Measurable Residual Disease Status Research Articles

Conditioning intensity and peritransplant flow cytometric MRD dynamics in adult AML

AbstractIn acute myeloid leukemia (AML), measurable residual disease (MRD) before or after allogeneic hematopoietic cell transplantation (HCT) is an established independent indicator of poor outcome. To address how peri-HCT MRD dynamics could refine risk assessment across different conditioning intensities, we analyzed 810 adults transplanted in first or second remission after myeloablative conditioning (MAC; n = 515) or non-MAC (n = 295) who underwent multiparameter flow cytometry–based MRD testing before as well as 20 to 40 days after allografting. Patients without pre- and post-HCT MRD (MRDneg/MRDneg) had the lowest risks of relapse and highest relapse-free survival (RFS) and overall survival (OS). Relative to those patients, outcomes for MRDpos/MRDpos and MRDneg/MRDpos patients were poor regardless of conditioning intensity. Outcomes for MRDpos/MRDneg patients were intermediate. Among 161 patients with MRD before HCT, MRD was cleared more commonly with a MAC (85 of 104; 81.7%) than non-MAC (33 of 57; 57.9%) regimen (P = .002). Although non-MAC regimens were less likely to clear MRD, if they did, the impact on outcome was greater. Thus, there was a significant interaction between conditioning intensity and “MRD conversion” for relapse (P = .020), RFS (P = .002), and OS (P = .001). Similar findings were obtained in the subset of 590 patients receiving HLA-matched allografts. C-statistic values were higher (indicating higher predictive accuracy) for peri-HCT MRD dynamics compared with the isolated use of pre-HCT MRD status or post-HCT MRD status for prediction of relapse, RFS, and OS. Across conditioning intensities, peri-HCT MRD dynamics improve risk assessment over isolated pre- or post-HCT MRD assessments in patients with AML.

Oral azacitidine prolongs survival of patients with AML in remission independently of measurable residual disease status

AbstractMeasurable residual disease (MRD) in patients with acute myeloid leukemia (AML) in remission after intensive chemotherapy is predictive of early relapse and poor survival. Postremission maintenance therapy that prolongs MRD negativity or converts MRD+ patients to MRD− status may delay or prevent relapse and improve overall survival (OS). In the phase 3 QUAZAR AML-001 trial, oral azacitidine (oral-AZA; formerly CC-486), a hypomethylating agent, significantly prolonged OS and relapse-free survival (RFS) compared with placebo in patients aged ≥55 years with AML in first remission after intensive chemotherapy who were not candidates for hematopoietic stem cell transplantation. In this trial, MRD (≥0.1% leukemic cells in bone marrow) was assessed by multiparameter flow cytometry in serial samples collected at baseline and on day 1 of every 3 cycles. As expected, baseline MRD status was significantly associated with both OS and RFS. Multivariate analyses showed oral-AZA significantly improved OS and RFS vs placebo independent of baseline MRD status. Oral-AZA treatment also extended the duration of MRD negativity by 6 months vs placebo and resulted in a higher rate of conversion from MRD+ at baseline to MRD− during treatment: 37% vs 19%, respectively. In the oral-AZA arm, 24% of MRD responders achieved MRD negativity >6 months after treatment initiation. Although presence or absence of MRD was a strong prognostic indicator of OS and RFS, there were added survival benefits with oral-AZA maintenance therapy compared with placebo, independent of patients' MRD status at baseline. Registered at clinicaltrials.gov as #NCT01757535.

The Current Understanding of and Treatment Paradigm for Newly-Diagnosed TP53-Mutated Acute Myeloid Leukemia

About 10% of newly diagnosed and 20–30% of therapy-related acute myeloid leukemia (AML) harbors a TP53 mutation (mTP53-AML). Unfortunately, this biological subset predicts one of the worst prognoses among patients with AML, specifically a median overall survival of about 7 months with fewer than 10% of patients eventually cured of disease. Although remission rates appear to be increased with venetoclax-based, less-intensive regimens when compared with contemporary, intensive chemotherapy (55–65% vs. 40%), survival appears to be no different between the two approaches. Attempts to discern whether or not the prognosis of mTP53-AML is universally poor have centered around the study of concurrent cytogenetic risk and predicted TP53 allelic state, measurable residual disease status and the impact of conditioning intensity for patients proceeding to allogeneic hematopoietic stem cell transplantation. We discuss these considerations in this review and offer the current treatment approach to TP53-mutated AML.

A Machine Learning Model Based on Tumor and Immune Biomarkers to Predict Undetectable Measurable Residual Disease (MRD) in Transplant-Eligible Multiple Myeloma (MM)

A Machine Learning Model Based on Tumor and Immune Biomarkers to Predict Undetectable Measurable Residual Disease (MRD) in Transplant-Eligible Multiple Myeloma (MM)

Prognostic Impact of NPM1 and FLT3 Mutations at Diagnosis and Presence of Measurable Residual Disease (MRD) after Intensive Chemotherapy (IC) for Patients with Acute Myeloid Leukemia (AML) in Remission: Outcomes from the QUAZAR AML-001 Trial of Oral Azacitidine (Oral-AZA) Maintenance

Prognostic Impact of NPM1 and FLT3 Mutations at Diagnosis and Presence of Measurable Residual Disease (MRD) after Intensive Chemotherapy (IC) for Patients with Acute Myeloid Leukemia (AML) in Remission: Outcomes from the QUAZAR AML-001 Trial of Oral Azacitidine (Oral-AZA) Maintenance

Differential Prognostic Relevance of Measurable Residual Disease in Acute Myeloid Leukemia Patients Undergoing Allogeneic Hematopoietic Stem Cell Transplantation in First Versus Second Morphologic Remission

Introduction: Allogeneic stem cell transplantation (HSCT) offers still the best chance for relapse-free long-term survival for most patients (pts) with acute myeloid leukemia (AML). Allogeneic HSCT may be performed as first line consolidation or following first relapse. Evaluation of measurable residual disease (MRD) at the time of HSCT allows for risk stratification apart from genetic risk at diagnosis. Outcomes of pts transplanted in first vs. second complete remission (CR) or CR with incomplete recovery (CRi) have not been assessed in the context of MRD status at HSCT.Methods: We analyzed 580 AML pts consolidated by allogeneic peripheral blood HSCT at a median age of 60 (range 16-77) years in either first (79%) or second (21%) complete remission (CR) or CR with incomplete peripheral recovery (CRi). Conditioning regimens were non-myeloablative (66%), reduced-intensity (6%) or myeloablative (28%) according to EBMT guidelines. At diagnosis, cytogenetics, and the mutation status of CEBPA, NPM1 and presence of FLT3-ITD were assessed. Using a next-generation targeted amplicon sequencing approach we analyzed a panel comprising 54 recurrently mutated genes in myeloid malignancies on the MiSeq platform (Illumina). In pts with adequate material available (n=300), MRD status at HSCT based on NPM1 mutations , BAALC, MN1, and WT1 expression were evaluated and interpreted as published previously (Lange 2010, Jentzsch 2017 & 2019, Bill 2018). MRD pos pts were defined by being positive for any of the analyzed markers. Median follow up after HSCT was 3.9years.Results: Compared to pts transplanted in first CR/CRi, pts in second CR/CRi were less likely to have a secondary AML (P=.002). They less frequently had a monosomal (P<.002) or complex (P<.001) karyotype, but were more likely to have a normal karyotype (P<.001), to be NPM1 mutated (P=.001), to be biallelic CEBPA mutated by trend (P=.09), and to harbor a FLT3-ITD (P=.04). Pts in second CR/CRi received significantly less chemotherapy prior to HSCT (relapse to HSCT, 71%, 26%, and 3% of pts received 1, 2, or 3 or more cycles, respectively) than pts in first CR/CRi (diagnosis to HSCT, 16%, 61%, and 23% of pts received 1, 2, or 3 or more cycles, respectively, P<.001). Pts transplanted in second CR/CRi tended to more often be MRD pos (P=.10) and had a significantly higher cumulative incidence of relapse (CIR, P<.001, Figure 1A) and significantly shorter event-free survival (EFS, P=.002, Figure 1B) than pts transplanted in first CR/CRi. The MRD status at HSCT was an important prognostic factor in both pts transplanted in first (CIR, P<.001 and EFS, P=.002) and second CR/CRi (CIR, P<.001 and EFS, P=.04, Figure 1C,D). Similar results were obtained when we analyzed the four MRD markers separately. Noteworthy, MRD pos pts transplanted in first CR/CRi and MRD neg pts transplanted in second CR/CRi had similar CIR (P=.42) and EFS (P=.70), which again reflects the worse outcomes of AML pts transplanted in second compared to first CR/CRi as well as the prognostic significance of MRD assessment irrespective of the adapted markers.In the clinically highly relevant group of ELN intermediate risk AML pts where the optimal consolidation (chemotherapy vs. allogeneic HSCT) remains a matter of debate, both MRD neg pts transplanted in in first or second CR/CRi had favorable outcomes (at three years, CIR 15% and 13%, respectively, and EFS, 64% and 63%, respectively), while outcomes were intermediate in MRD pos pts transplanted in first CR/CRi (at 3 years, CIR 38%, and EFS 46%) and very dismal in MRD pos pts transplanted in second CR/CRi (at 3 years, CIR 86%, and EFS 14%).Conclusion: Despite pts transplanted in second CR/CRi had better disease risk at diagnosis, including a lower incidence of monosomal or complex karyotypes, secondary AML and a higher incidence of NPM1 mutations, they had a higher CIR and shorter OS than pts transplanted in first CR/CRi. While the MRD status at HSCT remained an important risk factor independently of the number of remission, MRD pos pts transplanted in first CR/CRi had comparable outcomes as MRD neg pts transplanted in second CR/CRi. The adverse outcomes of MRD pos patients and pts transplanted in second CR/CRi should be taken into account when planning consolidation treatment in AML pts. Benefit of additional therapies prior to HSCT should be evaluated to improve outcomes of eligible MRD pos AML pts, especially when transplanted in second CR/CRi. [Display omitted] DisclosuresJentzsch: Astellas: Honoraria; Jazz Pharmaceuticals: Honoraria; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Backhaus: Bayer: Other: Current Employment of Family Member. Franke: Novartis: Honoraria; MSD: Honoraria; Jazz Pharmaceuticals: Honoraria, Other: Travel Sponsoring; Gilead: Honoraria, Other: Travel Sponsoring; BMS: Honoraria; Pfizer: Honoraria. Vucinic: Novartis: Honoraria; Janssen: Honoraria, Other: Travel Sponsoring; Abbvie: Honoraria, Other: Travel Sponsoring; Gilead: Honoraria, Other: Travel Sponsoring; MSD: Honoraria. Platzbecker: Geron: Honoraria; Novartis: Honoraria; Takeda: Honoraria; AbbVie: Honoraria; Janssen: Honoraria; Celgene/BMS: Honoraria. Schwind: Novartis: Honoraria, Research Funding; Pfizer: Honoraria.

Awareness, Knowledge, and Preferences of United States (US) Patients with Chronic Lymphocytic Leukemia (CLL) and Their Caregivers Related to Finite Duration (FD) Therapy and Minimal (Measurable) Residual Disease (MRD)

Awareness, Knowledge, and Preferences of United States (US) Patients with Chronic Lymphocytic Leukemia (CLL) and Their Caregivers Related to Finite Duration (FD) Therapy and Minimal (Measurable) Residual Disease (MRD)

Negative MRD at Day 100 after Allogenic Hematopoietic Stem Cell Transplant (HSCT): The Grail to Reach in Acute Myeloid Leukemia (AML)

INTRODUCTIONHSCT remains the best curative treatment in eligible AML patients with adverse or intermediate cytogenetics according to the ELN classification, and for those with unfavorable molecular markers at diagnostic or with a positive measurable residual disease (MRD) after intensive chemotherapy. MRD-positivity after HSCT confers an inferior outcome and a recently published study demonstrated that the evaluation of WT1 MRD before HSCT or 3 months after HSCT is highly predictive of post-transplant relapse. Besides, the impact and the kinetics of MRD positivity on prognosis are still unclear. Here we assess the impact of both pre- and post-transplant MRD on long term survival and incidence of relapse among a real-life cohort of 117 AML patients who underwent HSCT. PATIENTS AND METHODFrom November 7, 2012 to December 17, 2019, 117 patients diagnosed with AML and aged over 18 years underwent HSCT in Amiens University Hospital Center. MRD status was assessed using RQ-PCR (sensitivity 10 -4 to 10 -5) or multiparametric flow cytometry (sensitivity 10 -3 to 10 -4) before HSCT, depending on the markers available at diagnosis, at day 30, day 100 and a year after HSCT. Overall survival (OS) and cumulative incidence of relapse (CIR) were evaluated at the same time-points in landmark analysis for patients surviving beyond d100 to reduce the impact of early death on CIR. Statistical analyses were performed with SPSS Statistics 20 (IBM). RESULTSMedian age was 55 years (range 18-72) with 67/117 males. 85% patients had de novo AML. Cytogenetic ELN risk stratification was favorable for 15 (13%), intermediate for 72 (62%) and adverse for 28 (25%). At the time of HSCT, 76% were in complete remission (CR) after intensive chemotherapy. 30 patients (25%) had myeloablative conditioning (MAC) or toxicities-reduced regimens (TRC), 34 patients (30%) had reduced-intensity regimens (RIC) and 53 patients (45%) underwent sequential-based conditioning regimens (Seq). For the 100 patients who survived beyond d100, median time follow-up was 23.5 months (3.0-85.0). OS at 1 and 3 years was respectively 80% (75.9-84.1) and 61.7% (56.1-67.3) and CIR at same time-points was 19,3% (15.2-23.4) and 29,8% (24.6-35.0). No OS and CIR differences were observed according to the conditioning regimen, stem cell source and ELN score. A progressive disease before HSCT increased the risk of relapse but didn't worsen the OS. Before HSCT, MRD was positive in 48 patients (58.5%) with analyzable markers, either at molecular or flow cytometry level. OS and CIR were not impacted by the pre-HSCT MRD. Strikingly, performing HSCT resulted in MRD negativation at day 100 for 85.4% of patients with previous positive MRD, significantly improving OS and CIR (p<.001 for both, Figure 1A and B). Beyond day 100, achieving a negative MRD limited the 5-year CIR to 20%. In multivariate analysis, OS was significantly inferior, in patients with acute GVHD > grade 2 (HR=5.4, 95CI=1.8-16.1; p=.002) and positive MRD at day 100 (HR=19.2, 95CI=6.0-61.1; p<.001). Positive MRD at day 100 was the only significant predictor of adverse CIR (HR=17.5, 95CI=5.6-55.3; p<.001).DISCUSSION/CONCLUSIONIn this real-life cohort of patients diagnosed with AML, we show that HSCT procedure consistently allows MRD negativation, subsequently improving the outcome of patients surviving beyond d100. Persistence of positive MRD after HSCT was the main predictor of long-term adverse outcome after transplant. Our data highlight the importance of MRD negativation at day 100 regardless of pre-transplant status, conditioning regimen or initial ELN classification. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Post-Transplant MRD Status and T Cell Chimerism Predict Outcomes in Patients Allografted for AML/MDS-a Prospective Analysis from the UK NCRI Figaro Trial

▪Allogeneic stem-cell transplantation is an important curative strategy in acute myeloid leukaemia (AML) consequent upon the development of a graft-versus-leukaemia (GVL) effect. Disease relapse is the major cause of transplant failure and novel therapeutic strategies are required in patients with measurable residual disease (MRD) post-transplant. Recognizing that full donor T cell chimerism serves as a biomarker of GVL and that mixed donor T cell chimerism reflects the presence of bi-directional tolerance, we report the first prospective correlation of the impact of post-transplant T cell chimerism and MRD in patients allografted for AML/MDS.Methods: 186 patients from FIGARO, a prospective randomized trial of reduced intensity conditioning regimens in AML/MDS, were alive and relapse free, at the first MRD timepoint and provided post-transplant bone marrow samples for flow cytometric MRD monitoring (day+42, month+3/+6/+9/+12) and peripheral blood samples for T cell chimerism analysis (3-monthly during the first year). Results were not available to clinicians. Flow cytometric MRD incorporating an unsupervised immunophenotypic analysis approach was used on 778 sequential samples. The prognostic significance of post-transplant MRD from each sampling timepoint was assessed by landmark analysis.Results: 29 (15.6%) patients were MRD+ at one or more timepoints in the first year after transplant. The presence of post-transplant MRD was associated with reduced OS (HR:2.19, p=0.0026) and RFS (HR:5.36, p<0.0001), when analyzed as a time varying Cox variable. We, and others, have shown that pre-transplant MRD status is an important determinant of post-transplant survival. We therefore performed a multivariate analysis of factors that may determine the prognoses of patients with pre-transplant MRD+ disease. This demonstrated that the presence of detectable post-transplant MRD was the only independent determinant of RFS in this group of patients (HR 9.05 (95%CI:1.70-48.2), p=0.0099), even when adjusted for cytogenetics, FLT3-ITD and GVHD. The highest frequency of post-transplant MRD positivity occurred at day+42/month+3. The 2yr OS of day+42 MRD+ patients (n=13/158) was 30.8% (95%CI 9.5-55.4) compared to 67.1% (95%CI 58.5-74.2) in MRD negative patients (p<0.001); and 2yr CIR in day+42 MRD+ patients was 92.3% (95% CI:35.8-99.4) versus 22.8%% (95%CI:16.3-29.9) when MRD negative (p<0.001). Day+42 MRD was associated with more rapid relapse kinetics (median RFS of 2 months) compared to when MRD was first detected at later timepoints.Next, we examined the impact of T-cell chimerism, and post-transplant MRD on outcomes. In patients with mixed-donor T-cell chimerism (MDTC) at month+3 or +6, the presence of post-transplant MRD (preceding or at time of first MDTC) was associated with decreased OS (p=0.001) and RFS. Specifically, 2yr RFS in MRD+ patients was 23.1% (95%CI:5.6-47.5), compared to 63.6% (95%CI:44.9-77.5) in patients who were MRD negative (p=0.004) (Figure). In contrast, in 48 patients with full donor T-cell chimerism (FDTC) at months 3 and 6, only 5 patients were MRD+ post-transplant and their outcomes were equivalent to patients who were MRD negative (FDTC/MRD negative 2yr RFS: 80.9% (95% CI:65.3-90.0)).Downregulation of HLA class II molecules on AML blasts after transplant may result in immune evasion from GVL: we examined whether this had an additional impact on outcome in post-transplant MRD+ patients. Both RFS and OS were significantly lower in MRD+ patients when MRD+ blasts had down-regulated HLA-DR expression. In MRD+ patients, 2yr OS was 20.0% (95%CI:3.1-47.5) in those with HLA-DR down-regulation, versus 57.9% (95%CI 33.2-76.3) in those without (p=0.001).Conclusion We demonstrate that dynamic assessment of post-transplant MRD is an important predictor of outcome in patients allografted for AML/MDS, with additional prognostic value to pre-transplant MRD assessment. Post-transplant MRD and T-cell chimerism results are most informative when combined, underlining the importance of a GVL effect in AML/MDS. This suggests post-transplant strategies which result in FDTC may improve outcomes in patients allografted for AML/MDS. Our data also supports the clinical relevance of monitoring for leukemic immune escape as HLA-DR down-regulation identifies a post-transplant MRD positive subgroup at risk of almost inevitable relapse. [Display omitted] DisclosuresLoke: Novartis: Other: Travel; Janssen: Honoraria; Amgen: Honoraria; Pfizer: Honoraria; Daichi Sankyo: Other: Travel. Protheroe: Jazz Pharmaceuticals: Honoraria; Astellas: Honoraria; Kite Gilead: Honoraria. Dillon: Amgen: Other: Research support (paid to institution); Astellas: Consultancy, Other: Educational Events , Speakers Bureau; Jazz: Other: Education events; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: educational events; Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Session chair (paid to institution), Speakers Bureau; Menarini: Membership on an entity's Board of Directors or advisory committees; Shattuck Labs: Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Research Support, Educational Events. Craddock: Novartis Pharmaceuticals: Other: Advisory Board ; Celgene/BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Treatment with an Allogeneic Leukemia-Derived Dendritic Cell Vaccine in AML Patients Shows MRD Conversion and Improved Survival

Treatment with an Allogeneic Leukemia-Derived Dendritic Cell Vaccine in AML Patients Shows MRD Conversion and Improved Survival

Prompt CR Plus Consolidation Therapy Yields Improve Survival after Allogeneic Transplantation for AML Patients Receiving Myeloablative, but Not Reduced-Intensity Conditioning: A CIBMTR Analysis

▪Leukemia relapse and treatment related mortality (TRM) remain major obstacles for successful allogeneic hematopoietic cell transplantation (allo-HCT). The number of induction cycles using intensive chemotherapy at AML diagnosis to achieve complete remission (CR) and the number of consolidation cycles and disease status at the time of allo-HCT for patients with acute myeloid leukemia (AML) may each affect TRM and relapse rates. We investigated the impact of the number of induction/consolidation cycles and disease status on the success of allo-HCT in 3113 AML patients reported to the Center for International Blood and Marrow Transplant Research (CIBMTR) (2008-2019). They received allo-HCT in first CR or with persistent leukemia (primary induction failure-PIF) receiving myeloablative (MA) or reduced-intensity (RIC) conditioning.1473 AML patients (median age, 47 years) in CR received MAC; 862 (58%) achieved CR after 1 cycle of intensive induction chemotherapy and 74% of these had no evidence of measurable residual disease (MRD). 454 (31%) patients required 2 cycles to CR (72 % MRD negative) and 157 (11%) patients (69% MRD negative) after ≥ 3 cycles. The overall survival (OS), relapse and TRM by induction cycle number is shown in Table 1. Multivariate analysis demonstrated that CR after 1 cycle led to higher OS vs. 2 cycles (HR 1.32 95%CI 1.11-1.56, p< 0.01) or ≥ 3 cycles (HR 1.47 95%CI 1.16-1.87, p< 0.01), while OS after 2 cycles or ≥ 3 cycles were similar (HR 1.2 95%CI 0.87-1.4, p=0.38). Higher TRM was observed in patients receiving 2 or ≥ 3 cycles vs. only 1 induction cycles (HR 1.34 95%CI 1.05-1.72, p< 0.02). Relapse risk was greater in those needing ≥ 3 cycles to achieve CR. Consolidation therapy after CR was associated with improved OS vs. no consolidation therapy (HR 1.57 95%CI 1.24-1.99, p< 0.01). The need for ≥2 induction cycles plus consolidation therapy was associated with higher TRM (HR 1.34 95%CI 1.05-1.72, p< 0.02). 1162 AML patients (median age, 63 years) in CR received allo-HCT after RIC; 714 (61%) achieved CR after 1 cycle of induction chemotherapy (72% MRD negative); 310 (27%) patients after 2 cycles (67% MRD negative) and 138 (12%) patients (58% MRD negative) after ≥ 3 cycles (Table 1). Multivariate analysis demonstrated that the number of induction cycles did not affect the OS or TRM. Relapse risk was greater in patients requiring ≥2 cycles to achieve CR. The use of consolidation therapy did not affect OS or TRM. MRD status at the time of allo-HCT did not have a significant impact on OS, TRM and relapse rates after either MA or RIC conditioning.478 AML patients received allo-HCT after PIF (328 patients with MAC [median age, 51 years], 150 patients RIC [median age, 61 years], Table 1). After MAC, OS and relapse were significantly worse in PIF patients compared to any CR patients (p<0.01). After RIC, relapse was significantly more frequent in PIF patients vs. CR patients after 1 or more induction cycles (p<0.01). TRM was similar for PIF vs CR patients after MAC or RIC allo-HCT.These data demonstrate that among patients eligible for allo-HCT, the need for only one induction cycle to achieve CR, particularly when combined with consolidation therapy is associated with better outcomes after MA conditioning. Achieving CR prior to allo-HCT needing one or more induction cycles is associated with lower relapse rates and improved OS compared to patients with PIF that receive allo-HCT. [Display omitted] Disclosuresde Lima: BMS: Membership on an entity's Board of Directors or advisory committees; Incyte: Membership on an entity's Board of Directors or advisory committees; Miltenyi Biotec: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees. Hourigan: Govt. COI: Other. Litzow: Omeros: Other: Advisory Board; Pluristem: Research Funding; Jazz: Other: Advisory Board; AbbVie: Research Funding; Amgen: Research Funding; Actinium: Research Funding; Astellas: Research Funding; Biosight: Other: Data monitoring committee. Saber: Govt. COI: Other. Weisdorf: Incyte: Research Funding; Fate Therapeutics: Research Funding.

Measurable Residual Disease Status and FLT3 Inhibitor Therapy in Patients with FLT3-ITD Mutated AML Following Allogeneic Hematopoietic Cell Transplantation

BACKGROUNDMeasurable residual disease (MRD) is associated with increased risk of relapse and death in acute myeloid leukemia (AML), even after allogeneic hematopoietic cell transplantation (HCT). Recently, next-generation sequencing (NGS) has emerged as a sensitive and specific method to detect MRD from both bone marrow and peripheral blood. NGS methods are particularly useful for detecting internal tandem duplication mutations of the FMS-like tyrosine kinase 3 gene (FLT3-ITD), which define a subgroup of AML patients who may be at higher risk for relapse and who often undergo consolidative allogeneic HCT. The SORMAIN trial recently reported a highly significant relapse-free survival benefit for the first generation FLT3 inhibitor sorafenib as post-HCT maintenance, particularly among patients with detectable MRD following HCT.In 2019 our program initiated prospective FLT3-ITD monitoring by NGS using a commercially available assay (Invivoscribe, Inc., San Diego, CA) of the peripheral blood or bone marrow throughout the first three months following HCT for all patients with FLT3-ITD mutated AML undergoing HCT. We encouraged but did not mandate FLT3 inhibitor use, regardless of MRD status. In this study, we describe the clinical impact of sensitive FLT3 MRD testing early after HCT, maintenance FLT3 inhibitor use in a non-clinical trial setting, and the ability of early post-HCT FLT3 inhibitor therapy to modify transplant outcomes. RESULTSThirty-six adults with FLT3-ITD mutated AML underwent HCT at Stanford University between April 2019 and August 2020 and were included in this observational study (Table 1). These patients were not enrolled in clinical trials evaluating FLT3 inhibitor therapy after HCT. Twenty-nine (81%) received pre-HCT FLT3 inhibitors, and 78% were in first complete remission (CR1) at HCT. Median follow up after HCT was 14.0 months (range 4.6-25.7). Two patients were excluded from subsequent analyses due to early graft failure and receipt of azacitadine/enasidenib maintenance, respectively. Of the evaluable cohort, 9 (26%) experienced clinical relapse at a median of 4.2 months after HCT (range 1.8-6.1), and 10 (29%) died, 5 from transplant-related mortality and 5 from AML (Figure 1A and B).Of the 34 patients evaluable for post-HCT MRD analysis, 10 (29%) had detectable MRD within the first three months while 24 (71%) remained MRD-negative (Figure 2A and B). Although there was a trend towards inferior progression-free survival (PFS) for patients with early post-HCT MRD (p = 0.13, Figure 3A), OS was not significantly impacted by MRD (p = 0.35, Figure 3B). Among the four patients with early post-HCT MRD negativity who ultimately relapsed, only one was FLT3-negative at time of relapse.Twenty-four patients (71%) received FLT3 inhibitor maintenance, initiated a median of 2.8 months after transplant (range 0.7-17.1), and the median duration was 10.6 months (range 1.7-23.7). The most common FLT3 inhibitor used was gilteritinib (n = 15), followed by midostaurin (n = 9), and sorafenib (n = 5). Among the 10 patients (29%) who did not receive post-transplant maintenance, reasons included graft-versus-host disease (GVHD) (n = 4), clinician decision (n = 3), cytopenias (n = 2), and thrombotic microangiopathy (n = 1). The use of maintenance FLT3 inhibitors led to a significantly superior PFS and OS (Figure 3C and D). Interestingly, the use of early FLT3 inhibitors post-HCT augmented PFS and OS in both MRD-negative and MRD-positive patients (Figure 3E and F), and effectively prevented clinical relapse in four patients with post-HCT MRD positivity (Figure 2A). CONCLUSIONIn this cohort study, we evaluated the clinical utility of sensitive post-transplant MRD monitoring and maintenance FLT3 inhibitors on transplant outcomes. We demonstrate that clinical relapse can be prevented even in patients with post-HCT MRD through the incorporation of early FLT3 inhibitors. This finding is in keeping with the results from the SORMAIN trial. We also found that real-time sensitive MRD results allowed clinicians to begin early initiation of FLT3 inhibitor therapy, which positively affected outcomes. [Display omitted] DisclosuresMannis: AbbVie, Agios, Astellas Pharma, Bristol Myers Squibb, Genentech, MacroGenics, Pfizer, and Stemline: Consultancy; Astex, Forty Seven Inc/Gilead, Glycomimetics, and Jazz Pharmaceuticals: Research Funding. Muffly: Adaptive: Honoraria, Other: fees for non-CME/CE services: , Research Funding; Astellas, Jasper, Adaptive, Baxalta: Research Funding; Pfizer, Amgen, Jazz, Medexus, Pfizer: Consultancy.

Maintenance Therapy in Patients with FLT3-ITD-Mutation-Positive Acute Myeloid Leukemia after Allogeneic Hematopoietic Cell Transplantation: Real-World Survival

▪Background: Patients with FLT3-mutation-positive (FLT3mut+) acute myeloid leukemia (AML) have a poor prognosis, particularly those with a high allelic burden of FLT3-ITD mutations (FLT3-ITD mut+). Further, patients with FLT3-ITD mut+ who have relapsed after allogeneic hematopoietic stem cell transplantation (HSCT) have a 1-year overall survival (OS) rate of less than 20%. While treatment guidelines vary in their recommendations for maintenance therapy after HSCT to prevent relapse, data are emerging on the potential benefits of maintenance therapy for patients with FLT3mut+ AML.Aim/Objective: To examine real-world survival outcomes in adult patients with FLT3-ITD mut+ AML who received maintenance therapy versus those who did not receive maintenance therapy after allogeneic HSCT, including a qualitative comparison with real-world survival outcomes in adults with FLT3mut+ AML.Methods: This was a retrospective chart review wherein hematologists and oncologists from North America, Europe, and Japan extracted data from the medical charts of patients with FLT3mut+ AML who underwent HSCT after achieving complete remission with first-line chemotherapy within the prior 3 years. The index date was the date of HSCT and the study period was from the index date to the date of the last follow-up or death. All patients were grouped into two cohorts based on post-HSCT therapy received (no maintenance therapy or maintenance therapy). In an analysis of a subgroup of patients typically considered to be at high risk of relapse, patients who had both received an allogeneic HSCT and had a high allelic burden of FLT3-ITD mut+ were analyzed; patients with FLT3-ITD and FLT3-TKD co-mutations were also included in this subgroup. Overall survival during the study period was assessed for each cohort in the overall population of patients and in the subgroup. Kaplan-Meier analyses and Cox regression models, including unadjusted models and models with adjustments for baseline covariates, were used to describe and evaluate cross-cohort comparisons of survival. Covariates in the adjusted Cox models were Eastern Cooperative Oncology Group status, risk status, measurable residual disease status, age at index date, sex, extramedullary involvement, race, BMI, time from diagnosis to index month, HSCT type, and country.Results: A total of 1,208 AML patients with FLT3mut+ who received HSCT were included in the general study population; 765 (63.3%) patients received no maintenance therapy and 443 (36.7%) patients received maintenance therapy (including FLT3 inhibitors, hypomethylating agents, cytotoxic chemotherapy, and other targeted therapies). In Kaplan-Meier analyses, OS was longer in patients who received maintenance therapy compared with those who did not receive maintenance therapy (log-rank P<0.001; Figure A). Similar results were seen between maintenance therapy versus no maintenance therapy in an unadjusted Cox regression model (HR 0.52 [95% CI 0.35, 0.76], P<0.001) and adjusted Cox regression model (HR 0.48 [95% CI 0.30, 0.77], P<0.01).In an analysis of the subgroup, data from the charts of 745 patients with FLT3-ITD mut+ who received allogeneic HSCT were reviewed. The mean age at HSCT was 53.2 years; 39.9% and 38.4% of patients had intermediate and poor risk status, respectively. Of this subgroup, 473 (63.5%) patients received no maintenance therapy and 272 (36.5%) patients received maintenance therapy. Kaplan-Meier analyses show that OS was longer in patients receiving maintenance therapy versus no maintenance therapy (log-rank P<0.001; Figure B); the risk of death appeared to plateau after approximately 2 years in patients receiving maintenance treatments. Similar results were seen between maintenance therapy versus no maintenance therapy in an unadjusted Cox regression model (HR 0.39 [95% CI 0.23, 0.65], P<0.001) and adjusted Cox regression model (HR 0.38 [95% CI 0.20, 0.72], P<0.01).Conclusions: In patients with FLT3-ITD mut+ AML, OS was improved in patients that received any type of maintenance therapy compared with patients that received no maintenance therapy after allogeneic HSCT. These improved clinical outcomes in a high-risk subgroup receiving maintenance treatments are consistent with findings in the general population of patients with FLT3mut+ AML. Additional analyses are warranted to statistically verify these results. [Display omitted] DisclosuresYang: Astellas Pharma, Inc.: Consultancy. Song: Astellas Pharma, Inc.: Consultancy. Griffin: Astellas Pharma, Inc.: Consultancy; Novartis: Patents & Royalties: Post marketing royalties from midostaurin. Shah: Astellas Pharma, Inc.: Current Employment; University of Michigan School of Public Health Department of Health Management and Policy Alumni Board: Other: Chair-Elect. Freimark: Astellas Pharma, Inc.: Consultancy. Chilelli: Astellas Pharma, Inc.: Current Employment.

The Impact of CD19 Expression Combined with Measurable Residual Disease on Post-Remission Treatment and Outcome in Adult t(8;21) Acute Myeloid Leukemia

Background: Acute myeloid leukemia (AML) with t(8;21) has considerable clinical heterogeneity. Only 50% of these patients receiving multiple cycles of high-dose cytarabine as post-remission treatments could achieve long term survival, and relapse occures in up to 40% of them. Therefore, further risk stratification is needed to guide appropriate post-remission treatment for t(8;21) AML patitents in first complete remission(CR1). Measurable residual disease (MRD) monitored by RUNX1-RUNX1T1 transcript levels after treatment is established as a powerful marker to predict relapse and guide treatment. Recent studies revealed cell-surface antigen CD19 negativity (CD19-) was a risk factor for relapse in t(8;21) AML. However, reports about the impact of CD19 expression combined with RUNX1-RUNX1T1 MRD on post-remission treatment remains absent to date.Methods: A total of 155 consecutive patients diagnosed with t(8;21) AML were enrolled in this study, including 69 patients who received chemotherapy (CMT) and 86 who received allogeneic stem cell transplantation (allo-SCT) as post remission treatment in CR1. MRD+ was defined as a < 3 log reduction of RUNX1/RUNX1T1 level after the second consolidation therapy.Results:With a median follow-up of 40 months (range, 4-133 months), the 3-year OS, LFS and CIR rates were 75.57% ,70.46% and 27.50% for the entire population, respectively. The 3-year CIR was dramatically decreased in allo-SCT than in CMT group (13.47% vs 49.19%, p<0.001). Allo-SCT demonstrated a significantly superior 3-year OS (85.78% vs 58.89%, p< 0.001) and LFS (85.64% vs 45.84%, p< 0.001) over CMT, respectively. The 3-year cumulative incidence of TRM was 9.27% and 7.04% in the CMT and allo-HSCT groups, respectively (p=0.890). KIT exon 17 mutation was a risk factor for OS in multivariate analysis, CD19 negativity was a risk factor for RFS in univariate analysis. Allo-SCT was a beneficial factor for LFS and OS in multivariate analysis when taking CMT as a reference. For CD19- patients (n=59), allo-HSCT demonstrated significantly lower CIR (17.20% vs 51.03%, p=0.006) , better OS (95.24% vs 51.55%, p < 0.001) and LFS (82.8% vs 39.71%, p = 0.001) than CMT. On the other hand, CMT had a comparable CIR (26.70% vs 11.40, p=0.064 ), OS (73.19% vs 86.01%, p=0.153) and LFS (71.58% vs 87.76%, p=0.067) with allo-SCT for CD19+ patients (n=80). Notably, when combined with RUNX1-RUNX1T1 transcripts after the second consolidation, allo-SCT preserved a significantly lower CIR (6.67% vs 66.67%, p=0.002), improved OS (100% vs 33.33%, p< 0.001) and LFS (93.33% vs 33.33%, p=0.001) than CMT in CD19-MRD+ group (n=22), respectively. In contranst, CMT revealed similar OS (80.0% vs 87.5%, p=0.677 ), LFS (60% vs 62.5%, p=0.663) and CIR (40.00% vs 37.50%, p=0.795 ) with allo-SCT in CD19-MRD- patients (n=13), respectively. For CD19+ patients, addition of MRD status had no impact on the outcome of allo-SCT and CMT. CMT preserved comparable OS (75% vs 84.66%, p =0.516), LFS (85.71% vs 96.30%, p =0.357 ) and CIR (12.50% vs 3.70%, p =0.367) with allo-SCT for CD19+MRD+ patients (n=36), and comparable OS (100% vs 92.31%, p =0.459), LFS (83.33% vs 85.29%, p =0.940 ) and CIR (16.67% vs 13.54%, p =0.998) with allo-SCT in CD19+MRD- patients (n=33).Conclusion: Combination of CD19 expression and RUNX1-RUNX1T1 MRD improved risk stratification and treatment guidance for t(8;21) AML in CR1. Allo-SCT might be recommended for the CD19-MRD+ patients, while CMT might be a reasnonable choice for CD19-MRD+ and CD19+ patients. Multicenter prospective studies are warranted to confirm the current results.Key words: t(8;21) AML, CD19, measurable residual disease, post-remission treatment, allo-SCT, chematherapy DisclosuresNo relevant conflicts of interest to declare.

Phase 1b Study of Lower-Dose CPX-351 Plus Venetoclax As First-Line Treatment for Patients with AML Who Are Unfit for Intensive Chemotherapy: Preliminary Safety and Efficacy Results

Phase 1b Study of Lower-Dose CPX-351 Plus Venetoclax As First-Line Treatment for Patients with AML Who Are Unfit for Intensive Chemotherapy: Preliminary Safety and Efficacy Results

Applicability of the Hematopoietic Cell Transplantation Comorbidity Index (HCT-CI) to Predict Outcomes of Acute Myeloid Leukemia Patients Older Than 60 Years Undergoing Non-Myeloablative Allogeneic Stem Cell Transplantation

Background: For most acute myeloid leukemia (AML) patients an allogeneic hematopoietic stem cell transplantation (HSCT) offers the highest chance of cure and long-term survival. Higher age and/or comorbidities may confine this option in a considerable number of AML patients due to toxic myeloablative preparation regimens. Non-myeloablative conditioning (NMA) regimes were developed to allow HSCT in these patients. The HSCT comorbidity index (HCT-CI) has been shown to predict outcome after allogeneic HSCT in cohorts of unselected patients. However, there is no separate evaluation of its prognostic significance in older (> 60 years) AML patients undergoing less-toxic NMA-HSCT. We evaluated the prognostic impact of the HCT-CI in a large, homogenously treated AML patient cohort that received NMA-HSCT.Methods: We retrospectively analyzed 289 AML patients older than 60 years (median age 66, range 60-77 years) at the time of NMA-HSCT. The conditioning regimen consisted of fludarabine 30 mg/m 2 for 3 consecutive days in addition to 2 (n=278) or 3 Gy (n=6) total body irradiation (TBI), five patients received 2 Gy TBI alone. Graft versus host disease prophylaxis contained cyclosporine and mycophenolate mofetil, none of the patients received in vivo or in vitro T-cell depletion. Disease risk at diagnosis was assessed according to the European LeukemiaNet (ELN) 2017 classification. In patients transplanted in morphologic remission, measurable residual disease (MRD) at HSCT was assessed based on NPM1 mutations and BAALC, MN1, and WT1 expression levels. The pre-transplant HCT-CI was calculated prior to the start of the conditioning regimen. Median follow up after HSCT was 3.8 years.Results: 97% of the patients (n=281) engrafted. 36% of the patients (n=104) had a low risk (0 points), 31% (n=90) an intermediate risk (1-2 points), and 33% (n=95) a high risk (≥3 points) HCT-CI score. The performance score at HSCT (ECOG, 0/1 vs. 2/3) was not different between HCT-CI risk groups (P=.86). Incidences of chronic graft-versus-host disease (GvHD) were 16% limited and 52% extensive disease. The non-relapse mortality (NRM) did not differ significantly between HCT-CI risk groups after NMA-HSCT (P=.56, Figure 1A, at 5 years HCT-CI low 24% vs. HCT-CI intermediate 20% vs. HCT-CI high 27%, respectively). Likewise, neither the cumulative incidence of relapse (P=.88, Figure 1B, at 5 years 46% vs. 45% vs. 43%) nor the overall survival (P=.70, Figure 1C, at 5 years 40% vs. 44% vs. 41%) differed according to the HCT-CI risk groups. The HCT-CI also did not impact outcomes in separate analyses according to ELN2017 risk at diagnosis (OS, P=.20, P=.30, and P=.70 for favorable, intermediate, and adverse, respectively) or MRD status prior to HSCT (OS, P=1 and P=.30 for MRD-negative and MRD-positive patients, respectively). In the favorable risk subgroup of patients being MRD-negative at the time of NMA-HSCT, the median overall survival reached 49% at 5 years after NMA-HSCT, irrespective of the HCT-CI.Conclusion: In the here presented cohort of older AML patients a higher HCT-CI did not have a negative impact on NRM or survival. In general, the NRM following NMA-HSCT was relatively low. Our data indicates that comorbidities per se - reflected by a higher HCT-CI score - should not impede NMA-HSCT. Independently from the HCT-CI score MRD-negative patients had notably good survival of 49 % at 5 years following NMA-HSCT. As the incidences of chronic graft-versus host disease were relatively high, alternative immunosuppressive strategies may help to further improve outcomes. Our data aid in informed clinical decisions regarding HSCT consolidation in older AML patients since we show that HSCT with this reduced toxicity regimen represents a feasible treatment option in older and comorbid AML patients also with higher HCT-CI scores. [Display omitted] DisclosuresBackhaus: Bayer: Other: Current Employment of Family Member. Jentzsch: Astellas: Honoraria; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Honoraria. Vucinic: Janssen: Honoraria, Other: Travel Sponsoring; Novartis: Honoraria; Gilead: Honoraria, Other: Travel Sponsoring; Abbvie: Honoraria, Other: Travel Sponsoring; MSD: Honoraria. Franke: BMS: Honoraria; Gilead: Honoraria, Other: Travel Sponsoring; Jazz Pharmaceuticals: Honoraria, Other: Travel Sponsoring; MSD: Honoraria; Novartis: Honoraria; Pfizer: Honoraria. Platzbecker: Celgene/BMS: Honoraria; AbbVie: Honoraria; Janssen: Honoraria; Novartis: Honoraria; Geron: Honoraria; Takeda: Honoraria. Schwind: Novartis: Honoraria, Research Funding; Pfizer: Honoraria.

Autologous hematopoietic cell transplantation during second or subsequent complete remission of acute promyelocytic leukemia: a prognostic factor analysis.

Autologous hematopoietic cell transplantation (HCT) is an effective therapy for patients with relapsed acute promyelocytic leukemia (APL). However, it remains unclear whether this procedure is equally effective for certain groups of patients. To address this question, we analyzed 296 patients with APL who had undergone autologous HCT during second or subsequent complete remission (CR2+) between 2006 and 2019. Among them, 24 patients were ≥65 years old, and 17 underwent autologous HCT during third or subsequent CR. Of the 286 patients whose measurable residual disease (MRD) data were available, 21 showed detectable MRD. The 5-year probabilities of relapse-free survival (RFS), overall survival, relapse, and nonrelapse mortality for the entire cohort were 85%, 88%, 9%, and 6%, respectively. The multivariate analysis revealed that the duration of first CR ( < or ≥2 years) was the sole factor associated with RFS (P = 0.002), but even those with CR1 duration <2 years showed a 5-year RFS of 76%. The other factors such as age, disease status, and MRD status were not predictive for the survival outcomes. Our findings demonstrate very favorable long-term results when autologous HCT is conducted during CR2 + across the various subgroups of patients with relapsed APL.

OAB-056: A machine learning model based on tumor and immune biomarkers to predict undetectable measurable residual disease (MRD) in transplant-eligible multiple myeloma (MM)

<h3>Background</h3> There is expectation of using biomarkers to personalize treatment. Yet, a successful treatment selection cannot be confirmed before 5 or 10 years of progression-free survival (PFS). Treatment individualization based on the probability of an individual patient to achieve undetectable MRD with a singular regimen, could represent a new model towards personalized treatment with fast assessment of its success. This idea has not been investigated previously. <h3>Methods</h3> We sought to define a machine learning model to predict undetectable MRD in newly-diagnosed transplant-eligible MM patients (n=278). The training (n=152) and internal validation cohort (n=60) consisted of 212 active MM patients enrolled in the GEM2012MENOS65 clinical trial. The external validation cohort was defined by 66 high-risk smoldering MM patients enrolled in the GEM-CESAR clinical trial, which treatment differed only by the substitution of bortezomib by carfilzomib during induction and consolidation. Patients were included in the study based on data availability of 17 parameters (p≤.05) associated with MRD outcomes. <h3>Results</h3> We started by investigating patients' MRD status after VRD induction, HDT/ASCT and VRD consolidation (GEM2012MENOS65) according to their ISS and Revised-ISS, LDH levels, and cytogenetic alterations. High LDH levels and del(17p13), two features relatively infrequent at diagnosis, were the only parameters associated with lower rates of undetectable MRD. The ISS and R-ISS were not predictive. Therefore, we aimed to evaluate other disease features associated with MRD outcomes and develop more effective models based on machine learning logistic regression. The most effective one resulted from integrating cytogenetic [t(4;14) and/or del(17p13)], tumor burden (plasma cell clonality in bone marrow and circulating tumor cells in peripheral blood) and immune related (myeloid precursors, mature B cells, intermediate neutrophils, eosinophils, CD27negCD38pos T cells and CD56brightCD27neg NK cells) biomarkers. Data obtained for an individual patient can be substituted into our formula, which results in a numerical probability of achieving undetectable (>0.5) vs persistent (0.685 or <0.365 (observed in 102/212 patients), MRD outcomes are respectively predicted with higher confidence. Standard-confidence, high-confidence, and external validation predictions were accurate in 152/212 (71.7%), 85/102 (83.3%), and 48/66 (72.7%) patients respectively. Patients predicted to achieve undetectable MRD using standard and high-confidence values showed longer PFS and OS than those with probability of persistent MRD. <h3>Conclusions</h3> We demonstrated that selecting a regimen based on probable MRD outcomes, and confirming soon after if that probability was accurate, is a possible new approach towards individualized treatment in MM. The model is available at www.MRDpredictor.com to facilitate its use in clinical practice.

Hypomethylating Agents and FLT3 Inhibitors As Maintenance Treatment for Acute Myeloid Leukemia and Myelodysplastic Syndrome After Allogeneic Hematopoietic Stem Cell Transplantation–A Systematic Review and Meta-Analysis

BackgroundDisease relapse remains the major cause of death among patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) who receive an allogeneic hematopoietic cell transplant (allo-HCT). Maintenance treatment with FLT3 inhibitors and hypomethylating agents (HMA) has been studied in various clinical trials with mixed results. ObjectiveTo synthesize the current evidence on the efficacy and safety of FLT3 inhibitors and HMA for maintenance therapy after allo-HCT in AML and MDS. MethodsFor this systematic review and meta-analysis Cochrane Library, Google Scholar, Ovid Medline, Ovid Embase, PubMed, Scopus, and Web of Science Core Collection were searched from inception to March 2021 for studies on maintenance therapies after allo-HCT in AML and MDS. Studies were excluded if they were reviews, commentaries, case series with <5 patients, or basic research articles, not published in English, not on post-allo-HCT maintenance with FLT3 inhibitors or HMA in AML or MDS, or if they were clinical trials without published results or duplicate publications from the same patient cohort. Studies with insufficient reporting of the primary endpoint (2-year overall survival [OS]) and studies using FLT3 inhibitors or HMA for pre-emptive treatment of imminent relapse based on positive measurable residual disease testing were excluded. Random-effects models were used to pool response rates for the primary outcome of 2-year OS. Hazard ratios (HR) for death and relapse were calculated for studies that included a control group. Rates of relapse-free survival (RFS), non-relapse mortality, and acute and chronic graft-versus-host-disease (GVHD) were studied as secondary endpoints. Downs and Black checklist and risk of bias assessments were used to gauge the quality of individual studies. The study protocol has been registered on PROSPERO (CRD42020187298). ResultsOur search strategy identified 5559 studies. Twenty-one studies with a total of 809 patients were included in the meta-analysis. The 2-year OS rates were 81.7% (95% confidence interval [CI], 73.8%-87.7%) and 65.7% (95% CI, 55.1%-74.9%) among patients treated with FLT3 inhibitors and HMA, respectively. In sensitivity analyses restricted to studies that included a control group, maintenance therapy with FLT3 inhibitors (HR for death = 0.41; 95% CI, 0.26-0.62) or HMA (HR = 0.45; 95% CI, 0.31-0.66) appeared superior to no maintenance therapy. The 2-year RFS rates were 79.8% (95% CI, 75.0%-83.9%) and 62.4% (95% CI, 50.6%-72.9%) among patients treated with FLT3 inhibitors and HMA, respectively. Rates of any grade acute and chronic GVHD were 33.1% (95% CI, 25.4%-41.8%; grade 3/4: 16.5%) and 42.5% (95% CI, 26.3%-60.4%) among FLT3 inhibitor and 42.7% (95% CI, 33.5%-52.4%; grade 3/4: 8.1%) and 41.5% (95% CI, 32.0%-51.6%) among HMA-treated patients, respectively. ConclusionMaintenance therapy with either FLT3 inhibitors or HMA after allo-HCT can lead to prolonged and improved OS and RFS with a favorable safety profile. Additional studies are needed to define the optimal duration of treatment, the role of measurable residual disease status, and transplant characteristics in patient selection.

AML-065: Measurable Residual Disease Status and FLT3 Inhibitor Therapy in Patients with FLT3-ITD-Mutated AML Following Allogeneic Hematopoietic Cell Transplantation

<h3>Context:</h3> In 2019, our transplant program initiated prospective <i>FLT3-ITD</i> measurable residual disease (MRD) monitoring by next-generation sequencing (NGS) of the peripheral blood or bone marrow throughout the first three months following HCT for all patients with FLT3-ITD-mutated AML undergoing HCT. We encouraged FLT3 inhibitor use as post-HCT maintenance. <h3>Objective:</h3> To evaluate the impact of post-HCT FLT3 MRD testing and FLT3 inhibitor use in a non-clinical trial setting. <h3>Design:</h3> Observational study of adults with FLT3-ITD-mutated AML who underwent allogeneic HCT at Stanford University between April 2019 and August 2020. <h3>Setting:</h3> Tertiary referral center. <h3>Patients or Other Participants:</h3> Thirty-six adults with FLT3-ITD-mutated AML are included in this study. Two patients were excluded from analyses due to early graft failure and receipt of azacitidine/enasidenib maintenance therapy. <h3>Interventions:</h3> Twenty-four patients (71%) received an FLT3 inhibitor after HCT, initiated a median of 2.8 months after transplant (range: 0.7–17.1). The median duration was 6.8 months (range: 1.1–18.8). <h3>Main Outcome Measures:</h3> Progression-free survival (PFS) and overall survival (OS). <h3>Results:</h3> Ten patients (29%) had detectable MRD within the first three months following HCT, while 24 (71%) patients remained MRD-negative. Although there was a trend toward inferior PFS for patients with early post-HCT MRD (p = 0.12), OS was not significantly impacted by MRD (p = 0.66). FLT3 inhibitor therapy improved PFS and OS, particularly in MRD-negative patients (maintenance <i>vs</i> no maintenance: PFS not reached <i>vs</i> 5.52 months, p=0.002; OS not reached <i>vs</i> 5.85 months, p=0.006). <h3>Conclusions:</h3> Clinical relapse can be prevented, even in patients with post-HCT MRD, by using early FLT3 inhibitor maintenance therapy, in keeping with the results from the SORMAIN trial. Real-time sensitive MRD testing allows clinicians to begin early initiation of FLT3 inhibitor therapy. This work was partially supported by the National Institutes of Health Grant UL1-TR003142 and Grant P30-CA124435.