Minimal Residual Disease Monitoring in Acute Myeloid Leukemia (AML) with Translocation t(8;21)(q22;q22): Results of the AML Study Group (AMLSG)

Abstract

Background: Acute myeloid leukemia (AML) with t(8;21)(q22;q22) results in the formation of the RUNX1-RUNX1T1 fusion transcript which can be used to monitor minimal residual disease (MRD) by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). Early identification of patients (pts) with a high risk of relapse will allow pre-emptive therapy including allogeneic hematopoietic cell transplantation (alloHCT). Recent studies in AML with NPM1 mutation or the CBFB-MYH11 gene fusion revealed that MRD persistence is significantly associated with a high risk of relapse. However, the prognostic impact of MRD assessment in RUNX1-RUNX1T1-positive AML is not well established. Aims: To assess the prognostic impact of qRT-PCR-based MRD monitoring in bone marrow (BM) of pts with t(8;21)/RUNX1-RUNX1T1-positive AML obtained at defined time-points (diagnosis, first and second cycle of chemotherapy, end of treatment). Methods: In total, 120 pts were included based on the availability of a diagnostic BM sample and at least two subsequent BM samples obtained during therapy and at the end of treatment; 106 pts were enrolled in one of six AMLSG treatment trials: AML HD93 (n=1), AML HD98A (NCT00146120; n=13), AMLSG 06-04 (NCT00151255; n=4), AMLSG 07-04 (NCT00151242; n=43), AMLSG 11-08 (NCT00850382; n=31), AMLSG 21-13 (NCT02013648; n=14); 14 pts were treated outside clinical trials. All pts received anthracycline- and cytarabine-based intensive induction followed by subsequent high-dose cytarabine consolidation cycles. For MRD assessment, qRT-PCR from BM specimens was performed using TaqMan technology; RUNX1-RUNX1T1 transcript levels (TL) were reported as the normalized value of RUNX1-RUNX1T1 per 106 transcripts of the housekeeping gene beta2-microglobulin. The maximum sensitivity of the assay was 10-6. Results: The median age of the pts was 47 years (yrs; range, 18-73 yrs); at the time of diagnosis there was a broad range of RUNX1-RUNX1T1 TL (18490 to 14440000) with a median of 227800. RUNX1-RUNX1T1 TL did not correlate with clinical features (age, WBC, platelets, LDH, BM blasts) or associated gene mutations such as KIT, FLT3-ITD/TKD, NRAS or ASXL2. However, pts with additional FLT3 mutation showed higher TL compared to wild-type pts (median, 412955 vs 219052). Cox regression analysis using RUNX1-RUNX1T1 TL as a log10 transformed continuous variable showed that higher RUNX1-RUNX1T1 TL were significantly associated with a higher cumulative incidence of relapse (CIR), inferior event-free survival (EFS) and shorter overall survival (OS) for the two time points "after first treatment cycle" and "at end of treatment" (CIR: HR, 1.84, p=0.001; HR, 1.60, p=0.03; EFS: HR, 1.59, p=0.01, HR, 1.74, p=0.01; OS: HR, 1.63, p=0.02, HR 2.13, p=0.009, respectively). In univariate analyses achievement of MRD negativity (n=35) at the end of treatment was significantly associated with a superior 4-yr OS (93% vs 67%; p=0.007) and 4-yr EFS (81% vs 61%; p=0.04) whereas achievement of MRD negativity after the first (1/85) and second (20/89) treatment cycle was low not reaching significance for any of the clinical endpoints. Separation of the RUNX1-RUNX1T1 TL according to quartiles of distribution showed significant differences in OS (p=0.04), and remission duration (p=0.006) "after first cycle" whereas "at end of treatment" significant differences were only found for OS (p=0.009). Finally, we evaluated the impact of concurrent KIT mutations on the kinetics of RUNX1-RUNX1T1 TL. Following the first treatment cycle, the median RUNX1-RUNX1T1 TL were significantly lower in the KIT wildtype group compared with the KIT mutated group (p=0.02); the same was true "at the end of treatment" (p=0.02). Conclusions: In our study, achievement of MRD negativity at the end of treatment was significantly associated with a better outcome in t(8;21)-positive AML. The fact that earlier time points did not allow the identification of pts with a high relapse risk is probably due to the high sensitivity of the qRT-PCR assay which is also reflected by the low number of pts achieving qRT-PCR negativity after first and second treatment cycle, respectively. Further analyses are ongoing including multivariable as well as molecular subgroup analyses. *These authors contributed equally to the work: MA, AC MA was supported by the Else-Kröner-Fresenius-Stiftung (EKFS). Disclosures Paschka: Celgene: Honoraria; Pfizer Pharma GmbH: Honoraria; Bristol-Myers Squibb: Honoraria; Medupdate GmbH: Honoraria; Novartis: Consultancy; ASTEX Pharmaceuticals: Consultancy. Lübbert:Ratiopharm: Other: Study drug valproic acid; Janssen-Cilag: Other: Travel Funding, Research Funding; Celgene: Other: Travel Funding. Fiedler:Amgen: Consultancy, Other: Travel, Patents & Royalties, Research Funding; Teva: Other: Travel; Kolltan: Research Funding; Ariad/Incyte: Consultancy; Novartis: Consultancy; Gilead: Other: Travel; GSO: Other: Travel; Pfizer: Research Funding. Heuser:Karyopharm Therapeutics Inc: Research Funding; Pfizer: Research Funding; Bayer Pharma AG: Research Funding; Celgene: Honoraria; Tetralogic: Research Funding; BerGenBio: Research Funding; Novartis: Consultancy, Research Funding. Schlenk:Pfizer: Honoraria, Research Funding; Amgen: Research Funding.

Clinical Challenges and Consequences of Measurable Residual Disease in Non-APL Acute Myeloid Leukemia

“…Normalized to 10 5 ABL1 copies, after only one cycle of intensive chemotherapy, MRD copy numbers of <100 in BM or <10 in PB for CBFB-MYH11 AML [16] and <500 in BM or <1000 in PB, as well as a >3 log [16] or >2.5 log [48] BM MRD reduction from diagnosis for RUNX1-RUNX1T1 AML have been shown to associate with lower relapse risk and longer OS. However, there are also studies not finding a prognostic significance at this early time-point [11,49,50]. After two cycles of chemotherapy, either absolute MRD of <0.1% (normalized to ABL1 ) [50] or a >3 log MRD reduction from diagnosis [48,49,51] associated with a lower relapse risk in both CBF-AML subtypes while MRD-negativity was no prognostic factor in RUNX1 - RUNX1T1 AML at this time-point [11].…”

“…However, there are also studies not finding a prognostic significance at this early time-point [11,49,50]. After two cycles of chemotherapy, either absolute MRD of <0.1% (normalized to ABL1 ) [50] or a >3 log MRD reduction from diagnosis [48,49,51] associated with a lower relapse risk in both CBF-AML subtypes while MRD-negativity was no prognostic factor in RUNX1 - RUNX1T1 AML at this time-point [11]. Normalized to 10 5 ABL1 copies, after three cycles of chemotherapy, MRD copy numbers of <10 in PB for CBFB-MYH11 [16] and <500 in BM, as well as a >4 log BM MRD reduction for RUNX1-RUNX1T1 AML [16] were prognostic.…”

“…Normalized to 10 5 ABL1 copies, after three cycles of chemotherapy, MRD copy numbers of <10 in PB for CBFB-MYH11 [16] and <500 in BM, as well as a >4 log BM MRD reduction for RUNX1-RUNX1T1 AML [16] were prognostic. Finally, in AML with RUNX1-RUNX1T1, BM MRD-negativity at the end of treatment was found to associate with OS and disease-free survival (DFS) or relapse probability in some studies [11,48] while another analysis only described a prognostic impact of MRD analyzed in PB [52]. In an analysis by Yin et al [16], the median time from molecular to morphologic relapse was three months in CBFB-MYH11 AML and 4.9 and 4.5 months for BM and PB, respectively, in RUNX1-RUNX1T1 AML [16,52].…”

“…However, today, MRD evaluation in AML is still only routinely used in clinical practice for treatment of acute promyelocytic leukemia (APL) for which standardized guidelines have been published [9,10]. While we still lack data from prospective, randomized clinical trials testing strategies on how to modulate treatment to alter outcomes based on the MRD status in non-APL AML, there is clear evidence that MRD assessment allows outcome prediction [11,12,13,14,15,16]. Subsequently, the most common MRD targets have been increasingly adapted for molecular and flow cytometric MRD assessment in clinical practice.…”

Measurable Residual Disease in Acute Myeloid Leukemia Using Flow Cytometry: A Review of Where We Are and Where We Are Going

“…MRD denotes the presence of leukemia cells at frequencies below that of routine measurement by morphology or cytogenetics, with sensitivity down to 1 in 10 4 to 1 in 10 6 of total leukocytes, as compared to 1 in 20 in standard morphology [ 5 ]. Numerous studies have shown the power of MRD in AML in predicting risk of relapse and overall survival [ 6 , 7 , 8 , 9 ]. In the setting of allogeneic stem cell transplant (alloSCT), those who proceed to transplant with MRD positivity have been shown to have a risk of relapse and 3-year overall survival similar to those with active AML [ 10 ].…”