Minimal residual disease prior to allogeneic hematopoietic cell transplantation in acute myeloid leukemia: a meta-analysis

Randomized phase 2 study to assess the role of single-agent nivolumab to maintain remission in acute myeloid leukemia

ABSTRACT

We conducted a multicenter, open-label, randomized phase 2 study to assess the efficacy of nivolumab (Nivo) as maintenance therapy for patients with acute myeloid leukemia (AML) in first complete remission (CR) or CR with incomplete hematologic recovery who were not candidates for stem cell transplant. Patients were stratified and randomized to observation (Obs) or Nivo (3 mg/kg IV every 2 weeks for 46 doses). The primary end point was progression-free survival (PFS) defined as time to disease relapse or death due to any reason. Secondary end points included overall survival (OS), and evaluation of adverse events (AEs) after Nivo administration. Eighty patients were enrolled with median duration of follow-up of 24 months (33 months among survivors). PFS was 13.2 months in the Nivo arm and 10.9 months in the Obs arm. Overall PFS curves were not statistically significantly different. The median OS was 53.9 months in the Nivo arm and 30.9 months in the Obs arm. There were more AEs of any type (regardless of attribution) on the Nivo arm; 27 patients (71%) on the Nivo arm had a grade ≥3 AE compared with 5 patients (12%) on the Obs arm (P < .001). Nivo maintenance after AML chemotherapy failed to improve the PFS and OS in this randomized phase 2 study. There were increased AEs and serious AEs (SAEs) with Nivo, but these AEs and SAEs were expected and manageable. This trial was registered at www.ClinicalTrials.gov as #NCT02275533.

Combination of disease burden before allogeneic transplantation and early post-transplant minimal residual disease predicts survival in patients with acute myeloid leukemia

The burden disease before allogeneic transplantation (HSCT) or the early post-transplant minimal residual disease (MRD) are both predictive parameters for relapse and post-HSCT survival in acute myeloid leukemia (AML). Nonetheless, the combination of both can provide more accurate information to identify high risk patients. To analyze the impact of pre-HSCT disease burden (MRD- vs. MRD + vs. active disease (AD), the early post-transplant MRD (posMRD + vs. posMRD-), and the combination of both pre- and post-HSCT disease status of the post-HSCT outcomes in AML patients. We retrospectively analyzed 173 patients with AML who underwent HSCT in a single institution, patients were classified according to pre-HSCT disease status, and post-HSCT MRD. MRD was measured by multiparameter flow cytometry using a cut-off of 0.1% for MRD+. The post-HSCT outcomes were analyzed based on the pre-transplant status, post-transplant status, and by combining both parameters. Patients with AD and MRD + before HSCT had worse 3y-event free (EFS) and overall survival (OS) than MRD- patients, due to a higher cumulative incidence of relapse (CIR). Also, patients with posMRD + had worse outcomes than posMRD- group. In the combined analysis, patient with MRD-/posMRD- had the best EFS and OS (3y-EFS 66.5%, 3y-OS 70.0%). Patients with MRD+/posMRD- have worse prognosis (3y-EFS 39.0%, 3y-OS 54.0%) and specially the group with AD/MRD- (3y-EFS 13.5%, 3y-OS 22.0%) and posMRD + regardless pre-HSCT disease status(3y-EFS 26.5%, 3y-OS 28.0%) had dismal OS and EFS. The combination of pre-HSCT disease burden and post-HSCT MRD measurements help us for identifying high-risk subgroups. Any level of pre-transplant disease (MRD+, and especially patients with active AD) is a risk factor, even when MRD- was achieved post-transplant. Patients with post-transplant MRD + also had an adverse prognosis. These should be target groups for implementing tailored pre- and post-transplant strategies to improve outcomes.

Evolution of Allogeneic Stem Cell Transplantation: Main Focus on AML

In recent years, treatments in the field of hematologic malignancies have undergone significant evolution; allogeneic hematopoietic stem cell transplantation (allo-HSCT) has shifted from an "ultimate" therapy to becoming a component of a comprehensive therapeutic strategy for acute myeloid leukemia (AML). Advances in risk stratification (including molecular profiling and measurable residual disease assessment), conditioning regimens, and graft-versus-host disease (GVHD) prophylaxis-such as post-transplant cyclophosphamide-have improved outcomes and expanded donor selection and transplant eligibility. We should not only focus on the transplantation procedure but also consider various therapeutic components, including chemotherapy, targeted therapy (possibly including chimeric antigen receptor T-cell therapy), and post-transplant maintenance therapy, which need to be orchestrated within the broader context of leukemia treatment. In this review, we summarized key developments in allo-HSCT for AML and aim to "decipher" each component of transplantation.

Pretransplant MRD does not seem to affect survival in NPM1-mutated AML undergoing allogeneic stem cell transplantation

ABSTRACT

Whether patients with acute myeloid leukemia (AML) harboring nucleophosmin mutations (NPM1mut) and measurable residual disease (MRD) should undergo allogeneic stem cell transplantation (allo-SCT) in complete remission (CR) remains debatable. This study assessed whether bone marrow (BM) NPM1mut MRD, detected via quantitative reverse transcription polymerase chain reaction (qRT-PCR) with 10-5 sensitivity, influences allo-SCT benefit. Data from 4 German transplantation centers included 174 patients with AML NPM1mut who underwent first allo-SCT between 2011 and 2022. Among 122 patients transplanted in CR, pre-allo-SCT MRD was positive in 54%. After allo-SCT, BM MRD negativity increased from 65% (day +30) to 73% (day +100), with FMS-like tyrosine kinase 3-internal tandem duplication and ELN risk profile affecting MRD conversion at day +30. No significant difference in leukemia-free survival (LFS) or overall survival (OS) was observed based on pretransplant MRD (3-year LFS MRD positive [MRD+], 60% vs MRD negative [MRD-], 74%; hazard ratio [HR], 1.5; P = .28; 3-year OS MRD+, 68% vs MRD-, 78%; HR, 1.42; P = .39). MRD persistence and molecular relapse outcomes did not differ (P = .8). Adverse molecular risk (HR, 4.69; P = .003) and relapsed/refractory disease (HR, 2.83/3.59; P = .005/0.001) predicted poor prognosis, while posttransplant maintenance improved survival (HR, 0.48; P = .06). Our findings suggest that in patients with NPM1mut AML MRD positivity at transplant, as assessed by qRT-PCR do not experience worse posttransplant outcomes.

Higher risk of GVHD but better long-term survival: impact of p-ALG versus r-ATG in high-risk hematological malignancy patients following MSDT

PURPOSE

Disease relapse and graft-versus-host disease (GVHD) represent significant clinical challenges for high-risk hematological malignancies (HM) patients undergoing HLA-matched sibling donor transplantation (MSDT). How to balance the effect of GVHD and Graft versus leukemia (GVL) remains unclear for high-risk HM patients receiving MSDT. Here, we conducted a retrospective study to compare the efficacy in preventing disease relapse of 2 lymphocyte-depleting antibodies (r-ATG vs p-ALG) as the GVHD prevention strategy.

METHOD

A retrospective analysis was conducted on 48 patients with high-risk HM patients who underwent MSDT at our center from January 2019 to January 2024. Among them, 22 patients were in the p-ALG group (45mg/kg), and 26 patients were in the r-ATG group (3.5-4.5mg/kg). The primary end point of this study was disease relapse.

RESULTS

We found that the p-ALG group had a higher 3-year cumulative incidence of chronic GVHD than the r-ATG group (64.4% ± 13.6% vs. 28.8% ± 9.7%, P = 0.016). There was no significant difference in total acute GVHD (aGVHD) (54.5% ± 11% vs.26.9% ± 8.9%, P = 0.81) and 3-year extensive cGVHD (20.3% ± 11.3% vs. 7.9% ± 5.5%, P = 0.27) between the 2 groups. In terms of patient prognosis, the p-ALG group showed a higher 3-year overall survival rate compared to the r-ATG group (100% vs. 75.5% ± 8.8%, P = 0.039). The 3-year disease-free survival (DFS) rate was significantly higher in the p-ALG group compared to the r-ATG group (95.5% ± 4.4% versus 61% ± 10.6%, P = 0.046). Furthermore, the p-ALG group exhibited a longer duration of disease remission after transplantation, as evidenced by a lower 3-year cumulative incidence of post-transplantation Minimal Residual Disease positivity (post-MRD+) compared to the r-ATG group (4.5% ± 4.4% versus 40.5% ± 11%, P = 0.022).

CONCLUSION

In comparison to r-ATG, the administration of low-dose p-ALG (45mg/kg) in high-risk HM patients receiving MSDT is associated with an increased incidence of GVHD but results in a more favorable survival prognosis.

Measurable Residual Disease Analysis by Flow Cytometry: Assay Validation and Characterization of 385 Consecutive Cases of Acute Myeloid Leukemia

Background/Objectives: Acute myeloid leukemia (AML) is a biologically heterogeneous malignancy with a variable prognosis. Despite many patients achieving complete remission, relapse remains common, underscoring the need for effective prognostic markers. Measurable residual disease (MRD) has emerged as a critical prognostic indicator, associated with higher relapse risk and shorter survival. This study reports on our initial experience of MRD detection by flow cytometry in 385 bone marrow samples from 126 AML patients. Methods: The flow cytometry MRD assay, validated according to stringent consensus recommendations, consists of a 3-tube, 10-color panel incorporating a broad spectrum of lineage differentiation markers. Analytical specificity, sensitivity, precision, and reproducibility were evaluated, demonstrating the assay's robustness. Results: The results reveal distinct immunophenotypic aberrancies in all AML cases, with consistent identification of aberrant immunophenotypes in follow-up specimens. AML MRD was detected in 32 out of 126 patients (25%) and in 77 out of 385 analyses (20%), with a median aberrant blast percentage of 1.87% (range, 0.01-12). A change in immunophenotype was documented in 21% of the MRD-positive cases. MRD positivity detected in the first sample studied was associated with reduced overall survival (HR: 5.153; p < 0.0001). Conclusions: Our findings support the integration of flow cytometric MRD analysis into routine clinical practice to enhance risk stratification and treatment planning for AML patients, as currently recommended by professional guidelines.

Prospective, Randomized, Comparative Study of Myeloablative Fludarabine/Busulfan and Fludarabine/Busulfan/Total Body Irradiation Conditioning in Myeloid Diseases

Background/Objectives: Allogeneic hematopoietic stem cell transplantation (alloSCT) is a curative treatment for myeloid diseases, yet relapse remains the major cause of post-transplant mortality. To reduce the risk of recurrence, we evaluated the addition of 400 cGy total body irradiation (TBI) to conditioning with fludarabine-busulfan (Flu/Bu4). Methods: In this prospective study, 46 patients with myeloid diseases were randomized to Flu/Bu4 or Flu/Bu4/TBI conditioning group. The Flu/Bu4 conditioning regimen consisted of fludarabine 40 mg/m2 on days -6 to -3 followed by busulfan 130 mg/m2 on days -6 to -3. Flu/Bu4/TBI conditioning regimen added 400 cGy TBI on day -1 to the FluBu4 regimen. Results: Among 34 acute myeloid leukemia (AML) patients, relapse was numerically lower in those who received Flu/Bu4/TBI (25%) versus Flu/Bu4 (44.4%) at three years (HR = 0.58, 95% CI 0.19 to 1.81, p = 0.35). Flu/Bu4/TBI appeared to increase the risk of non-relapse mortality (NRM) vs. Flu/Bu4 in AML patients at three years (25.0% versus 11.1%; HR = 2.11, 95% CI 0.51 to 8.83, p = 0.65). Overall survival (OS) was similar in AML patients undergoing conditioning with Flu/Bu4 (72.2%) versus Flu/Bu4/TBI (62.5%) at one year (p = 0.4). Conclusions: In conclusion, the addition of 400 cGy TBI to Flu/Bu4 reduced the risk of relapse but did not improve OS as a consequence of higher regimen-related mortality. Clinicaltrials.gov identifier: NCT01366612.

Is There (Still) a Place for Sequential Conditioning?

There is still an unmet need for the treatment of high-risk hematological malignancies. To date, allogeneic stem cell transplantation remains the only chance of cure. Most patients suffering from high-risk hematological malignancies are of an older age and often present with comorbidities. Moreover, patients achieving remission often suffer from early relapse. Amongst the different treatment options, sequential conditioning has yet to prove its value against other conditioning regimens. Sequential conditioning relies on a short course of intensive chemotherapy that is quickly followed by immunosuppressive conditioning before allogeneic stem cell transplantation. Here, we will try to determine which patients can benefit from sequential conditioning. Amongst the different sequential regimens, we will also try to assess if one regimen is better than all the others. Despite the several studies conducted on sequential conditioning, very few are prospective work and head-to-head comparisons are almost inexistant. Sequential conditioning also relies on the use of prophylactic donor lymphocyte infusion post-transplantation. Hence, limiting non-relapse complications is of primary importance to the allow administration of post-transplant treatment. In the era of new targeting therapies, is there still a place for sequential conditioning? Can patients benefit from an association of new therapeutic agents and sequential conditioning?

Measurable residual disease monitoring in AML: Prospects for therapeutic decision-making and new drug development

Measurable residual disease (MRD) is strongly associated with risk of relapse and long-term survival outcomes in patients with acute myeloid leukemia (AML). Apart from its clear prognostic impact, MRD information is also increasingly used to guide therapeutic decision-making, including selection of appropriate patients for stem cell transplant, use of post-transplant maintenance, and candidacy for non-transplant maintenance therapies or MRD-directed clinical trials. While much progress has been made in accurately assessing MRD and understanding its clinical importance, many questions remain about how to optimize MRD testing and guide treatment decisions for individual patients. In this review, we discuss the common methods to assess MRD in AML and the prognostic impact of MRD across common clinical scenarios. We also review emerging and investigational strategies to target MRD and discuss some of the important unanswered questions and challenges in the field.

Impact of high-sensitivity flow cytometry on peri-transplant minimal residual disease kinetics in acute leukemia

Minimal residual disease (MRD) detected before hematopoietic cell transplantation (HCT) is associated with adverse outcomes in patients with high-risk acute leukemia. However, the ideal time points for post-transplant MRD assessment and the clinical significance of low levels of residual disease in this context are unclear. We conducted a prospective real-world analysis of high-sensitivity flow cytometry MRD performed before and after transplant (at days 30, 60 and 100) in 77 acute leukemia patients. The aim was to evaluate the kinetics of disease elimination and correlate it with transplant outcomes. Pre-transplant MRD was negative in 42 (MRD-) and positive in 35 patients (MRD+). Post-transplant MRD assessment was feasible at day 30 (n = 30, 38.9%), day 60 (n = 27, 35.0%) and day 100 (n = 60, 77.9%). Relapses occurred in 8 patients in the MRD + group (22.9%) and three in the MRD-negative group (7.1%), p = 0.02. Pre-transplant MRD correlated with a decrease in overall survival (OS; 87.9% MRD- vs. 54.0% MRD+) and event-free survival (EFS; 85.3% MRD- vs. 51.1% MRD+), p = 0.001. Cumulative incidence of relapse (CIR) was 17.5% in MRD + vs. 2.6% in MRD- (p = 0.049). Non-relapse mortality (NRM) was 31.4% in MRD + vs. 12.1% in MRD- (p = 0.019). One-year OS was higher in patients with negative MRD at d100 (92.4%, 95% CI: 0.81-0.971) than positive d100 MRD (53.3%, 95% CI: 0.177-0.796), p < 0.0001. Disease status and d100 MRD were associated with OS, EFS and CIR. Differences in NRM between leukemia types (ALL: 18.9% MRD- vs. 50% MRD+, and AML 0% MRD- vs. 21.7% MRD+, p = 0.0158) were also observed. In conclusion, pre-transplant MRD assessed by highly sensitive flow cytometry accurately identified patients with adverse prognoses. Persistent MRD after HCT could predict relapse with high specificity and clinical sensitivity. These results highlight the importance of incorporating peri-transplant MRD kinetics into the routine treatment of acute leukemia, particularly in low/middle-income countries.

Long-term real-world evidence of CPX-351 of high-risk patients with AML identified high rate of negative MRD and prolonged OS

ABSTRACT

CPX-351 has been approved for patients with therapy-related acute myeloid leukemia (t-AML) or AML with myelodysplasia-related changes (MRC-AML). No extensive data are available on measurable residual disease (MRD) and long-term clinical outcome using CPX-351 in AML in real life. We retrospectively collected data from 168 patients in 36 centers in France and Italy who had received 1 or 2 cycles of induction with CPX-351. All patients were aged >18 years and had newly diagnosed, untreated t-AML or MRC-AML. With a median follow-up of 3 years, the median overall survival (OS) was 13.3 months. The median OS was 20.4 months vs 12.9 months for patients with MRD below or above 10-3, respectively (P = .006). In a multivariate analysis, only MRD >10-3 was associated with a poorer OS (hazard ratio, 2.6; 95% confidence interval, 1.2-5.5; P = .013). We also observed a trend toward a better median OS in patients who underwent hematopoietic stem cell transplantation with MRD <10-3 (not reached vs 26.0 months; P = .06). Achievement of MRD negativity contributed to the improvement of OS in the overall population and, maybe, in patients receiving transplant. These data provide the rationale for the 2 ongoing studies evaluating CPX-351 vs 7+3 in non-MRC-AML and non-t-AML using MRD as the primary end point for ALFA-2101 phase 2 clinical trial and event-free survival for AMLSG 30-18 phase 3 clinical trial.

Significance of Measurable Residual Disease in Patients Undergoing Allogeneic Hematopoietic Cell Transplantation for Acute Myeloid Leukemia

Allogeneic hematopoietic cell transplantation (HCT) remains an important curative-intent treatment for many patients with acute myeloid leukemia (AML), but AML recurrence after allografting is common. Many factors associated with relapse after allogeneic HCT have been identified over the years. Central among these is measurable ("minimal") residual disease (MRD) as detected by multiparameter flow cytometry, quantitative polymerase chain reaction, and/or next-generation sequencing. Demonstration of a strong, independent prognostic role of pre- and early post-HCT MRD has raised hopes MRD could also serve as a predictive biomarker to inform treatment decision-making, with emerging data indicating the potential value to guide candidacy assessment for allografting as a post-remission treatment strategy, the selection of conditioning intensity, use of small molecule inhibitors as post-HCT maintenance therapy, and preemptive infusion of donor lymphocytes. Monitoring for leukemia recurrence after HCT and surrogacy for treatment response are other considerations for the clinical use of MRD data. In this review, we will outline the current landscape of MRD as a biomarker for patients with AML undergoing HCT and discuss areas of uncertainty and ongoing research.

cfDNA Chimerism and Somatic Mutation Testing in Early Prediction of Relapse After Allogeneic Stem Cell Transplantation for Myeloid Malignancies

Background: Disease relapse is a primary cause of treatment failure after hematopoietic stem cell transplantation in the treatment of malignancy. Consolidation therapy early after transplantation may reduce this risk, but it is difficult to administer in the setting of various post-transplant complications. We proposed that testing donor cell chimerism and for persistent minimal residual disease (MRD) with next-generation sequencing (NGS) of plasma cell-free DNA (cfDNA) early after transplantation would identify those patients at higher risk of relapse who would possibly benefit from consolidation therapy. Methods: We enrolled 20 subjects with known tumor-associated somatic mutations into this prospective pilot study, testing plasma samples before and at 28, 56, and 84 days after transplantation. Pre- and post-transplant bone marrow samples were also analyzed. All samples were subjected to an agnostic, commercially available panel covering 302 genes. Results: Significantly more mutations (p < 0.0001) were detected in the plasma cfDNA than in the bone marrow cells in pre-transplant testing (92 versus 61 mutations, respectively), most likely reflecting sampling variation when bone marrow was used. Two subjects were negative for MRD in staging studies immediately before transplants. Most (19/20) subjects had intermittent or sustained MRD detected in post-transplant plasma cfDNA testing, albeit with much lower average variant allele frequencies (VAFs). Six out of 20 subjects suffered relapses within 12 months after transplantation, and all 6 could be identified by adverse-risk driver mutations that persisted after transplantation. No patients who cleared the adverse-risk mutations relapsed. Donor chimerism using cfDNA fell for all relapsed patients and contributed to the identification of patients at early risk for relapse. Conclusions: These data demonstrate that testing plasma cfDNA for persistent leukemia-associated somatic mutations and donor chimerism as early as 28 days after transplantation will identify a subset of patients with high-risk mutations who are at high risk of relapse. This early assessment of relapse risk may facilitate modifications to the treatment plan, reducing the risk of treatment failure.

Measurable residual disease as predictor of post-day +100 relapses after allografting in adult AML

ABSTRACT

Measurable residual disease (MRD) by multiparametric flow cytometry (MFC) before allogeneic hematopoietic cell transplantation (HCT) identifies patients at high risk of acute myeloid leukemia (AML) relapse, often occurring early after allografting. To examine the role of MFC MRD testing to predict later relapses, we examined 935 adults with AML or myelodysplastic neoplasm/AML transplanted in first or second morphologic remission who underwent bone marrow restaging studies between day 70 and 100 after HCT and were alive and without relapse by day +100. Of 935 adults, 136 (15%) had MRD before HCT, whereas only 11 (1%) had MRD at day +70 to +100. In day +100 landmark analyses, pre-HCT and day +70 to +100 MFC MRD were both associated with relapse (both P < .001), relapse-free survival (RFS; both P < .001) overall survival (OS; both P < .001), and, for post-HCT MRD, nonrelapse mortality (P = .001) after multivariable adjustment. Importantly, although 126/136 patients (92%) with MRD before HCT tested negative for MRD at day +70 to +100, their outcomes were inferior to those without MRD before HCT and at day +70 to +100, with 3-year relapse risk of 40% vs 15% (P < .001), 3-year RFS of 50% vs 72% (P < .001), and 3-year OS of 56% vs 76% (P < .001), whereas 3-year nonrelapse mortality estimates were similar (P = .53). Thus, despite high MRD conversion rates, outcomes MRD positive/MRD negative (MRDneg) patients are inferior to those of MRDneg/MRDneg patients, suggesting all patients with pre-HCT MRD should be considered for preemptive therapies after allografting.

Measurable residual mutated IDH2 before allogeneic transplant for acute myeloid leukemia

Routine genetic profiling of acute myeloid leukemia (AML) at initial diagnosis has allowed subgroup specific prognostication, drug development, and clinical management strategies. The optimal approach for treatment response assessment for AML subgroups has not yet however been determined. A nationwide cohort of 257 adult patients in first remission (CR1) from AML associated with an IDH2 mutation (IDH2m) undergoing allogeneic transplant during the period 2013-2019 in the United States had rates of relapse and survival three years after transplantation of 24% and 71%, respectively. Pre-transplant clinical flow cytometry assessment was not useful in stratifying patients based on risk of post-transplant relapse or death. DNA-sequencing was performed on CR1 blood collected within 100 days before transplant. Persistent detection of IDH2m was common (51%) and associated with increased relapse and death compared to testing negative. Co-mutation at initial diagnosis with mutated NPM1 and/or FLT3-ITD was common in this cohort (41%) and use of these validated MRD markers provided superior stratification compared to IDH2m testing. Patients testing negative for IDH2m prior to transplant had low relapse-related death, regardless of conditioning intensity. Post-transplant relapse rates for those with persistently detectable IDH2m in pre-transplant remission were lower after the FDA approval of enasidenib in August 2017.

Relationship between donor source, pre-transplant measurable residual disease, and outcome after allografting for adults with acute myeloid leukemia

Lack of HLA-matched related/unrelated donor remains a barrier to allogeneic hematopoietic cell transplantation (HCT) for adult acute myeloid leukemia (AML), with ongoing uncertainty about optimal donor type if more than one alternative donor is available. To assess the relationship between donor type, pre-HCT measurable residual disease (MRD), and post-HCT outcomes, we retrospectively analyzed 1265 myelodysplastic neoplasm (MDS)/AML and AML patients allografted in first or second remission with an HLA-matched sibling (MSD) or unrelated donor (MUD), HLA-mismatched unrelated donor (MMD), an HLA-haploidentical donor, or umbilical cord blood (UCB) at a single institution. Relapse risk was non-significantly higher after HLA-haploidentical and lower after UCB HCT. Non-relapse mortality (NRM) was significantly higher in patients undergoing MMD HCT, HLA-haploidentical HCT, and UCB, translating into significantly lower relapse-free survival (RFS) and overall survival for MMD and HLA-haploidentical HCT. There was a significant interaction between conditioning intensity and post-HCT outcomes for UCB HCT with better RFS for UCB HCT after MAC but higher NRM after non-MAC. In patients with pre-HCT MRD receiving MAC, relapse risk was significantly lower and RFS higher in those who underwent UCB HCT in comparison to MSD/MUD. Together, UCB HCT is a valuable alternative for MAC HCT, particularly in patients with pre-HCT MRD.

Measurable residual mutated IDH1 before allogeneic transplant for acute myeloid leukemia

Measurable residual disease (MRD) in adults with acute myeloid leukemia (AML) in complete remission is an important prognostic marker, but detection methodology requires optimization. Persistence of mutated NPM1 or FLT3-ITD in the blood of adult patients with AML in first complete remission (CR1) prior to allogeneic hematopoietic cell transplant (alloHCT) associates with increased relapse and death after transplant. The prognostic implications of persistence of other common AML-associated mutations, such as IDH1, at this treatment landmark however remain incompletely defined. We performed testing for residual IDH1 variants (IDH1m) in pre-transplant CR1 blood of 148 adult patients undergoing alloHCT for IDH1-mutated AML at a CIBMTR reporting site between 2013 and 2019. No statistically significant post-transplant differences were observed between those testing IDH1m positive (n = 53, 36%) and negative pre-transplant (overall survival (OS): p = 0.4; relapse: p = 0.5). For patients with IDH1 mutated AML co-mutated with NPM1 and/or FLT3-ITD, only detection of persistent mutated NPM1 and/or FLT3-ITD was associated with significantly higher rates of relapse (p = 0.01). These data, from the largest study to date, do not support the detection of IDH1 mutation in CR1 blood prior to alloHCT as evidence of AML MRD for increased post-transplant relapse risk.

Fludarabine melphalan reduced intensity conditioning vs radiation-based myeloablative conditioning in patients undergoing allogeneic transplantation for acute myeloid leukemia with measurable residual disease

Patients with AML and measurable residual disease (MRD) undergoing allogeneic hematopoietic cell transplantation (HCT) may benefit from myeloablative conditioning (MAC) when feasible to reduce relapse risk. Fludarabine-Melphalan (FluMel) is a common reduced intensity conditioning (RIC) regimen; however, data in MRD+ patients is sparse. We performed a retrospective review of AML patients who underwent their first HCT (2016-2021) without morphologic disease at City of Hope who had pre-transplant marrow evaluated for MRD using multicolor flow cytometry (MFC) and received radiation-based MAC or FluMel conditioning. We identified 312 patients; 44 with MRD+ disease pre-HCT. The 24-month overall survival (OS), leukemia-free survival (LFS) and cumulative incidence of relapse (CIR) were 47.7%, 40.9%, and 38.6% in MRD+, and 78.0%, 73.9%, and 14.6% in MRD- patients. Radiation-based MAC was given to 136 (43.5%) patients (n = 20 with MRD+) and FluMel was given to 174 (55.8%) patients (n = 24 with MRD+). In patients with MRD+, there was no statistically significant difference between those who received MAC vs. FluMel in 24-month OS (60% vs. 38%, p = 0.21), or CIR (35% vs. 42%, p = 0.59), respectively. Our data substantiates the adverse impact of MRD in patients with AML undergoing HCT; FluMel is a reasonable option for MRD+ patients unfit for MAC.

Increased Co-Expression of PD-L1 and CTLA-4 Predicts Poor Overall Survival in Patients with Acute Myeloid Leukemia Following Allogeneic Hematopoietic Stem Cell Transplantation

Purpose

Our previous study has demonstrated that high expression of immune checkpoints (ICs) was significantly associated with adverse clinical outcomes in patients with acute myeloid leukemia (AML). This study aims to investigate the significance of the alteration of IC co-expression for evaluating the prognosis of AML patients following allogeneic hematopoietic stem cell transplantation (allo-HSCT).

Patients and Methods

Quantitative real-time PCR (qRT-PCR) data of bone marrow (BM) samples from 62 de novo AML patients, including 37 patients who received allo-HSCT and 25 patients who received chemotherapy only, were used for prognostic analysis.

Results

High expression of PD-1, PD-L1, PD-L2, CTLA-4, and LAG-3 was associated with poor overall survival (OS) in AML patients receiving allo-HSCT, while the expression levels of PD-1, PD-L2, CTLA-4, and LAG-3, other than PD-L1, were not significantly correlated with OS in AML patients receiving chemotherapy. Importantly, PD-L1/CTLA-4 was the best combination model for predicting poor OS in AML patients following allo-HSCT, especially combined with minimal residual disease (MRD).

Conclusion

High expression of ICs in BM of AML patients following allo-HSCT was related to poor outcomes, and increasing co-expression of PD-L1 and CTLA-4 might be one of the best immune biomarkers to predict outcomes in patients with AML.

Pre-emptive therapeutic decisions based on measurable residual disease status in acute myeloid leukemia: ready for prime time?

The use of measurable residual disease (MRD) as a biomarker for prognostication, risk stratification, and therapeutic decision-making in acute myeloid leukemia (AML) is gaining prominence. MRD monitoring for NPM1-mutated and core-binding factor AML using PCR techniques is well-established for assessing disease after intensive chemotherapy. AML with persistent FLT3-ITD MRD post-intensive chemotherapy and pre-allogeneic hematopoietic cell transplantation (pre-allo-HCT) is associated with an increased risk of relapse and lower survival. Pre-allo-HCT MRD is an independent risk factor for post-allo-HCT outcomes, including relapse and death. Therefore, preemptive interventions on the natural history of MRD positivity are an active area of research beyond its initial prognostic function. Targeting MRD in AML with innovative treatment strategies can improve patient outcomes.

[Place of hematopoietic stem cell transplantation for very high risk acute myeloblastic leukemia and myelodysplastic syndromes (SFGM-TC)]

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a potentially curative treatment for acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS). However, these transplants are complicated by a high rate of relapse in very high cytogenetic risk or refractory diseases. The benefit of this therapeutic strategy for these serious malignant hemopathies could therefore be reassessed. As part of the 14th workshop for the harmonization of allograft practices organized by the francophone society of bone marrow transplantation and cellular therapy (SFGM-TC) (SFGM-TC) in Lille in September 2023, the role of allograft for very high risk or refractory AML and MDS was challenged after analysis of published studies.

Measurable residual disease assessment prior to allogeneic hematopoietic stem cell transplantation in acute myeloid leukemia and myelodysplastic syndromes: a 20-year monocentric study

Patients with acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS) who undergo allogeneic hematopoietic stem-cell transplantation (alloHSCT) can have divergent survival outcomes while all in morphological complete remission (CR). Techniques of measurable residual disease (MRD) have allowed us to refine their prognosis in two categories: MRD-positive and MRD-negative patients. We conducted a monocentric retrospective study (01/2000-12/2020) to assess the prognosis of pretransplant MRD status measured by multiparametric flow cytometry (MFC) and molecular biology assessed by PCR. 192 patients were included. The median follow-up period was 77 months. Among patients undergoing alloHSCT in CR, overall survival (median-OS: 130.6 vs. 16.0 months, P < 0.001), disease-free survival (median-DFS: 109.6 vs. 7.1 months, P < 0.001) and cumulative incidence of relapse (12-month CIR: 7.3% vs. 33.7%, P < 0.0001) were significantly different between MRD-negative and MRD-positive patients. Patients with discordant intermethod results had intermediate DFS. MRD-negative patients according to molecular PCR-based techniques, WT1 overexpression and MFC had longer median-DFS, compared to MRD-positive patients (P = 0.001, P < 0.001, P < 0.001, respectively). Looking into subgroups, MRD-positive patients among the ELN2017 adverse-category (P < 0.0001), myeloablative and reduced-intensity conditioning regimens (P < 0.0001, P = 0.005), < 60-year patients (P < 0.001) and AML patients (P < 0.001) were associated with lower DFS. This difference was not found in ≥ 60-year patients (P = 0.27) and MDS patients (P = 0.70). MRD-positive patients within the favorable/intermediate ELN2017 category trended toward lower DFS (P = 0.05). We confirmed that MRD status prior to alloHSCT is a strong prognostic factor for OS, DFS and CIR. Combining MFC and molecular-PCR techniques to assess MRD seems primordial as inter-method discordance can be consequential.

Exploration of ETV6::ABL1-positive AML with concurrent NPM1 and FLT3-ITD mutations

ETV6::ABL1 is a rare fusion gene that found in MPN, ALL, and AML. It has a complex and diverse formation mechanism due to the reciprocal orientations of the ETV6 and ABL1 genes relative to the centromeres. NPM1 is frequently mutated in adult AML, often accompanied by FLT3-ITD, which suggests molecular synergisms in AML pathogenesis. Previous reports on ETV6::ABL1 mostly focus on FLT3-ITD. In this study, we present a case of AML with ETV6::ABL1, along with NPM1 and FLT3-ITD. The patient showed a rapid increase in primitive cells at the initial stage, along with the presence of immature granulocytes and erythrocytes. Through cytogenetic analysis, fluorescence in situ hybridization (FISH), and RNA-seq, we elucidated the mechanism behind the formation of the ETV6::ABL1 fusion gene. Despite conventional chemotherapy failure and rapid tumor proliferation, we attempted to add FLT3 inhibitor sorafenib to the treatment, along with chemotherapy bridging to haploidentical transplantation. After haplo-HSCT, a combination of sorafenib and dasatinib was administered as maintenance therapy. The patient achieved complete remission (CR) and maintained it for 11 months. The intricate genetic landscape observed in this case presents diagnostic dilemmas and therapeutic challenges, emphasizing the importance of a comprehensive understanding of its implications for disease classification, risk stratification, and treatment selection.

Lower intensity therapy with cladribine/low dose cytarabine/venetoclax in older patients with acute myeloid leukemia compares favorably with intensive chemotherapy among patients undergoing allogeneic stem cell transplantation

BACKGROUND

Allogeneic stem cell transplantation (SCT) remains the best consolidative modality in most patients with acute myeloid leukemia (AML). Along with factors directly pertaining to SCT, pretransplantation disease control, performance status, and prior treatment-related complications are important factors that affect posttransplantation survival outcomes.

METHODS

The authors compared the survival outcomes of patients ≥60 years of age treated on the phase 2 clinical trial of venetoclax (Ven) added to cladribine (CLAD) and low dose cytarabine (LDAC) alternating with azacitidine (CLAD/LDAC/Ven arm) (NCT03586609) who underwent allogeneic SCT in first remission to a retrospective cohort of patients ≥60 years of age who underwent SCT after intensive chemotherapy. Intensive chemotherapy was defined as the use of cytarabine >1 g/m2 and anthracyclines during induction/consolidation.

RESULTS

Thirty-five patients at median age of 68 years in the CLAD/LDAC/Ven arm were compared to 42 patients at a median age of 62 years in the intensive therapy arm. The 2-year relapse-free survival was superior with CLAD/LDAC/Ven versus intensive chemotherapy (88% vs. 65%; p = .03) whereas the 2-year overall survival (OS) was comparable (84% vs. 70%; p = .14). On a competing event analysis, the 2-year cumulative incidence of relapse (CIR) was significantly lower with CLAD/LDAC/Ven versus intensive chemotherapy (2.9% vs. 17.2%, Gray's p = .049) whereas nonrelapse mortality was comparable (16.2% vs. 17.1%; p = .486).

CONCLUSION

In conclusion, treatment with CLAD/LDAC/Ven was associated with favorable outcomes in older patients who underwent subsequent allogeneic SCT. The OS was comparable to that with intensive chemotherapy followed by allogeneic SCT, but the CIR rate was significantly lower.

WT1 Expression Is Associated with Poor Overall Survival after Azacytidine and DLI in a Cohort of Adult AML and MDS Patients

Introduction: Post-transplant relapse of acute myeloid leukemia and myelodysplastic syndrome faces restricted effective salvage regimens. We retrospectively analyzed the use of Azacitidine-donor lymphocyte infusion (AZA/DLI) in this setting. Furthermore, data on bone marrow Wilms tumor gene 1 (WT1) expression were collected. Methods: A Cox proportional hazards model, an outcome-oriented approach for the lowest smoothed plot of the martingale residuals, was performed for the cut-point determination of the respective WT1 expression levels. Finally, a Cox proportional hazards model investigated the association of overall survival (OS) with predictors. Results: An overall response of 41.4% with a median duration of 11.9 months for stable disease and 19.5 months for complete response (CR) patients was achieved. The disease risk index (DRI) high-/very high-risk patients had a shorter OS of 4.4 months than intermediate-risk patients, with 14.5 months, p = 0.007. At transplant, WT1-overexpressing patients (>150 copies) had a shorter median OS of 5.3 months than low-WT1-expressing ones, with 13.5 months, p = 0.024. Furthermore, patients with ≤1000 WT1 copies at relapse had a significantly longer OS with 15.3 months than patients overexpressing WT1, with 4.4 months, p = 0.0002. Conclusions: DRI and WT1 expression associate significantly with OS after AZA/DLI. Hence, WT1 may represent an MRD marker, especially in CR patients at high risk.

Molecular relapse after first-line intensive therapy in patients with CBF or NPM1-mutated acute myeloid leukemia - a FILO study

Patients with Core-Binding Factor (CBF) and NPM1-mutated acute myeloid leukemia (AML) can be monitored by quantitative PCR after having achieved first complete remission (CR) to detect morphologic relapse and drive preemptive therapy. How to best manage these patients is unknown. We retrospectively analyzed 303 patients with CBF and NPM1-mutated AML, aged 18-60 years, without allogeneic hematopoietic cell transplantation (HCT) in first CR, with molecular monitoring after first-line intensive therapy. Among these patients, 153 (51%) never relapsed, 95 (31%) had molecular relapse (53 received preemptive therapy and 42 progressed to morphologic relapse at salvage therapy), and 55 (18%) had upfront morphologic relapse. Patients who received preemptive therapy had higher OS than those who received salvage therapy after having progressed from molecular to morphologic relapse and those with upfront morphologic relapse (three-year OS: 78% vs. 51% vs. 51%, respectively, P = 0.01). Preemptive therapy included upfront allogeneic HCT (n = 19), intensive chemotherapy (n = 21), and non-intensive therapy (n = 13; three-year OS: 92% vs. 79% vs. 58%, respectively, P = 0.09). Although not definitive due to the non-randomized allocation of patients to different treatment strategies at relapse, our study suggests that molecular monitoring should be considered during follow-up to start preemptive therapy before overt morphologic relapse.

Persistent or New Cytopenias Predict Relapse Better than Routine Bone Marrow Aspirate Evaluations After Hematopoietic Cell Transplantation for Acute Leukemia or Myelodysplastic Syndrome in Children and Young Adult Patients

The clinical value of serial routine bone marrow aspirates (rBMAs) in the first year after allogeneic hematopoietic cell transplantation (alloHCT) to detect or predict relapse of acute leukemia (AL) and myelodysplastic syndrome (MDS) in pediatric and young adult patients is unclear. The purpose of this analysis was to determine if assessment of minimal residual disease (MRD) by multiparameter flow cytometry (MFC, MFC-MRD) or donor chimerism (DC) in rBMAs or serial complete blood counts (CBCs) done in the year after alloHCT predicted relapse of AL or MDS in pediatric and young adult patients. We completed a retrospective analysis of patients with AL or MDS who had rBMAs performed after alloHCT between January 2012 and June 2018. Bone marrow (BM) was evaluated at approximately 3, 6, and 12 months for disease recurrence by morphology, MFC-MRD, and percent DC by short tandem repeat molecular testing. CBCs were performed at every clinic visit. The main outcome of interest was an assessment of whether MFC-MRD or DC in rBMAs or serial CBCs done in the year after alloHCT predicted relapse in AL or MDS pediatric and young adult patients. A total of 121 recipients with a median age of 13 years (range 1 to 32) were included: 108 with AL and, 13 with MDS. A total of 423 rBMAs (median 3; 0 to 13) were performed. Relapse at 2 years was 23% (95% CI: 16% to 31%) and at 5 years 25% (95% CI: 18% to 33%). One hundred fifty-four of 157 (98%) rBMAs evaluated for MRD by MFC were negative and did not preclude subsequent relapse. Additionally, low DC (<95%) did not predict relapse and high DC (≥95%) did not preclude relapse. For patients alive without relapse at 1 year, BM DC (P = .74) and peripheral T-cell DC (P = .93) did not predict relapse. Six patients with low-level T-cell and/or BM DC had a total of 8 to 20 BM evaluations, none of these patients relapsed. However, CBC results were informative for relapse; 28 of 31 (90%) relapse patients presented with an abnormal CBC with peripheral blood (PB) blasts (16 patients), cytopenias (9 patients), or extramedullary disease (EMD, 3 patients). Two patients with BM blasts >5% on rBMA had circulating blasts within 5 weeks of rBMA. Neutropenia (ANC <1.5 K/mcl) at 1 year was predictive of relapse (P = .01). Neutropenia and thrombocytopenia (<160 K/mcl) were predictive of disease-free survival (DFS) with inferior DFS for ANC <1.5 K/mcl, P = .001, or platelet count <160 K/mcl (P = .04). These results demonstrate rBMAs after alloHCT assessed for MRD by MFC and/or for level of DC are poor predictors for relapse in pediatric and young adult patients with AL or MDS. Relapse in these patients presents with PB blasts, cytopenias, or EMD. ANC and platelet count at 1-year were highly predictive for DFS.

Evaluation of European LeukemiaNet 2022 risk classification in patients undergoing allogeneic haematopoietic stem cell transplantation for acute myeloid leukaemia: Identification of a very poor prognosis genetic group

European LeukemiaNet refined their risk classification of acute myeloid leukaemia (AML) in 2022 (ELN 2022) according to the two new myeloid classifications published the same year. We have retrospectively assessed the prognostic value of the ELN 2022 in 120 AML patients undergoing allogeneic haematopoietic cell transplantation (allo-HCT), including 99 in first complete response (CR1) from 2011 to 2021 in our centre. Adverse risk patients (Adv) presented inferior outcome in terms of overall survival (OS) and leukaemia-free survival (LFS) (OS [p = 0.003], LFS [p = 0.02]), confirmed in multivariate analysis (hazard ratio [HR] for OS = 2.00, p = 0.037). These results were also seen in patients allografted in CR1. Further analysis identified a subgroup named adverse-plus (AdvP), including complex karyotype, MECOM(EVI1) rearrangements and TP53 mutations, with worse outcomes than the rest of groups of patients, including the Adv (HR for OS: 3.14, p < 0.001, HR for LFS: 3.36, p < 0.001), with higher 2-year cumulative incidence of relapse (p < 0.001). Notably, within this analysis, the outcome of Adv and intermediate patients were similar. These findings highlight the prognostic value of ELN 2022 in patients undergoing allo-HCT, which can be improved by the recognition of a poor genetic subset (AdvP) within the Adv risk group.

Targeting Molecular Measurable Residual Disease and Low-Blast Relapse in AML With Venetoclax and Low-Dose Cytarabine: A Prospective Phase II Study (VALDAC)

PURPOSE

A prospective phase II study examined the safety and efficacy of venetoclax combined with low-dose cytarabine (LDAC) in AML at first measurable residual disease (MRD) or oligoblastic relapse.

METHODS

Patients with either MRD (≥1 log10 rise) or oligoblastic relapse (blasts 5%-15%) received venetoclax 600 mg once daily D1-28 plus LDAC once daily D1-10 in 28-day cycles. The primary objective was MRD response in the MRD relapse cohort or complete remission (CR/CRh/CRi) in the oligoblastic relapse cohort.

RESULTS

Forty-eight adults with either MRD (n = 26) or oligoblastic (n = 22) relapse were enrolled. Median age was 67 years (range, 18-80) and 94% had received previous intensive chemotherapy. Patients received a median of four cycles of therapy; 17% completed ≥12 cycles. Patients with oligoblastic relapse had more grade ≥3 anemia (32% v 4%; P = .02) and infections (36% v 8%; P = .03), whereas grade 4 neutropenia (32 v 23%) or thrombocytopenia (27 v 15%) were comparable with the MRD relapse cohort. Markers of molecular MRD relapse included mutant NPM1 (77%), CBFB::MYH11 (4%), RUNX1::RUNX1T1 (4%), or KMT2A::MLLT3 (4%). Three patients with a log10 rise in IDH1/2 (12%) were included. By cycle 2 in the MRD relapse cohort, a log10 reduction in MRD was observed in 69%; 46% achieved MRD negative remission. In the oligoblastic relapse cohort, 73% achieved CR/CRh/CRi. Overall, 21 (44%) underwent hematopoietic cell transplantation. Median overall survival (OS) was not reached in either cohort. Estimated 2-year OS rate was 67% (95% CI, 50 to 89) in the MRD and 53% (95% CI, 34 to 84) in the oligoblastic relapse cohorts.

CONCLUSION

For AML in first remission and either MRD or oligoblastic relapse, venetoclax plus LDAC is well tolerated and highly effective.

Minimal residual disease monitoring in acute myeloid leukemia: Focus on MFC-MRD and treatment guidance for elderly patients

Acute myeloid leukemia (AML) is distinguished by clonal growth of myeloid precursor cells, which impairs normal hematopoiesis. Minimal residual disease (MRD) refers to the residual leukemia cells that persist after chemotherapy. Patients who test positive for MRD have a higher likelihood of experiencing a recurrence, regardless of the specific chemotherapy approach used. Multi-parameter flow cytometry (MFC), polymerase chain reaction (PCR), and next-generation sequencing (NGS) are commonly employed techniques for identifying MRD. In the context of AML, patients are frequently monitored for measurable residual disease via multi-parameter flow cytometry (MFC-MRD). In order to explore recent advancements in AML and MRD diagnosis, an extensive search of the PubMed database was conducted, focusing on relevant research in the past 20 years. This review aims to examine various MRD monitoring methods, the optimal time points for assessment, as well as different specimen types used. Additionally, it underscores the significance of MFC-MRD assessment in guiding the treatment of elderly AML.

Strategies to reduce relapse risk in patients undergoing allogeneic stem cell transplantation for acute myeloid leukaemia

Allogeneic stem cell transplantation is a centrally important curative strategy in adults with acute myeloid leukaemia; however, relapse occurs in a significant proportion of patients and remains the leading cause of treatment failure. The prognosis for patients who relapse post-transplant remains poor, and the development of new strategies with the ability to reduce disease recurrence without increasing transplant toxicity remains a priority. In this review, within the context of our understanding of disease biology and the graft-versus-leukaemia (GVL) effect, we will discuss established, evolving and novel approaches for increasing remission rates, decreasing measurable residual disease pretransplant, future methods to augment the GVL effect and the opportunities for post-transplant maintenance. Future progress depends upon the development of innovative trials and networks, which will ensure the rapid assessment of emerging therapies in prospective clinical trials.

Outcomes and prognosis of haploidentical haematopoietic stem cell transplantation in children with FLT3-ITD mutated acute myeloid leukaemia

The presence of internal tandem duplication mutations in the FMS-like tyrosine kinase 3 receptor (FLT3-ITD) is a poor prognostic predictor in paediatric patients with acute myeloid leukaemia (AML). We evaluated the treatment outcomes and prognostic factors of 45 paediatric patients with FLT3-ITD AML who achieved complete remission before haploidentical haematopoietic stem cell transplantation (haplo-HSCT) at our institution from 2012 to 2021. Among the 45 patients, the overall survival (OS), event‑free survival (EFS), and cumulative incidence of relapse (CIR) rates were 74.9% ± 6.6%, 64.1% ± 7.2%, and 31.4% ± 7.1%, respectively, with 48.8 months of median follow-up. Univariate and multivariate analyses associated positive minimal residual disease (MRD) at pre-HSCT and non-remission (NR) after introduce 1 with inferior long-term survival. The 100-day cumulative incidence of grade II-IV acute graft-versus-host disease (aGVHD) was 35.6% ± 5.2%, and that of grade III-IV aGVHD was 15.6% ± 3.0% The overall 4-year cumulative incidence of chronic graft-versus-host disease after transplantation was 35.7% ± 9.8%, respectively. In conclusion, haplo-HSCT may be a feasible strategy for paediatric patients with FLT3-ITD AML, and pre-HSCT MRD status and NR after introduce 1 significantly affected the outcomes.

Multi-gene measurable residual disease assessed by digital polymerase chain reaction has clinical and biological utility in acute myeloid leukemia patients receiving venetoclax/azacitidine

Venetoclax with azacitidine (ven/aza) is a lower-intensity therapeutic regimen that has been shown to improve outcomes in elderly patients with acute myeloid leukemia (AML). Measurable residual disease (MRD) using flow cytometry is a valuable tool for the prediction of relapse in AML using conventional therapies and ven/aza; however, the prognostic value for broadscale molecular MRD after ven/aza treatment is less clear. We aimed to determine the utility of retrospective assessment using multi-gene molecular MRD by droplet digital polymerase chain reaction (ddPCR). We found this approach correlates with outcomes in a cohort of patients receiving frontline ven/aza for AML. The predictive value of ddPCR MRD persisted when NPM1 mutations were removed from analysis, as well as after adjustment for the impact of stem cell transplant on outcomes. Late achievement of MRD negativity, including after SCT, was still associated with superior outcomes compared to persistently detectable MRD. We further explored the impact of ven/aza on the burden of different classes of mutations, and identified the persistence of splicing factor mutations, commonly associated with MDS, as a consistent finding after ven/aza treatment. These data add to our understanding of the effects of ven/aza on AML disease biology and provide details on molecular depth of remission that can guide prospective trials in the future.

Engineering the best transplant outcome for high-risk acute myeloid leukemia: the donor, the graft and beyond

Allogeneic hemopoietic cell transplantation remains the goal of therapy for high-risk acute myeloid leukemia (AML). However, treatment failure in the form of leukemia relapse or severe graft-versus-host disease remains a critical area of unmet need. Recently, significant progress has been made in the cell therapy-based interventions both before and after transplant. In this review, the Stem Cell Engineering Committee of the International Society for Cell and Gene Therapy summarizes the literature regarding the identification of high risk in AML, treatment approaches before transplant, optimal transplant platforms and measures that may be taken after transplant to ideally prevent, or, if need be, treat AML relapse. Although some strategies remain in the early phases of clinical investigation, they are built on progress in pre-clinical research and cellular engineering techniques that are already improving outcomes for children and adults with high-risk malignancies.

Survival after allogeneic transplantation according to pretransplant minimal residual disease and conditioning intensity in patients with acute myeloid leukemia

Background

The measurement of minimal residual disease (MRD) by multiparametric flow cytometry (MFC) before hematopoietic stem cell transplantation (HSCT) in patients with acute myeloid leukemia (AML) is a powerful prognostic factor. The interaction of pretransplant MRD and the conditioning intensity has not yet been clarified.

Objective

The aim of this study is to analyze the transplant outcomes of patients with AML who underwent HSCT in complete remission (CR), comparing patients with positive MRD (MRD+) and negative MRD (MRD-) before HSCT, and the interaction between conditioning intensity and pre-HSCT MRD.

Study design

We retrospectively analyzed the transplant outcomes of 118 patients with AML who underwent HSCT in CR in a single institution, comparing patients with MRD+ and MRD- before HSCT using a cutoff of 0.1% on MFC, and the interaction between conditioning intensity and pre-HSCT MRD.

Results

Patients with MRD+ before HSCT had a significantly worse 2-year (2y) event-free survival (EFS) (56.5% vs. 32.0%, p = 0.018) than MRD- patients, due to a higher cumulative incidence of relapse (CIR) at 2 years (49.0% vs. 18.0%, p = 0.002), with no differences in transplant-related mortality (TRM) (2y-TRM, 19.0% and 25.0%, respectively, p = 0.588). In the analysis stratified by conditioning intensity, in patients who received MAC, those with MRD- before HSCT had better EFS (p = 0.009) and overall survival (OS) (p = 0.070) due to lower CIR (p = 0.004) than MRD+ patients. On the other hand, the survival was similar in reduced intensity conditioning (RIC) patients regardless of the MRD status.

Conclusions

Patients with MRD+ before HSCT have worse outcomes than MRD- patients. In patients who received MAC, MRD- patients have better EFS and OS due to lower CIR than MRD+ patients, probably because they represent a more chemo-sensitive group. However, among RIC patients, results were similar regardless of the MRD status.

The RTK-RAS signaling pathway is enriched in patients with rare acute myeloid leukemia harboring t(16;21)(p11;q22)/FUS::ERG

Acute myeloid leukemia (AML) with t(16;21)(p11;q22)/FUS::ERG is a rare AML subtype associated with poor prognosis. However, its clinical and molecular features remain poorly defined. We determined the clinicopathological, genomic, and transcriptomic characteristics and outcomes of patients with AML harboring FUS::ERG at our center. Thirty-six AML patients harboring FUS::ERG were identified, with an incidence rate of 0.3%. These patients were characterized by high lactate dehydrogenase levels (median: 838.5 U/L), elevated bone marrow blast counts (median: 71.5%), and a CD56-positive immunophenotype (94.3%). Notably, we found that RTK-RAS GTPase (RAS) pathway genes, including NRAS (33%) and PTPN11 (24%), were frequently mutated in this subtype. Transcriptome analysis revealed enrichment of the phosphatidylinositol-3-kinase-Akt (PI3K-Akt), mitogen-activated protein kinase (MAPK), and RAS signaling pathways and upregulation of BCL2, the target of venetoclax, in FUS::ERG AML compared to RUNX1::RUNX1T1 AML, a more common AML subtype with good prognosis. The median event-free survival in patients with FUS::ERG AML was 11.9 (95% confidence interval [CI]: 9.0-not available [NA]) months and the median overall survival was 18.2 (95% CI: 12.4-NA) months. Allogeneic hematopoietic stem cell transplantation failed to improve outcomes. Overall, the high incidence of RTK-RAS pathway mutations and high expression of BCL2 may indicate promising therapeutic targets in this high-risk AML subset.

Allogeneic Hematopoietic Cell Transplantation in Advanced Systemic Mastocytosis: A retrospective analysis of the DRST and GREM registries

We identified 71 patients with AdvSM (aggressive SM [ASM], SM with an associated hematologic neoplasm [SM-AHN, e.g., acute myeloid leukemia, SM-AML], mast cell leukemia [MCL]) in two national registries (DRST/GREM) who received an allogeneic hematopoietic cell transplantation (alloHCT) performed in Germany from 1999-2021. Median overall survival (OS) of ASM/SM-AHN (n = 30, 45%), SM-AML (n = 28, 39%) and MCL ± AHN (n = 13, 19%) was 9.0, 3.3 and 0.9 years (P = 0.007). Improved median OS was associated with response of SM (17/41, 41%; HR 0.4 [0.2-0.9], P = 0.035) and/or of AHN (26/43, 60%, HR 0.3 [0.1-0.7], P = 0.004) prior to alloHCT. Adverse predictors for OS included absence of KIT D816V (10/61, 16%, HR 2.9 [1.2-6.5], P < 0.001) and a complex karyotype (9/60, 15%, HR 4.2 [1.8-10.0], P = 0.016). HLA-match, conditioning type or transplantation at centers reporting above-average alloHCTs (≥7) had no impact on OS. Taking into account competing events at years 1, 3 and 5, relapse-related mortality and non-relapse mortality rate were 15%/23%, 20%/30% and 23%/35%, respectively. Irrespective of subtype, subsequent treatment response was achieved in 13/30 (43%) patients and was highest on midostaurin/avapritinib (7/9, 78%). We conclude that outcome of alloHCT in AdvSM is more affected by disease phenotype and treatment response prior to transplant than by transplant characteristics.

Application of droplet digital PCR in minimal residual disease monitoring of rare fusion transcripts and mutations in haematological malignancies

Leukaemia of various subtypes are driven by distinct chromosomal rearrangement or genetic abnormalities. The leukaemogenic fusion transcripts or genetic mutations serve as molecular markers for minimal residual disease (MRD) monitoring. The current study evaluated the applicability of several droplet digital PCR assays for the detection of these targets at RNA and DNA levels (atypical BCR::ABL1 e19a2, e23a2ins52, e13a2ins74, rare types of CBFB::MYH11 (G and I), PCM1::JAK2, KMT2A::ELL2, PICALM::MLLT10 fusion transcripts and CEBPA frame-shift and insertion/duplication mutations) with high sensitivity. The analytical performances were assessed by the limit of blanks, limit of detection, limit of quantification and linear regression. Our data demonstrated serial MRD monitoring for patients at molecular level could become "digitalized", which was deemed important to guide clinicians in treatment decision for better patient care.

Biomarkers of minimal residual disease and treatment

Minimal residual disease (MRD) has been defined as a very small numbers of cancer cells that remain in the body after curative treatment. Its presence or absence will ultimately determine prognosis. With the introduction of new technologies the presence of MRD in patients with solid tumours can be detected and characterized. As MRD predicts future relapse, be it early or late treatment failure, in an otherwise asymptomatic patient its treatment and when to start treatment remains to be determined. Thus the concepts of personalized medicine using different biomarkers to classify the biological properties of MRD maybe come possible. Based on this determinations it may be possible to use targeted therapies rather than all patients with the same type of cancer receiving a standard treatment. However, it is important to understand the limitations of the different technologies, what these techniques are detecting and how they may help in the treatment of patients with cancer. The majority of published studies are in patients with metastatic cancer and there are few reports in patients with MRD. In this chapter the concept of MRD, the methods used to detect it and what treatments may be effective based on the biological characteristics of the tumour cells as determined by different biomarkers is reviewed. MRD depends on the phenotypic properties of the tumour cells to survive in their new environment and the anti-tumour immune response. This is a dynamic process and changes with time in the wake of immunosuppression caused by the tumour cells and/or the effects of treatment to select resistant tumour cells. With the use of biomarkers to typify the characteristics of MRD and the development of new drugs a personalized treatment can be designed rather than all patients given the same treatment. Patients who are initially negative for MRD may not require further treatment with liquid biopsies used to monitor the patients during follow-up in order to detect those patients who may become MRD positive. The liquid biopsy used during the follow up of MRD positive patients can be used to detect changes in the biological properties of the tumour cells and thus may need treatment changes to overcome tumour cell resistance.

Minimal Residual Disease in Acute Myeloid Leukemia: Old and New Concepts

Minimal residual disease (MRD) is of major importance in onco-hematology, particularly in acute myeloid leukemia (AML). MRD measures the amount of leukemia cells remaining in a patient after treatment, and is an essential tool for disease monitoring, relapse prognosis, and guiding treatment decisions. Patients with a negative MRD tend to have superior disease-free and overall survival rates. Considerable effort has been made to standardize MRD practices. A variety of techniques, including flow cytometry and molecular methods, are used to assess MRD, each with distinct strengths and weaknesses. MRD is recognized not only as a predictive biomarker, but also as a prognostic tool and marker of treatment efficacy. Expected advances in MRD assessment encompass molecular techniques such as NGS and digital PCR, as well as optimization strategies such as unsupervised flow cytometry analysis and leukemic stem cell monitoring. At present, there is no perfect method for measuring MRD, and significant advances are expected in the future to fully integrate MRD assessment into the management of AML patients.

Long-term follow-up of haploidentical haematopoietic stem cell transplantation in paediatric patients with high-risk acute myeloid leukaemia: Report from a single centre

Data from 200 children with high-risk acute myeloid leukaemia who underwent their first haploidentical haematopoietic stem cell transplantation (haplo-HSCT) between 2015 and 2021 at our institution were analysed. The 4-year overall survival (OS), event-free survival (EFS) and cumulative incidence of relapse (CIR) were 71.9%, 62.3% and 32.4% respectively. The 100-day cumulative incidences of grade II-IV and III-IV acute graft-versus-host disease (aGVHD) were 41.1% and 9.5% respectively. The 4-year cumulative incidence of chronic GVHD (cGVHD) was 56.1%, and that of moderate-to-severe cGVHD was 27.3%. Minimal residual disease (MRD)-positive (MRD+) status pre-HSCT was significantly associated with lower survival and a higher risk of relapse. The 4-year OS, EFS and CIR differed significantly between patients with MRD+ pre-HSCT (n = 97; 63.4%, 51.4% and 41.0% respectively) and those with MRD-negative (MRD-) pre-HSCT (n = 103; 80.5%, 73.3% and 23.8% respectively). Multivariate analysis also revealed that acute megakaryoblastic leukaemia without Down syndrome (non-DS-AMKL) was associated with extremely poor outcomes (hazard ratios and 95% CIs for OS, EFS and CIR: 3.110 (1.430-6.763), 3.145 (1.628-6.074) and 3.250 (1.529-6.910) respectively; p-values were 0.004, 0.001 and 0.002 respectively). Thus, haplo-HSCT can be a therapy option for these patients, and MRD status pre-HSCT significantly affects the outcomes. As patients with non-DS-AMKL have extremely poor outcomes, even with haplo-HSCT, a combination of novel therapies is urgently needed.

Measurable residual disease conversion rate with consolidation chemotherapy in acute myeloid leukemia

The rate of MRD clearance in AML with standard consolidation chemotherapy is not well defined. A multi-institution retrospective analysis was performed on 107 consecutively treated AML patients in morphologic complete remission with detectable MRD post-induction therapy who received standard chemotherapy consolidation. In response to standard intermediate/high-dose cytarabine consolidation therapy, 26 of 60 patients (43.3%) with MRD threshold of detection of at least 0.1% converted to MRD-negative status (undetectable with assay used), and 6 of 47 patients (12.8%) with MRD threshold of detection > 0.1% converted to MRD-negative status. Multivariable logistic regression for patients with MRD threshold of detection of at least 0.1% showed that, when controlling for age, ELN risk category, dose of cytarabine, and use of a combination agent, treatment with 1 cycle of consolidation cytarabine versus ≥2 cycles decreased the odds of conversion of AML to MRD-negative (OR = 0.24, 95% CI 0.07-0.85, p = 0.03).

Long-term follow-up of patients with acute myeloid leukemia undergoing allogeneic hematopoietic stem cell transplantation after primary induction failure

Primary induction failure (PIF) in acute myeloid leukemia (AML) patients is associated with poor outcome, with allogeneic hematopoietic stem cell transplantation (HCT) being the sole curative therapeutic option. Here, we retrospectively evaluated long-term outcomes of 220 AML patients undergoing allogeneic HCT after PIF who never achieved remission, and identified clinical and molecular risk factors associated with treatment response and ultimate prognosis. In this high-risk population, disease-free survival was 25.2% after 5 years and 18.7% after 10 years, while overall survival rates were 29.8% and 21.6% after 5 and 10 years of HCT, respectively. 10-year non-relapse mortality was 32.5%, and 48.8% of patients showed disease relapse within 10 years after allogeneic HCT. Adverse molecular risk features determined at initial diagnosis, poor performance status at the time of allogeneic HCT, and long diagnosis-to-HCT intervals were associated with unfavorable prognosis. Collectively, our data suggests that immediate allogeneic HCT after PIF offers long-term survival and cure in a substantial subset of cases and that high-risk AML patients who never achieved complete response during induction might benefit from early donor search.

Test Then Erase? Current Status and Future Opportunities for Measurable Residual Disease Testing in Acute Myeloid Leukemia

BACKGROUND

Measurable residual disease (MRD) test positivity during and after treatment in patients with acute myeloid leukemia (AML) has been associated with higher rates of relapse and worse overall survival. Current approaches for MRD testing are not standardized leading to inconsistent results and poor prognostication of disease. Pertinent studies evaluating AML MRD testing at specific times points, with various therapeutics and testing methods are presented.

SUMMARY

AML is a set of diseases with different molecular and cytogenetic characteristics and is often polyclonal with evolution over time. This genetic diversity poses a great challenge for a single AML MRD testing approach. The current ELN 2021 MRD guidelines recommend MRD testing by quantitative polymerase chain reaction in those with a validated molecular target or multiparameter flow cytometry (MFC) in all other cases. The benefit of MFC is the ability to use this method across disease subsets, at the relative expense of suboptimal sensitivity and specificity. AML MRD detection may be improved with molecular methods. Genetic characterization at AML diagnosis and relapse is now standard of care for appropriate therapeutic assignment, and future initiatives will provide the evidence to support testing in remission to direct clinical interventions.

KEY MESSAGES

The treatment options for patients with AML have expanded for specific molecular subsets such as FLT3 and IDH1/2 mutated AML, with development of novel agents for NPM1 mutated or KMT2A rearranged AML ongoing, but also due to effective venetoclax-combinations. Evidence regarding highly sensitive molecular MRD detection methods for specific molecular subgroups, in the context of these new treatment approaches, will likely shape the future of AML care.

Optimal Post-Remission Consolidation Therapy in Patients with AML

BACKGROUND

Despite recent advances, 40-85% of patients with acute myeloid leukaemia (AML) achieve complete remission after intensive chemotherapy. However, without optimal treatment after remission, the risk of relapse remains high.

SUMMARY

A variable number of consolidation cycles consisting of intermediate doses of cytarabine are the most commonly used regimens in low-intermediate-risk AML, while patients at higher risk of relapse should consolidate response by proceeding to HSCT. Different post-consolidation (maintenance therapies) have demonstrated their benefit in prolonging relapse-free survival, and others are still under investigation. Careful consideration should be given to which patients benefit most from each of these interventions, considering that the risk of relapse is dynamic.

KEY MESSAGES

Patients consolidated with chemotherapy should receive either 2 courses of HDAC or no more than 3-4 cycles of IDAC with dose reduction in patients over 60 years. Patients with mutated FLT3 AML benefit from post-consolidation maintenance with FLT3 inhibitors, and selected patients not fit for adequate consolidation may benefit from CC-468 maintenance. Patients at higher risk of relapse should proceed to allogeneic SCT as soon as possible, opting for a more intensive conditioning in patients younger than 55 years. However, autologous HSCT may still have role in favourable-risk MRD-negative AML. Multiple treatment options targeting MRD are emerging, either as definitive treatment or as a bridge to allogeneic transplantation, and are likely to become increasingly relevant.

Recent advances in allogeneic transplantation for acute myeloid leukemia

PURPOSE OF REVIEW

This review highlights recent advancements in allogeneic hematopoietic stem cell transplantation (allo-HSCT) for patients with acute myeloid leukemia (AML).

RECENT FINDINGS

Important improvements have been observed throughout the allo-HSCT procedure and patient management. Universal donor availability and reduced risk of graft-versus-host disease (GVHD) have been achieved with the introduction of posttransplant cyclophosphamide for GVHD prophylaxis. It has contributed, together with advances in conditioning regimens, GVHD treatment and supportive care, to a reduced overall toxicity of the procedure. Relapse is now the most frequent cause of transplant failure. With increased knowledge of the biological characterization of AML, better prediction of transplant risks and more profound and standardized minimal residual disease (MRD) monitoring, pharmacological, and immunological strategies to prevent relapse are been developed.

SUMMARY

Allo-HSCT remains the standard of care for high-risk AML. Increased access to transplant, reduced toxicity and relapse are improving patient outcomes. Further research is needed to optimize MRD monitoring, refine conditioning regimens, and explore new GVHD management and relapse prevention therapies.

The core concepts of core binding factor acute myeloid leukemia: Current considerations for prognosis and treatment

Core binding factor acute myeloid leukemia (CBF AML), defined by t(8;21) or inv(16), is a subset of favorable risk AML. Despite its association with a high complete remission rate after induction and relatively good prognosis overall compared with other subtypes of AML, relapse risk after induction chemotherapy remains high. Optimizing treatment planning to promote recurrence free survival and increase the likelihood of survival after relapse is imperative to improving outcomes. Recent areas of research have included evaluation of the role of gemtuzumab in induction and consolidation, the relative benefit of increased cycles of high dose cytarabine in consolidation, the utility of hypomethylating agents and kinase inhibitors, and the most appropriate timing of stem cell transplant. Surveillance with measurable residual disease testing is increasingly being utilized for monitoring disease in remission, and ongoing investigation seeks to determine how to use this tool for early identification of patients who would benefit from proceeding to transplant. In this review, we outline the current therapeutic approach from diagnosis to relapse while highlighting the active areas of investigation in each stage of treatment.