Minimal Residual Disease (MRD) Monitoring in NPM1 Mutated Acute Myeloid Leukemia (AML): Impact of Concurrent FLT3-ITD and DNMT3A Mutations on MRD Kinetics and Clinical Outcome
Authors: Kapp-Schwoerer Silke , Krönke Jan , Corbacioglu Andrea , Gaidzik Verena I. , Paschka Peter , Eiwen Karina , Späth Daniela , Göhring Gudrun , Schlegelberger Brigitte , Lübbert Michael , Kindler Thomas , Wattad Mohammed , Germing Ulrich , Nachbaur David , Fiedler Walter , Thol Felicitas , Heuser Michael , Krauter Jürgen , Ganser Arnold , Schlenk Richard F. , Döhner Hartmut , Döhner Konstanze 
Published: October 2019

Abstract

Introduction
In a recent update on MRD monitoring in 407 NPM1 mutated (NPM1mut) AML patients (pts) we could confirm the results from our previous study showing that achievement of RQ-PCR negativity after double induction (DI), after completion of therapy (CT) as well as during the follow-up period (FUP) is significantly associated with a lower cumulative incidence of relapse (CIR) and superior overall survival (OS) [Döhner K, Annals of Hematol; 2013;Suppl.1,92:S39]. In addition, in pts with concurrent FLT3-ITD (FLT3-ITDmut) or DNMT3A (DNMT3Amut) mutations, we also showed that the median NPM1mut transcript levels after each treatment cycle were significantly higher.

Aim
To evaluate the impact of concurrent FLT3-ITD and DNMT3Amut on MRD kinetics and clinical outcome in NPM1mutAML pts.

Methods
For this analysis we included all pts enrolled on one of two AMLSG treatment trials [AMLHD98A (NCT00146120) n=46; AMLSG 07-04 (NCT00151242) n=199] for whom the FLT3-ITD and DNMT3A mutation status at the time of diagnosis was determined. MRD levels (ratio NPM1mut/ABL1 transcripts x 104) were detected by NPM1mut specific RQ-PCR using TaqMan technology; the sensitivity of the assays was 10-5 - 10-6. DNMT3A and FLT3-ITD mutation status was assessed by standard PCR-based methods

Results
In total, 1588 samples [bone marrow n=1564; peripheral blood n=24] from 245 NPM1mut pts were analyzed [at diagnosis, n= 240; during therapy, n= 807; during FUP, n= 541]. FLT3-ITD and DNMT3A mutation status was available in 245/245 (FLT3-ITDmut n=94) and in 234/245 (DNMT3Amut n= 122) pts, respectively. Pre-treatment NPM1mut transcript levels did not correlate with clinical characteristics, DNMT3A or FLT3-ITD mutation status and had no impact on event-free survival, relapse-free survival and OS. Multivariable analyses stratified for FLT3-ITD mutation status after DI and CT revealed RQ-PCR negativity as a significant factor for longer remission duration (hazard ratio (HR) 15.15 and 8.95, respectively) and better OS (HR 6.13 and 4.27, respectively); DNMT3A mutation status had no significant impact in these models. Subgroup analyses showed that the proportion of pts achieving RQ-PCR negativity after DI, after CT and during FUP was significantly lower in DNMT3Amut compared to the DNMT3A wildtype pts (8.6% vs 33.3%, p=<0.001; 36,3% vs 61.9%, p=0.009; 33% vs 51%, p=0.04, respectively) whereas for FLT3-ITDmut pts this effect was only significant after DI (8.3% vs 25%, p=0.022). Based on these findings we further investigated the impact of RQ-PCR negativity in the context of concurrent FLT3-ITD and DNMT3A mutations. After DI, there was no significant difference in CIR and OS for RQ-PCR negative pts with respect to FLT3-ITD or DNMT3A mutation status. After CT, RQ-PCR negative pts with DNMT3Amut had a significantly higher CIR compared to DNMT3A wildtype pts (34% vs 8% at 4 years; p=0.007). This adverse prognostic impact was consistently seen during the FUP (CIR 21% vs 3% at 4 years; p=0.01); there was no difference in CIR rates between pts with and without FLT3-ITD mutations.

Conclusions
We demonstrate a significant correlation between the DNMT3A mutation status and the achievement of RQ-PCR negativity at all clinically relevant time points i.e. after DI, and CT, and during FUP while this strong correlation was not observed for FLT3-ITDmut. Within the NPM1mut RQ-PCR negative group the presence of DNMT3Amut allows the identification of pts at high risk of relapse. Based on our findings DNMT3A mutation status should be determined in NPM1mut pts to further refine MRD monitoring. The establishment of DNMT3Amut specific MRD assays might provide additional information on MRD status in these pts.

Disclosures:
Schlegelberger: Celgene: Consultancy. Lübbert:Johnson and Johnson: Advisory Board Other. Kindler:Novartis: Membership on an entity’s Board of Directors or advisory committees. Germing:Celgene: Honoraria, Research Funding. Schlenk:Novartis: Research Funding; Amgen: Research Funding; Pfizer: Honoraria, Research Funding; Chugai: Research Funding; Ambit: Honoraria; Celgene: Honoraria, Research Funding.