chemotherapy (IC), bearing the NPM1 and/or the FLT3-ITD mutation. The event-free survival (EFS) and overall survival (OS) were evaluated, and a multivariate (Cox regression) analysis was performed. EFS was defined as the time from start of treatment until relapse, death or last follow-up. Not achievement of complete remission (CR) after 2 cycles of IC was considered as event. Multivariate analysis was performed with Cox proportional hazard regression analysis and the following variables were entered in the model: 1) age at diagnosis (below vs above the median), 2) the presence of NPM1 and or FLT3-ITD mutations, 3) the presence of poor prognosis Cytogenetic abnormalities, 4) the presence of MDS-related gene mutations, and 5) the presence of RAS mutations.

Results

Among the 128 patients that were included in the study, 77 were male and 61 were female. The median age at the time of diagnosis was 54 years (range 24-77). The patients were divided into three groups according to the mutation status of NPM1 and FLT3-ITD, as follows: (i) Group 1: included 55 patients with NPM1 mutation only, (ii) Group 2: 44 patients with FLT3-ITD mutation only, and (iii) Group 3: included 29 patients with NPM1 and FLT3-ITD mutations. The karyotype was normal in 106 patients and abnormal in 22 patients, with 9/22 patients having a poor prognosis karyotype (4/9 patients were NPM1-wild type). 41 out of 73 patients tested positive for additional mutations in the NGS panel, whereas another 32 patients had no other mutation identified. All patients received induction with IC (vast majority based on the 7+3 combination), with the addition of midostaurin to those positive for the FLT3-ITD mutation. Complete Remission (CR) after 2 cycles of IC was achieved in 85% (47/55 patients), 55% (24/44 patients) and 74% (22/29 patients) of Group 1, 2 and 3 patients, respectively. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) either in CR1 or beyond CR1, was performed in 13/55, 27/44 and 13/29 patients of Group 1, 2 and 3, respectively.

Multivariate analysis for EFS revealed that the only parameter associated with increased EFS was the presence of NPM1-mut in the absence of FLT3-ITD mutation. Patients in Group 1 were shown to have the best outcome (HR 1.82, 95% CI: 1.21-2.75, p=0.004), with patients in Groups 2 and 3 having comparable outcomes.

Multivariate analysis for OS revealed that age above the median was associated with decreased OS. Although patients in Group 1 had better OS compared to patients in Groups 2 and 3 (this difference did not reach significance). Notably, when the patients were censored at the time of allo-HSCT, a significant trend for improved OS was observed for patients in Group 1, compared to other patients (p=0.07).

Multivariate analysis showed that the presence of MDS-related gene mutations, RAS mutations, and poor prognosis Cytogenetic abnormalities were not associated with either EFS or OS.

Conclusions

The presence of FLT3-ITD mutation has a negative impact on outcomes, even in the era of FLT3 inhibitors. Patients with isolated NPM1 mutation (Group 1) have the best outcomes, whereas its co-existence with FLT3-ITD mutation adds no survival benefit as compared with single FLT3-ITD positive patients (at least in our study). In terms of other possible confounding factors, neither an abnormal karyotype, nor the presence of MDS-related gene, and/or RAS mutations were found to have any impact on outcomes. Allo-HSCT was the only factor identified to significantly improve the outcomes in patients with FLT3-ITD mutated AML (Groups 2 and 3) and it is therefore strongly recommended to all patients with FLT3-ITD mutated AML, irrespective of the NPM1-mutation status.

Disclosures

No relevant conflicts of interest to declare.

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2024
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