Abstract: Purpose: The enhancer of zeste homolog 2 (EZH2) is a histone methyltransferase and key epigenetic regulator involved in transcriptional repression and embryonic development. Loss of EZH2 activity by inactivating mutations is associated with poor prognosis in myeloid malignancies such as MDS. More recently, EZH2 inactivation was shown to induce chemoresistance in acute myeloid leukemia (AML) (Göllner et al., 2017). Data on the frequency and prognostic role of EZH2-mutations in AML are rare and mostly confined to smaller cohorts. To investigate the prevalence and prognostic impact of this alteration in more detail, we analyzed a large cohort of AML patients (n = 1604) for EZH2 mutations. Patients and Methods: All patients analyzed had newly diagnosed AML, were registered in clinical protocols of the Study Alliance Leukemia (SAL) (AML96, AML2003 or AML60+, SORAML) and had available material at diagnosis. Screening for EZH2 mutations and associated alterations was done using Next-Generation Sequencing (NGS) (TruSight Myeloid Sequencing Panel, Illumina) on an Illumina MiSeq-system using bone marrow or peripheral blood. Detection was conducted with a defined cut-off of 5% variant allele frequency (VAF). All samples below the predefined threshold were classified as EZH2 wild type (wt). Patient clinical characteristics and co-mutations were analyzed according to the mutational status. Furthermore, multivariate analysis was used to identify the impact of EZH2 mutations on outcome. Results: EZH2-mutations were found in 63 of 1604 (4%) patients, with a median VAF of 44% (range 6-97%; median coverage 3077x). Mutations were detected within several exons (2-6; 8-12; 14-20) with highest frequencies in exons 17 and 18 (29%). The majority of detected mutations (71% missense and 29% nonsense/frameshift) were single nucleotide variants (SNVs) (87%), followed by small indel mutations. Descriptive statistics of clinical parameters and associated co-mutations revealed significant differences between EZH2-mut and -wt patients. At diagnosis, patients with EZH2 mutations were significantly older (median age 59 yrs) than EZH2-wt patients (median 56 yrs; p=0.044). In addition, significantly fewer EZH2-mut patients (71%) were diagnosed with de novo AML compared to EZH2-wt patients (84%; p=0.036). Accordingly, EZH2-mut patients had a higher rate of secondary acute myeloid leukemia (sAML) (21%), evolving from prior MDS or after prior chemotherapy (tAML) (8%; p=0.036). Also, bone marrow (and blood) blast counts differed between the two groups (EZH2-mut patients had significantly lower BM and PB blast counts; p=0.013). In contrast, no differences were observed for WBC counts, karyotype, ECOG performance status and ELN-2017 risk category compared to EZH2-wt patients. Based on cytogenetics according to the 2017 ELN criteria, 35% of EZH2-mut patients were categorized with favorable risk, 28% had intermediate and 37% adverse risk. No association was seen with -7/7q-. In the group of EZH2-mut AML patients, significantly higher rates of co-mutations were detected in RUNX1 (25%), ASXL1 (22%) and NRAS (25%) compared to EZH2-wt patients (with 10%; 8% and 15%, respectively). Vice versa, concomitant mutations in NPM1 were (non-significantly) more common in EZH2-wt patients (33%) vs EZH2-mut patients (21%). For other frequently mutated genes in AML there was no major difference between EZH2-mut and -wt patients, e.g. FLT3ITD (13%), FLT3TKD (10%) and CEBPA (24%), as well as genes encoding epigenetic modifiers, namely, DNMT3A (21%), IDH1/2 (11/14%), and TET2 (21%). The correlation of EZH2 mutational status with clinical outcomes showed no effect of EZH2 mutations on the rate of complete remission (CR), relapse free survival (RFS) and overall survival (OS) (with a median OS of 18.4 and 17.1 months for EZH2-mut and -wt patients, respectively) in the univariate analyses. Likewise, the multivariate analysis with clinical variable such as age, cytogenetics and WBC using Cox proportional hazard regression, revealed that EZH2 mutations were not an independent risk factor for OS or RFS. Conclusion EZH mutations are recurrent alterations in patients with AML. The association with certain clinical factors and typical mutations such as RUNX1 and ASXL1 points to the fact that these mutations are associated with secondary AML. Our data do not indicate that EZH2 mutations represent an independent prognostic factor. Disclosures Middeke: Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees. Rollig:Bayer: Research Funding; Janssen: Research Funding. Scholl:Jazz Pharma: Membership on an entity's Board of Directors or advisory committees; Abbivie: Other: Travel support; Alexion: Other: Travel support; MDS: Other: Travel support; Novartis: Other: Travel support; Deutsche Krebshilfe: Research Funding; Carreras Foundation: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees. Hochhaus:Pfizer: Research Funding; Incyte: Research Funding; Novartis: Research Funding; Bristol-Myers Squibb: Research Funding; Takeda: Research Funding. Brümmendorf:Janssen: Consultancy; Takeda: Consultancy; Novartis: Consultancy, Research Funding; Merck: Consultancy; Pfizer: Consultancy, Research Funding. Burchert:AOP Orphan: Honoraria, Research Funding; Bayer: Research Funding; Pfizer: Honoraria; Bristol Myers Squibb: Honoraria, Research Funding; Novartis: Research Funding. Krause:Novartis: Research Funding. Hänel:Amgen: Honoraria; Roche: Honoraria; Takeda: Honoraria; Novartis: Honoraria. Platzbecker:Celgene: Research Funding. Mayer:Eisai: Research Funding; Novartis: Research Funding; Roche: Research Funding; Johnson & Johnson: Research Funding; Affimed: Research Funding. Serve:Bayer: Research Funding. Ehninger:Cellex Gesellschaft fuer Zellgewinnung mbH: Employment, Equity Ownership; Bayer: Research Funding; GEMoaB Monoclonals GmbH: Employment, Equity Ownership. Thiede:AgenDix: Other: Ownership; Novartis: Honoraria, Research Funding.

Abstract: Cytogenetic analysis is a mandatory component in the diagnostic evaluation of acute myeloid leukemia (AML) providing information regarding the biology of the disease including response or resistance to therapy. One of the cytogenetic markers which reflect an adverse outcome in conventional chemotherapy regimens is the complex aberrant karyotype consisting of multiple unrelated cytogenetic abnormalities. In AML two definitions have been established which differ in the perception of unbalanced aberrations as well as the number of single aberrations. The ELN classification scheme adopts three unrelated abnormalities while the UK MRC recently recommended four abnormalities as the most informative cut-off of complexity in the context of an adverse prognosis. The aim of this work was to study the best cut-off defining complexity (3 vs. 4) in AML with other cytogenetic high-risk markers. Methods The databases of three clinical multicentric, randomized, and prospective SAL trials (NCT 00180115, 00180102, and 00180167) were analyzed for AML patients with multiple cytogenetic aberrations as well as normal karyotypes (control group). Unbalanced abnormalities were counted as two aberrations according to the recommendations of the MRC (i.e. a single unbalanced translocation leading to gain and loss of chromosomal material as two unique abnormalities). The following single aberrations associated with an adverse prognosis according to ELN as well as UK MRC recommendations were included: inv(3), t(3;3), abn(3q), -5, del(5q), t(5q), t(6;9), -7, add(7q)/del(7q), t(11;v)(q23;v) (except t(9;11)), and abnl(17p). Results Complete data were analyzed from 2056 patients: normal karyotype (NK) n=1590, three aberrations (K3) n=65, ≥ four aberrations (K4) n=355, t(8;21)/inv(16)/t(16;16) and at least two additional aberrations n=46. All four groups differed significantly in 5–year overall survival (OS): 35% [95% CI 32–37], 19% [95% CI 9–29] , 7% [95% CI 4–10], 67% [95% CI 53–81] , respectively, p≤0.001. The K4 group had a significant inferior 5–year OS as compared to the K3 group, 19% [95% CI 9–29] and 7% [95% CI 4–10] , p≤0.001. HSCT was performed in first remission in 25% of patients with K3 (n=16) and 17% of patients with K4 (n=59) (p=n.s.). As demonstrated earlier, multiple aberrations additional to the good risk anomalies (t(8;21), inv(16), or t(16;16)) did not impact on the favourable prognosis of the respective group. In the K3 and K4 groups single adverse risk abnormalities were found in 55% (abnl(17p) 12%) and 83% (abnl(17p) 37%) in these patients, respectively. A hyperdiploid karyotype (HDK) with gains of whole chromosomes without any structural aberration or monosomy was present in 14% of K3 and 3% of K4-patients. Interestingly, HDK with three trisomies as well as ≥ four trisomies led to a survival similar to K4 patients without HDK. Therefore, the K3 group lost its inferior survival as compared to NK when patients with adverse risk, which induce a worse prognosis per se, as well as HDK were excluded (5y–OS: 29% [9–44] vs. 35%, [95% CI 32–37] , p=n.s.). HDK patients or patients with additional single adverse risk abnormalities had a worse survival compared to NK (5y–OS: 11%, [95% CI 0–32], p=0.012; and 15%, [95% CI 3–28] , p=0.004 vs. 35%, [95% CI 32–37], respectively). In contrast, when comparing the K4 group after exclusion of adverse risk and HDK patients to NK, the K4 group remained its inferior OS as compared to NK, p 〈 0.001. Conclusions Hence, our investigation confirms and therefore favors the ≥4 cut-off of complexity in the context of an adverse prognosis as proposed by the MRC with the exception of HDK patients. HDK patients should be considered as high-risk independent of the level of complexity. Whether K3 patients without single adverse risk abnormalities and HDK should be treated as intermediate risk, as suggested by our results, needs to be investigated prospectively in clinical trials. Disclosures: Platzbecker: Celgene: Honoraria, Research Funding; Novartis: Honoraria, Research Funding.

Abstract: Background In newly diagnosed acute myeloid leukemia (AML), the general recommendation is to start treatment immediately after the diagnosis has been made. This paradigm is based both on the observation that untreated acute leukemia has a poor prognosis and on retrospective analyses demonstrating a shorter survival in younger AML patients (pts) in whom treatment was delayed by more than 5 days (Sekeres et al., 2009). A more recent single-center analysis came to a different conclusion, showing no prognostic effect for the time from diagnosis to treatment (TDT; Bertoli et al., 2013). We explored the relationship between TDT and prognosis on a large set of real-world data from the AML registry of the Study Alliance Leukemia (SAL) and compared it to the published cohorts. Methods The SAL runs a transregional AML registry in 46 treatment centers across Germany (NCT03188874). All registered patients with an intensive induction treatment, a minimum follow-up time of 12 months and no acute promyelocytic leukemia were selected (n=2,200). Treatment start was defined by the first day of cytarabine, whereas single agent hydroxyurea (HU) was labeled as pretreatment. We analyzed the influence of TDT on complete remission (CR), early death (ED) and overall survival (OS) in univariable analyses for each day of treatment delay, in groups of 0-5, 6-10, 11-15 and & gt;15 days of TDT, and by using the restricted cubic spline (RCS) method for data modelling. In order to adjust for the influence of established prognostic variables on the outcomes, we used multivariable regression models and propensity score weighting. The influence of HU pretreatment on outcomes was investigated by introducing an interaction term between TDT and the presence of HU pretreatment. Results The median age was 59 years (y) (IQR 50-68), the proportion of pts with favorable, intermediate and adverse genetic risk according to ELN was 27%, 53%, and 20%; & gt;95% of pts received induction treatment with standard 7+3. HU pretreatment was administered in 4% of pts. The median TDT was 3 days (IQR 2-6). Descriptive statistics after grouping of pts showed the highest median age and the lowest proportion of NPM1 mutated and favorable risk in the TDT group 11-15. Of all pts, 79% achieved a CR/CRi; unadjusted CR rates for the patient groups with TDT of 0-5, 6-10, 11-15 and & gt;15 days were 80%, 77%, 74% and 76%, respectively (p=0.317). In multivariable analysis accounting for the influence of ELN risk, age, WBC, LDH, de novo versus secondary AML and ECOG, the OR for each additional day of TDT was 0.99 (95%-CI, 0.97-1.00; p=0.124). Four percent of pts died within the first 30 days from treatment start. The respective rates in the four TDT categories were 4.0%, 3.8%, 5.1% and 4.1% (p=0.960). In multivariable analysis, the OR for TDT was 1.01 (95%-CI, 0.98-1.05; p=0.549). After a median follow-up of 40 months, the 2-y OS of all pts was 51%. The unadjusted 2-y OS rates stratified by TDT of 0-5, 6-10, 11-15, & gt;15 days were 52, 49, 46, and 51% (see Table 1 and Figure 1). The hazard ratio (HR) for each day of treatment delay was 1.00 (95%-CI; 0.99-1.01; p=0.317). In multivariable Cox regression analysis, the HR for TDT as continuous variable was 1.00 (95%-CI, 0.99-1.01; p=0.689). When OS was analyzed separately stratified for age ≤60 and & gt;60 ys and for high versus lower initial WBC defined by a threshold of 50 x 109/L, no significant differences between TDT groups were observed. Multivariable models using TDT as a grouped variable or with RCS did not provide evidence for a significant influence of TDT on outcomes. Propensity score matching of pts in the four TDT groups did not reveal an influence on outcomes. The use of HU was not associated with CR, ED nor OS. Conclusion Our study on 2,200 newly diagnosed registry pts receiving consistent intensive induction with standard-dose cytarabine plus daunorubicin (7+3) suggests that TDT is not related to response or survival, neither in younger nor in older pts. Despite multivariable analyses, a bias towards longer TDT intervals in pts judged to be clinically stable by the treating physician cannot be excluded entirely. As treatment stratification in intensive first-line treatment of AML evolves, the TDT data suggests that it may be a safe and reasonable approach to wait for genetic and other laboratory test results in order to assign clinically stable pts to the best available treatment option before the start of intensive treatment. Disclosures Krämer: Daiichi-Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding; BMS: Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Hänel:Roche: Honoraria; Amgen: Honoraria; Celgene: Other: advisory board; Novartis: Honoraria; Takeda: Other: advisory board. Jost:Daiichi: Honoraria; Sanofi: Honoraria; Gilead: Other: travel grants; Jazz Pharmaceuticals: Honoraria. Brümmendorf:Merck: Consultancy; Janssen: Consultancy; Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; University Hospital of the RWTH Aachen: Employment; Ariad: Consultancy. Krause:Siemens: Research Funding; Takeda: Honoraria; MSD: Honoraria; Gilead: Other: travel; Celgene Corporation: Other: Travel. Scholl:Novartis: Other: Project funding; Pfizer: Other: Advisory boards; Gilead: Other: Project funding; Daiichi Sankyo: Other: Advisory boards; AbbVie: Other: Advisory boards. Hochhaus:Pfizer: Research Funding; Novartis: Research Funding; BMS: Research Funding; Incyte: Research Funding; MSD: Research Funding. Kiani:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Middeke:Sanofi: Research Funding, Speakers Bureau; Roche: Speakers Bureau; AbbVie: Consultancy, Speakers Bureau; Gilead: Consultancy; Janssen: Consultancy, Speakers Bureau; MSD: Consultancy. Thiede:AgenDix GmbH: Employment, Equity Ownership; Novartis: Research Funding, Speakers Bureau; Bayer: Research Funding; Daiichi-Sankyo: Speakers Bureau. Stoelzel:JAZZ Pharmaceuticals: Consultancy; Neovii: Other: Travel funding; Shire: Consultancy, Other: Travel funding. Platzbecker:Celgene: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding.

Abstract: The presence of a mutated nucleophosmin-1 gene (NPM1 mut ) in acute myeloid leukemia (AML) is associated with a favorable prognosis. To assess the predictive value with regard to allogeneic stem-cell transplantation (SCT), we compared the clinical course of patients with NPM1 mut AML eligible for allogeneic SCT in a donor versus no-donor analysis. Patients and Methods Of 1,179 patients with AML (age 18 to 60 years) treated in the Study Alliance Leukemia AML 2003 trial, we identified all NPM1 mut patients with an intermediate-risk karyotype. According to the trial protocol, patients were intended to receive an allogeneic SCT if an HLA-identical sibling donor was available. Patients with no available donor received consolidation or autologous SCT. We compared relapse-free survival (RFS) and overall survival (OS) depending on the availability of a suitable donor. Results Of 304 eligible patients, 77 patients had a sibling donor and 227 had no available matched family donor. The 3-year RFS rates in the donor and no-donor groups were 71% and 47%, respectively (P = .005); OS rates were 70% and 60%, respectively (P = .114). In patients with normal karyotype and no FLT3 internal tandem duplication (n = 148), the 3-year RFS rates in the donor and no-donor groups were 83% and 53%, respectively (P = .004); and the 3-year OS rates were 81% and 75%, respectively (P = .300). Conclusion Allogeneic SCT led to a significantly prolonged RFS in patients with NPM1 mut AML. The absence of a statistically significant difference in OS is most likely a result of the fact that NPM1 mut patients who experienced relapse responded well to salvage treatment. Allogeneic SCT in first remission has potent antileukemic efficacy and is a valuable treatment option in patients with NPM1 mut AML with a sibling donor.

Abstract: Biallelic mutations of the CEBPA gene (CEBPAbi) define a distinct entity associated with favorable prognosis; however, the role of monoallelic mutations (CEBPAsm) is poorly understood. We retrospectively analyzed 4708 adults with acute myeloid leukemia (AML) who had been recruited into the Study Alliance Leukemia trials, to investigate the prognostic impact of CEBPAsm. CEBPA mutations were identified in 240 patients (5.1%): 131 CEBPAbi and 109 CEBPAsm (60 affecting the N-terminal transactivation domains [CEBPAsmTAD] and 49 the C-terminal DNA-binding or basic leucine zipper region [CEBPAsmbZIP] ). Interestingly, patients carrying CEBPAbi or CEBPAsmbZIP shared several clinical factors: they were significantly younger (median, 46 and 50 years, respectively) and had higher white blood cell (WBC) counts at diagnosis (median, 23.7 × 109/L and 35.7 × 109/L) than patients with CEBPAsmTAD (median age, 63 years, median WBC 13.1 × 109/L; P & lt; .001). Co-mutations were similar in both groups: GATA2 mutations (35.1% CEBPAbi; 36.7% CEBPAsmbZIP vs 6.7% CEBPAsmTAD; P & lt; .001) or NPM1 mutations (3.1% CEBPAbi; 8.2% CEBPAsmbZIP vs 38.3% CEBPAsmTAD; P & lt; .001). CEBPAbi and CEBPAsmbZIP, but not CEBPAsmTAD were associated with significantly improved overall (OS; median 103 and 63 vs 13 months) and event-free survival (EFS; median, 20.7 and 17.1 months vs 5.7 months), in univariate and multivariable analyses. Additional analyses revealed that the clinical and molecular features as well as the favorable survival were confined to patients with in-frame mutations in bZIP (CEBPAbZIP-inf). When patients were classified according to CEBPAbZIP-inf and CEBPAother (including CEBPAsmTAD and non-CEBPAbZIP-inf), only patients bearing CEBPAbZIP-inf showed superior complete remission rates and the longest median OS and EFS, arguing for a previously undefined prognostic role of this type of mutation.

Abstract: Background Double induction using two subsequent 7+3 regimens of cytarabine plus anthracycline is commonly performed in AML patients with an adequate performance status in order to maximize dose intensity upfront. However, for patients with a good early response at day 15 of first induction, there is no prospective randomized evidence on the necessity or value of a second induction cycle. Aims In order to answer the question if good responders of the first 7+3 induction could be spared a second induction cycle, we set up randomized-controlled SAL DaunoDouble trial. The study prospectively assesses the outcome of patients with a good early response with respect to the number of induction cycles (single versus double). We assumed non-inferiority of single induction in terms of complete remission (CR/CRi) rate, based on a margin of 7.5%. Here, we present the results of the planned interim analysis. Methods Patients (pts) 18-65 years with newly diagnosed AML, normal cardiac and organ function received a first induction cycle with seven days of cytarabine plus three days of daunorubicin ("7+3"). Response assessment in bone marrow was done on day 15 after the initiation of chemotherapy and confirmed by central review. A blast count & lt;5% was defined as good response. Pts with good response were randomized to receive a second induction cycle (arm D) or no second induction cycle (arm S). Primary endpoint was CR/CRi after completion of induction, secondary endpoints were RFS, and OS. Results Between 2014 and 2020, 624 evaluable pts were enrolled and received the first induction cycle with 7+3. A marrow blast clearance below 5% on day 15 was achieved in 298 pts (48%), providing eligibility for randomization. Of these patients, 150 were randomized into arm S and 148 into arm D, respectively. Median age was 52 years, 92% had de novo AML, NPM1 mutation was present in 53%, FLT3-ITD in 25% of pts. Favorable, intermediate and adverse risk (ELN 2017) were present in 56%, 34% and 10% of pts, respectively. CR/CRi rates at the end of induction were 86% after single induction and 85% after double induction. The CR/CRi rates in 224 pre-defined per-protocol pts were 88% versus 91%, resulting in a CR difference of 3% (95%-CI -0.047-0.111; p for non-inferiority test 0.145). After a median follow-up time of 24 months, RFS was slightly but not significantly lower after single induction with a 3-year RFS of 53% versus 64% (HR 1.4, p=0.125), whereas no differences were seen in 3-year OS, with a of rate of 74% versus 75% (HR 1.1, p=0.645) after single versus double induction. Conclusion The interim analysis results show that in good responders, the difference between CR rates after single versus double induction was even smaller than the predefined 7.5% margin, suggesting a trend for non-inferiority of single induction, although statistical significance was not reached. The trial continued recruitment. These findings suggest that in good responders, it may be safe to omit a second induction cycle if a second cycle poses a high risk. Figure. CR + CRi, RFS and OS after randomization to single versus double induction. Disclosures Alakel: Pfizer: Consultancy. Jost:Pfizer: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; JAZZ: Other: travel support; Celgene: Other: travel support. Novak:Roche: Consultancy; Janssen: Other: Travel expenses; Takeda: Consultancy; Amgen: Consultancy, Other: Travel expenses; Pfizer: Consultancy; Novartis: Consultancy. Krause:Takeda: Honoraria; Celgene: Other: Travel Support; MSD: Honoraria; Pfizer: Honoraria; Siemens: Research Funding; Gilead: Other: Travel Support. Held:Roche: Consultancy, Other: Travel, Accommodations, Expenses, Research Funding; BMS: Consultancy, Other: Travel, Accommodations, Expenses, Research Funding; MSD: Consultancy; Acrotech: Research Funding; Spectrum: Research Funding; Amgen: Research Funding. Platzbecker:AbbVie: Consultancy, Honoraria; Amgen: Honoraria, Research Funding; Geron: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria. Thiede:AgenDix GmbH: Other: Co-owner and CEO. Müller-Tidow:Daiichi Sankyo: Research Funding; Pfizer: Research Funding, Speakers Bureau; BiolineRx: Research Funding; Janssen-Cilag GmbH: Speakers Bureau.

Abstract: Background: Measurable residual disease (MRD) can identify patients (pts) with myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) in complete hematological remission (CR) at high risk of relapse even after allogeneic hematopoietic stem cell transplantation (HSCT). We have recently shown in 53 pts treated within the first cohort of the RELAZA2 trial that pre-emptive therapy with azacitidine (AZA) at the time of MRD-positivity (MRDpos) can successfully prevent imminent hematological relapse (Platzbecker et al. Lancet Oncol. 2018). We now report on the results of the second cohort of 41 pts undergoing MRD-guided treatment in the RELAZA2 trial (ClinicalTrials.gov NCT01462578) by the Study Alliance Leukemia (SAL). Methods: Between 2015 and 2018, 166 MDS/AML pts were screened and centrally monitored for MRD in bone marrow or peripheral blood at monthly intervals for a period of 2 years prospectively in 9 centers in Germany. Of these 166, 41 pts with either advanced MDS (n=6) or AML (n=35) in CR after either conventional chemotherapy only (n=13) or consecutive allogeneic HSCT (n=28) developed MRD above a threshold defining imminent hematological relapse. Still being in morphological CR, these pts pre-emptively received 6 cycles of AZA (75mg/m2, s.c. days 1-7), which was followed by a risk-adapted AZA-maintenance therapy based on MRD-response for up to 18 additional months. Pts developing a hematological relapse went off study. MRD was detected by either the quantification of NPM1 mutation level (n=19), leukemia-specific fusion genes DEK-NUP214 (n=1) or RUNX1/RUNX1T1 (n=2) or a sensitive donor chimerism analysis of sorted CD34(+)/CD117(+) peripheral blood cells (n=28) in pts undergoing allogeneic HSCT. Here, we report the analysis of the primary endpoint of the 41 pts in the second cohort as well as the data for the entire 94 pts who entered the treatment phase of the RELAZA-2 study. Results: At a median of 110 days (range 28-476) after start of screening, 41 (25%) out of 166 prospectively screened pts became MRDpos as defined by either a decrease of CD34(+)/CD117(+) donor chimerism to & lt;80% (n=23) or a detectable mutation level & gt;1% (NPM1 n=18) while being still in hematological CR. All of these MRDpos pts started AZA-based pre-emptive treatment to prevent imminent hematological relapse. Six months after start of MRD-guided therapy, 25 out of 41 pts were still in CR (61%, 95%-CI 45-76%, p & lt;0.001, one-sided binomial test for H0: pexp≤0.3) while a total of 15 pts (37%) developed hematologic relapse after median of 3 AZA cycles. In fact, 19 pts (46%) responded with either a decline of MRD below a predefined threshold (increasing CD34(+) donor chimerism to ≥80% or mutation level & lt;1%), while a stabilization in the absence of relapse was achieved in 6 pts (15%). Overall response rate was not statistically different between pts with (57%) or without (69%) antecedent allogeneic HSCT (p=0.5). After 6 months of initiation of MRD-guided treatment, 21 pts (51%) continued to receive a median of 6 (range 1-15) subsequent AZA cycles. Eventually, hematologic relapse occurred in 6 of those pts (29%), but was delayed until a median of 320 days (range 219-375 days) after initial MRD detection. With a median follow-up of 9 months after start of MRD-guided pre-emptive treatment the 12-months overall and progression free survival rate is 94% and 44%, respectively. When combining results for the primary endpoint with the first cohort, the 6 months relapse free survival for all 94 pts was 60% (56/94 pts.; 49-70%; p & lt;.001 one-sided binomial test for H0: pexp≤0.3; Fig. 1). Conclusion: These multicenter prospective data provide further strong evidence that continuous MRD monitoring is feasible and can identify MDS/AML pts at high risk of hematological relapse. Pre-emptive MRD-guided therapy with AZA is an effective treatment to prevent or at least substantially delay hematologic relapse in these pts. Disclosures Platzbecker: Novartis: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria. Wolf:Celgene: Honoraria, Research Funding; Abbvie: Honoraria. Krämer:Daiichi-Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding. Bug:Gilead Sciences: Membership on an entity's Board of Directors or advisory committees, Other: Travel grants; Jazz Pharmaceuticals: Honoraria; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel grants; Hexal: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees; Sanofi: Other: travel grants; Celgene Neovii: Other: travel grant. Götze:AbbVie: Membership on an entity's Board of Directors or advisory committees. Stelljes:Novartis: Honoraria; Amgen: Honoraria; Jazz Pharmaceuticals: Honoraria; Pfizer: Consultancy, Honoraria, Research Funding; MDS: Consultancy. Subklewe:AMGEN: Consultancy, Honoraria, Research Funding; Gilead: Consultancy, Honoraria, Research Funding; Miltenyi: Research Funding; Oxford Biotherapeutics: Research Funding; Janssen: Consultancy; Roche: Consultancy, Research Funding; Pfizer: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Morphosys: Research Funding. Hänel:Celgene: Other: advisory board; Novartis: Honoraria; Takeda: Other: advisory board; Amgen: Honoraria; Roche: Honoraria. Dührsen:Gilead: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Alexion: Honoraria; Takeda: Consultancy, Honoraria; Teva: Honoraria; Celgene: Research Funding; Roche: Honoraria, Research Funding; AbbVie: Consultancy, Honoraria; Janssen: Honoraria; Amgen: Consultancy, Honoraria, Research Funding; CPT: Consultancy, Honoraria. Müller-Tidow:MSD: Membership on an entity's Board of Directors or advisory committees. Thiede:Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau; AgenDix GmbH: Employment, Equity Ownership.

Abstract: Background: Most patients (pts) diagnosed with Acute Myeloid Leukemia (AML) are older than 60 years. Although intensive induction chemotherapy in medically fit pts is still the standard practice and a prerequisite for long-term survival, elderly pts have a higher risk of treatment related morbidity and lower remission rates than younger AML pts. An optimized induction treatment would combine high complete remission (CR) rates with tolerable toxicity. The combination of intermediate-dose cytarabine plus mitoxantrone (IMA) has been reported to result in high CR rates (73.5%) with acceptable toxicity in 86 elderly AML pts (Niederwieser et al., Blood 2002, abstr. 1337). We present the mature final results of a randomized-controlled trial comparing efficacy and tolerability of IMA with the standard 7+3 induction regimen consisting of daunorubicin plus cytarabine (DA). Patients and Methods: In the 60+ trial of the Study Alliance Leukemia (SAL), AML pts 〉 60 years and medically fit for chemotherapy were randomized to receive either intermediate-dose cytarabine (1000 mg/m2 BID days 1,3,5,7) plus mitoxantrone (10 mg/m2 days 1-3) (IMA) or standard induction therapy with cytarabine (100 mg/m2 continuously days 1-7) plus daunorubicin (45 mg/m2 days 3-5) (DA). All pts in CR after DA received intermediate-dose cytarabine plus amsacrine (MAMAC) as consolidation treatment, whereas pts in CR after IMA were consolidated with standard-dose cytarabine plus mitoxantrone (2+5). Primary study endpoint was the CR rate with an expected difference of 15% in favor of IMA. Secondary endpoints were the incidence of serious adverse events (SAEs), time to relapse (TTR), relapse-free survival (RFS), and overall survival (OS). Results: Between February 2005 and October 2009, 852 pts were screened for study inclusion and 485 pts started study treatment, of which 241 pts were randomized for treatment arm A (DA) and 244 for treatment arm B (IMA). The median age was 69 years. Pt characteristics were equally distributed between the two arms. According to a strict definition, all patients with early death, study drop-out, or failed remission assessment were categorized as being not in CR. The CR rate amongst all 485 pts treated in the study was 47%. The CR rate after DA was 39% (95%-CI; 33-45) versus 55% (95%-CI; 49-61) after IMA (OR 1.89, p=0.001). If all first CRs were taken into account including those achieved after trial discontinuation, the CR rates after DA versus IMA induction were 55% versus 64% (p=0.043). Separate analyses addressing age, cytogenetics, de novo AML, NPM1 and FLT3-ITD confirmed higher CR rates after IMA induction throughout these subgroups. Six-week mortality was 14% in both arms. The median duration of ≥ grade 3 neutropenia was 23 days after DA I and 25 days after IMA (p=0.031). The median duration of thrombocytopenia ≥ grade 3 was 16 versus 20 days after DA I and IMA I, respectively (p 〈 0.001). The incidences of non-hematologic toxicities were not significantly different except for a higher incidence of liver toxicity (odds ratio IMA/DA = 0.52; p=0.001) and gastrointestinal symptoms (OR IMA/DA = 0.62; p=0.041) after DA. In the course of treatment, 11 pts in each arm (5%) received allogeneic stem cell transplantation. After a median follow-up of 66 months, RFS curves are superimposable in the first year with a similar median RFS of 11 months and 10 months after DA and IMA, respectively. However, a separation of RFS curves developed with longer follow up, resulting in 1-year RFS rates of 45% versus 46%, but 3-year RFS rates of 29% versus 14% in the DA versus IMA arms, respectively (p=0.042). The median OS for all randomized pts was 10 months in both arms; 1-year and 3-year OS rates were 45% and 19% after DA versus 44% and 19% after IMA (p=0.513). Conclusion: The results indicate that elderly AML pts benefit from a dose escalation of cytarabine in induction therapy by significantly higher CR rates and similar toxicity compared to a standard 7+3 approach. In our trial, this did not translate into a survival advantage, most likely due to differences in consolidation treatment of the respective treatment arms. In combination with an effective consolidation strategy such as high-dose cytarabine or allogeneic transplantation, our current results favor the use of intermediate dose cytarabine in induction for pts with a curative AML treatment approach. Figure 1. CR rates depending on induction treatment Figure 1. CR rates depending on induction treatment Disclosures Einsele: Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Amgen/Onyx: Consultancy, Honoraria, Speakers Bureau. Thiede:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AgenDix GmBH: Equity Ownership. Platzbecker:Amgen, Inc.: Honoraria; GlaxoSmithKline: Honoraria, Research Funding; Celgene: Honoraria; Novartis: Honoraria. Ehninger:Cellex GmbH: Equity Ownership.

Abstract: Mutations of the key myeloid transcription factor CCAAT/enhancer binding protein alpha (C/EBPa) are found in 5-10% of patients with acute myeloid leukemia (AML). Two mutational clusters exist, in the aminoterminal transcription activation domains (TAD1 or 2) and in the basic leucine zipper domain (bZIP) located at the carboxyterminal-part of the protein. Biallelic mutations (biCEBPA) have been found to be associated with improved outcome and are now included as an independent entity in the WHO-classification. In contrast, monoallelic CEBPA-mutations (moCEBPA) do not appear to provide prognostic information. We characterized a large cohort of AML patients for CEBPA mutations and further analyzed the mutational spectrum of mono- and biallelic CEBPA-mutant AML patients to better understand potential differences in the biology of these groups. Patients and Methods: Patients (including all age groups) analyzed had a newly diagnosed AML and were registered in clinical protocols of the Study Alliance Leukemia (SAL)(AML96, AML2003 or AML60+, SORAML) or the SAL-register. Screening for CEBPA mutations was done using PCR and capillary electrophoresis. All identified CEBPA mutations were confirmed using conventional Sanger sequencing and the samples were further analyzed using next generation sequencing (Trusight Myeloid Panel, Illumina) for the presence of associated alterations. Results: In the 4578 patients analyzed, 228 (5%) with CEBPA-mutations were identified. An initial analysis revealed substantial clinical differences between the different mutation subtypes. Patients with biCEBPA (n=111) were significantly younger (median age 46 yrs) than wt-CEBPA patients (median 57 yrs; p 〈 .001). Interestingly, single bZIP mutant patients (n=64) had a similar median age (50 yrs.) as biCEBPA, whereas single TAD mutant patients (n=53) were significantly older (median 63 yrs.). In addition, WBC counts, CD34 positivity as well as the history of prior MDS differed between the subgroups (single TAD mutant had significantly lower WBC counts, lower rate of CD34 positivity and had a higher rate of prior MDS than biCEBPA and single bZIP mutant patients). Along with this, the distribution of co-mutations differed significantly between the subgroups, especially GATA2 mutations were more common in biCEBPA and single bZIP mutant patients (37% and 34%, respectively) compared to only 3% (single TAD)(p=.001). A similar pattern was seen for mutations in DNMT3A (8% biCEBPA, 20% single bZIP vs. 36% single TAD; p=.001), and NPM1 (3% biCEBPA, 8% single bZIP, 32% single TAD; p 〈 .001). In 2897 patients, the different CEBPA mutations were correlated with outcome. This analysis indicated a differential effect of the individual mutations on outcome, with an improved rate of complete remission (CR), overall survival (OS) and event free survival (EFS) for biCEBPA and single bZIP mutations in univariate and multivariate analyses (shown for OS in Figure 1a). Given the similarity of single bZIP and biCEBPA mutations, it appears reasonable to speculate on a common mechanistical background, since most of the biCEBPA mutants include a bZIP alteration. Recent experimental evidence generated by several groups indeed supports a specific role of these bZIP missense mutations. To address this in the clinical context, we regrouped patients with mutant CEBPA into patients with (n=157) or without bZIP mutations (n=71), irrespective of the biallelic status. As illustrated in Figure 1b, the bZIP mutant group had a significantly better OS, similar results were obtained for EFS and CR. In multivariate analysis, the presence of a bZIP mutation was the strongest indicator for achievement of CR (HR 7.5, 95% CI: 3-19; p 〈 .001), and together with favorable cytogenetics the factor associated with best OS (HR: .48; 95% CI .36-.64; p 〈 .001). In conclusion, our results obtained in one of the largest cohorts of AML patients analyzed for CEBPA mutations indicate that especially the presence of a missense bZIP mutation is associated with a favorable outcome in AML patients. These data point to substantial differences in prognostic implications of individual CEBPA mutations and support the major functional divergence of these alterations. If confirmed, these results might necessitate further refinement of their use in AML-classification. Disclosures Middeke: Sanofi: Honoraria. Platzbecker:Janssen-Cilag: Honoraria, Research Funding; Celgene Corporation: Honoraria, Research Funding; TEVA Pharmaceutical Industries: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Thiede:AgenDix: Employment, Other: Ownership.

Abstract: Background: So called triple-negative acute myeloid leukemias (AML) form a heterogeneous subgroup of intermediate-risk AML according to ELN criteria. Molecularly this group can be defined by the absence of internal tandem duplications (ITDs) in the fms related tyrosine kinase 3 gene (FLT3), wild type (wt) nucleophosmin gene (NPM1) and wt or single (homozygously or heterozygously) mutated CCAAT/enhancer binding protein α gene (CEBPA). To date, it remains unclear whether this group of patients benefits from allogeneic stem cell transplantation (alloSCT) as consolidation strategy in first complete remission (CR1). Aims: To evaluate the impact of alloSCT on the overall (OS) and relapse free survival (RFS) in patients with triple negative AML in first remission in comparison to post remission chemotherapy (PRT). Methods: We performed a subgroup analysis of 3041 AML patients aged 16-60 years who were enrolled into the AML 96 and the AML 2003 trials of the Study Alliance Leukemia (SAL). Selection criteria for this subgroup were NPM1 wt, negativity for FLT3-ITD and CEPBA double mutations, a karyotype that does not define the AML as favorable or adverse according to ELN criteria and the accomplishment of CR1. Status of molecular markers was evaluated with standard PCR techniques. Within the AML2003 trial, donor status was evaluated at study entry, making these data eligible for a donor-versus-no-donor analysis. Kaplan-Meier estimates were used to report on point estimates for survival probabilities. Multivariate Cox models were fitted to analyze the impact of alloSCT as time-dependent covariate. Age, gender, white blood cell count, lactate dehydrogenase, AML type (de novo, secondary AML following MDS or MPN, or therapy-related myeloid neoplasms) and ECOG performance status at diagnosis were selected as adjusting covariables. As-treated analyses used data from both trials, AML96 and AML2003. For these analyses alloSCT or PRT were entered as time-dependent covariates into extended Cox regression models. Survival outcomes were displayed with Simon-Makuch-plots. Results: In total, 497 patients (AML96: 217, AML2003: 280) with a median age of 47 years were evaluable for the analysis of OS from diagnosis. A total of 302 patients had reached CR1 and could be evaluated for RFS. In a multivariate donor-versus-no-donor analysis, OS of patients with a sibling donor was not significantly different to patients without a donor (HR 0.79, 95%CI 0.53 to 1.16, p=.2). Irrespective of whether the patient actually received alloSCT in CR1, the probability of OS at 5 years from study enrollment was 55% (95%CI, 45% to 67%) for patients with a sibling donor and 47% (95%CI, 40% to 54%) for patients without a donor. For RFS, the hazard ratio was 0.72 (95%CI, 0.5 to 1.05, p=0.09), with a trend in favor of better remission-control for patients with a sibling donor. At five years from CR1, RFS of patients with sibling donor was 48% (95%CI, 38% to 61%) compared to 36% (95%CI, 30% to 44%). However, the transplantation rate in the donor group was only 53% and 15% of patients in the no-donor group actually received alloSCT. Therefore, 'cross-over' effects lowered the power of donor-versus-no-donor analysis. In the multivariable as-treated analysis including patients from AML96 and AML 2003, OS and RFS of patients with alloSCT were significantly longer (OS: HR 0.58, 95%CI, 0.37 to 0.9, p=.02, RFS: 0.51, 95%CI, 0.34 to 0.76, p=0.001) compared to the PRT group. The probability of OS at 5 years from initiation of consolidation treatment (alloSCT vs. PRT) was 66% (95%CI, 57% to 76%) for patients who received alloSCT compared to 46% (95%CI, 38% to 55%) for PRT patients. The probability of RFS at 5 years from initiation of consolidation treatment was 55% (95%CI, 46% to 67%) for alloSCT patients and 31% (95%CI, 24% to 39%) for PRT patients. Conclusions: Due to cross-over effects which limit the power of the donor-versus-no-donor analysis we give more weight to the results of the as-treated analysis. This analysis suggests that eligible intermediate-risk AML patients with NPM1 wt and absent FLT3-ITD benefit from alloSCT in CR1. However, bias introduced by selection and confounding factors cannot be excluded for this type of analysis and could only be circumvented in randomized controlled trials. Disclosures Thiede: AgenDix: Employment, Other: Ownership. Rösler:Janssen: Consultancy, Other: Travel/Accommodation/Expenses. Middeke:Sanofi: Honoraria. Schetelig:Sanofi: Honoraria.