Blinatumomab differentially modulates peripheral blood and bone marrow immune cell repertoire: A Campus ALL study.

Blinatumomab is the first bi-specific T-cell engager approved for relapsed or refractory B-cell precursor acute lymphoblastic leukaemia (B-ALL). Despite remarkable clinical results, the effects of blinatumomab on the host immune cell repertoire are not fully elucidated. In the present study, we characterized the peripheral blood (PB) and, for the first time, the bone marrow (BM) immune cell repertoire upon blinatumomab treatment. Twenty-nine patients with B-ALL received blinatumomab according to clinical practice. Deep multiparametric flow cytometry was used to characterize lymphoid subsets during the first treatment cycle. Blinatumomab induced a transient redistribution of PB effector T-cell subsets and Treg cells with a persistent increase in cytotoxic NK cells, which was associated with a transient upregulation of immune checkpoint receptors on PB CD4 and CD8 T-cell subpopulations and of CD39 expression on suppressive Treg cells. Of note, BM immune T-cell subsets showed a broader post-treatment subversion, including the modulation of markers associated with a T-cell-exhausted phenotype. In conclusion, our study indicates that blinatumomab differentially modulates the PB and BM immune cell repertoire, which may have relevant clinical implications in the therapeutic setting.

Incidence, treatment and outcome of central nervous system relapse in adult acute lymphoblastic leukaemia patients treated front-line with paediatric-inspired regimens: A retrospective multicentre Campus ALL study.

Within the Campus ALL network we analyzed the incidence, characteristics, treatment and outcome of a central nervous system (CNS) relapse in 1035 consecutive adult acute lymphoblastic leukemia (ALL) patients treated frontline with pediatric-inspired protocols between 2009 and 2020. Seventy-one patients (6.8%) experienced a CNS recurrence, more frequently in T- (28/278; 10%) than in B-ALL (43/757; 5.7%) (p = 0.017). An early CNS relapse-< 12 months from diagnosis-was observed in 41 patients. In multivariate analysis, risk factors for early CNS relapse included T-cell phenotype (p = <0.001), hyperleucocytosis >100 × 109 /L (p<0.001) and male gender (p = 0.015). Treatment was heterogeneous, including chemotherapy, radiotherapy, intrathecal therapy and novel agents. A complete remission (CR) was obtained in 39 patients (55%) with no differences among strategies. After CR, 26 patients underwent an allogenic transplant, with a significant overall survival benefit compared to non-transplanted patients (p = 0.012). After a median observation of 8 months from CNS relapse, 23 patients (32%) were alive. In multivariate analysis, the time to CNS relapse was the strongest predictor of a lower 2-year post-relapse survival (p<0.001). In conclusion, in adult ALL the outcome after a CNS relapse remains very poor. Effective CNS prophylaxis remains the best approach and allogenic transplant should be pursued when possible.

Multicenter retrospective analysis of clinical outcome of adult patients with mixed-phenotype acute leukemia treated with acute myeloid leukemia-like or acute lymphoblastic leukemia-like chemotherapy and impact of allogeneic stem cell transplantation: a Campus ALL study.

Mixed-phenotype acute leukemia (MPAL) is a rare disease. Treatment is often similar to that of acute lymphoblastic leukemia (ALL), but the outcome in adults and the role of allogeneic stem cell transplantation (AlloSCT) are not well defined. We report on 77 adult patients diagnosed with MPAL over the last 10 years and treated with a curative intent. Median age was 49 years; 7.6% of cases had a BCR::ABL1 rearrangement. Thirty patients (39%) were treated with an acute myeloid leukemia (AML)-like induction and 47 (61%) with an ALL-like scheme. The complete remission (CR) rate was 67.6% and an ALL-like therapy was associated with a better CR rate (P = 0.048). The median OS was 41.9 months; age ≤ 60 years was associated with a better OS (67 vs 26 months, P = 0.014). An AlloSCT was performed in 50 patients (65%). The 5-year OS of transplanted patients was 54%. The OS post-AlloSCT was better in patients who were minimal residual disease (MRD)-negative prior to transplant (75.8% vs 45.2%, P = 0.06). This study shows that MPAL patients respond better to an ALL-like induction therapy; that consolidation therapy should include, whenever possible, an AlloSCT and that MRD negativity should be a primary endpoint of treatment.

Genomic and clinical findings in myeloid neoplasms with PDGFRB rearrangement.

Platelet-derived growth factor receptor B (PDGFRB) gene rearrangements define a unique subgroup of myeloid and lymphoid neoplasms frequently associated with eosinophilia and characterized by high sensitivity to tyrosine kinase inhibition. To date, various PDGFRB/5q32 rearrangements, involving at least 40 fusion partners, have been reported. However, information on genomic and clinical features accompanying rearrangements of PDGFRB is still scarce. Here, we characterized a series of 14 cases with a myeloid neoplasm using cytogenetic, single nucleotide polymorphism array, and next-generation sequencing. We identified nine PDGFRB translocation partners, including the KAZN gene at 1p36.21 as a novel partner in a previously undescribed t(1;5)(p36;q33) chromosome change. In all cases, the PDGFRB recombination was the sole cytogenetic abnormality underlying the phenotype. Acquired somatic variants were mainly found in clinically aggressive diseases and involved epigenetic genes (TET2, DNMT3A, ASXL1), transcription factors (RUNX1 and CEBPA), and signaling modulators (HRAS). By using both cytogenetic and nested PCR monitoring to evaluate response to imatinib, we found that, in non-AML cases, a low dosage (100-200 mg) is sufficient to induce and maintain longstanding hematological, cytogenetic, and molecular remissions.

The Role of T Cell Immunity in Monoclonal Gammopathy and Multiple Myeloma: From Immunopathogenesis to Novel Therapeutic Approaches.

Multiple Myeloma (MM) is a malignant growth of clonal plasma cells, typically arising from asymptomatic precursor conditions, namely monoclonal gammopathy of undetermined significance (MGUS) and smoldering MM (SMM). Profound immunological dysfunctions and cytokine deregulation are known to characterize the evolution of the disease, allowing immune escape and proliferation of neoplastic plasma cells. In the past decades, several studies have shown that the immune system can recognize MGUS and MM clonal cells, suggesting that anti-myeloma T cell immunity could be harnessed for therapeutic purposes. In line with this notion, chimeric antigen receptor T cell (CAR-T) therapy is emerging as a novel treatment in MM, especially in the relapsed/refractory disease setting. In this review, we focus on the pivotal contribution of T cell impairment in the immunopathogenesis of plasma cell dyscrasias and, in particular, in the disease progression from MGUS to SMM and MM, highlighting the potentials of T cell-based immunotherapeutic approaches in these settings.

Do high MICs predict the outcome in invasive fusariosis?

BACKGROUND: Invasive fusariosis (IF) affects mostly severely immunocompromised hosts and is associated with poor outcome. Since Fusarium species exhibit high MICs for most antifungal agents, this could explain the poor prognosis. However, a clear-cut correlation between MIC and outcome has not been established. OBJECTIVE: To evaluate the correlation between MIC and outcome (6 week death rate) in patients with IF. METHODS: We performed a multicentre retrospective study of patients with IF who received treatment and had MIC levels determined by EUCAST or CLSI for the drug(s) used during treatment. We compared the MIC50 and MIC distribution among survivors and patients who died within 6 weeks from the diagnosis of IF. RESULTS: Among 88 patients with IF, 74 had haematological diseases. Primary treatment was monotherapy in 52 patients (voriconazole in 27) and combination therapy in 36 patients (liposomal amphotericin B + voriconazole in 23). The MIC50 and range for the five most frequent agents tested were: voriconazole 8 mg/L (range 0.5-64), amphotericin B 2 mg/L (range 0.25-64), posaconazole 16 mg/L (range 0.5-64), itraconazole 32 mg/L (range 4-64), and isavuconazole 32 mg/L (range 8-64). There was no difference in MIC50 and MIC distribution among survivors and patients who died. By contrast, persistent neutropenia and receipt of corticosteroids were strong predictors of 6 week mortality. CONCLUSIONS: Our study did not show any correlation between MIC and mortality at 6 weeks in patients with IF.

Cytomegalovirus reactivation after hematopoietic stem cell transplant with CMV-IG prophylaxis: A monocentric retrospective analysis.

Human cytomegalovirus (CMV) represents the most common viral infection after hematopoietic stem cell transplant (HSCT), mainly occurring as reactivation from latency in seropositive patients, with a different prevalence based on the extent and timing of seroconversion in a specific population. Here, we retrospectively analyzed a cohort of patients who underwent HSCT at our Institution between 2013 and 2018, all of whom were prophylactically treated with CMV-IG (Megalotect Biotest®), to define the incidence and clinical outcomes of CMV reactivation and clinically significant infection. CMV infection occurred in 69% of our patient series, mainly resulting from reactivation, and CMV clinically significant infection (CS-CMVi) occurred in 48% of prophylactically treated patients. CMV infection and CS-CMVi impacted neither on relapse incidence nor on overall survival nor on relapse-free survival. Moreover, a very low incidence of CMV end-organ disease was documented. CMV-IG used alone as prophylactic therapy after HSCT does not effectively prevent CMV reactivation.

Clinical significance of occult central nervous system disease in adult acute lymphoblastic leukemia. A multicenter report from the Campus ALL Network.

In acute lymphoblastic leukemia, flow cytometry detects more accurately leukemic cells in patients' cerebrospinal fluid compared to conventional cytology. However, the clinical significance of flow cytometry positivity with a negative cytology - occult central nervous system disease - is not clear. In the framework of the national Campus ALL program, we retrospectively evaluated the incidence of occult central nervous system disease and its impact on outcome in 240 adult patients with newly diagnosed acute lymphoblastic leukemia. All cerebrospinal fluid samples were investigated by conventional cytology and flow cytometry. The presence of ≥10 phenotypically abnormal events, forming a cluster, was considered as flow cytometry positivity. No central nervous system involvement was documented in 179 patients, while 18 were positive by conventional morphology and 43 were occult central nervous system disease positive. The relapse rate was significantly lower in central nervous system disease negative patients and the disease-free and overall survival were significantly longer in central nervous system disease negative patients than in those with manifest or occult central nervous system disease positive. In multivariate analysis, the status of manifest and occult central nervous system disease positivity was independently associated with a worse overall survival. In conclusion, we demonstrate that in adult acute lymphoblastic leukemia patients at diagnosis flow cytometry can detect occult central nervous system disease at high sensitivity and that the status of occult central nervous system disease positivity is associated with an adverse outcome. (Clinicaltrials.gov NCT03803670).

Neoantigen-Specific T-Cell Immune Responses: The Paradigm of NPM1-Mutated Acute Myeloid Leukemia.

The C-terminal aminoacidic sequence from NPM1-mutated protein, absent in normal human tissues, may serve as a leukemia-specific antigen and can be considered an ideal target for NPM1-mutated acute myeloid leukemia (AML) immunotherapy. Different in silico instruments and in vitro/ex vivo immunological platforms have identified the most immunogenic epitopes from NPM1-mutated protein. Spontaneous development of endogenous NPM1-mutated-specific cytotoxic T cells has been observed in patients, potentially contributing to remission maintenance and prolonged survival. Genetically engineered T cells, namely CAR-T or TCR-transduced T cells, directed against NPM1-mutated peptides bound to HLA could prospectively represent a promising therapeutic approach. Although either adoptive or vaccine-based immunotherapies are unlikely to be highly effective in patients with full-blown leukemia, these strategies, potentially in combination with immune-checkpoint inhibitors, could be promising in maintaining remission or preemptively eradicating persistent measurable residual disease, mainly in patients ineligible for allogeneic hematopoietic stem cell transplant (HSCT). Alternatively, neoantigen-specific donor lymphocyte infusion derived from healthy donors and targeting NPM1-mutated protein to selectively elicit graft-versus-leukemia effect may represent an attractive option in subjects experiencing post-HSCT relapse. Future studies are warranted to further investigate dynamics of NPM1-mutated-specific immunity and explore whether novel individualized immunotherapies may have potential clinical utility in NPM1-mutated AML patients.

Inflammatory Microenvironment and Specific T Cells in Myeloproliferative Neoplasms: Immunopathogenesis and Novel Immunotherapies.

The Philadelphia-negative myeloproliferative neoplasms (MPNs) are malignancies of the hematopoietic stem cell (HSC) arising as a consequence of clonal proliferation driven by somatically acquired driver mutations in discrete genes (JAK2, CALR, MPL). In recent years, along with the advances in molecular characterization, the role of immune dysregulation has been achieving increasing relevance in the pathogenesis and evolution of MPNs. In particular, a growing number of studies have shown that MPNs are often associated with detrimental cytokine milieu, expansion of the monocyte/macrophage compartment and myeloid-derived suppressor cells, as well as altered functions of T cells, dendritic cells and NK cells. Moreover, akin to solid tumors and other hematological malignancies, MPNs are able to evade T cell immune surveillance by engaging the PD-1/PD-L1 axis, whose pharmacological blockade with checkpoint inhibitors can successfully restore effective antitumor responses. A further interesting cue is provided by the recent discovery of the high immunogenic potential of JAK2V617F and CALR exon 9 mutations, that could be harnessed as intriguing targets for innovative adoptive immunotherapies. This review focuses on the recent insights in the immunological dysfunctions contributing to the pathogenesis of MPNs and outlines the potential impact of related immunotherapeutic approaches.

Nelarabine as salvage therapy and bridge to allogeneic stem cell transplant in 118 adult patients with relapsed/refractory T-cell acute lymphoblastic leukemia/lymphoma. A CAMPUS ALL study.

The outcome of relapsed or refractory (R/R) T-cell acute lymphoblastic leukemia/lymphoma (T-ALL/T-LBL) in adults is poor, with less than 20% of patients surviving at 5 years. Nelarabine is the only drug specifically approved for R/R T-ALL/T-LBL, but the information to support its use is based on limited available data. The aim of this observational phase four study was to provide recent additional data on the efficacy and safety of nelarabine in adults with R/R T-ALL/T-LBL and to evaluate the feasibility and outcome of allogeneic hematopoietic stem cell transplant (SCT) after salvage with nelarabine therapy. The primary endpoints were overall response rate (ORR) and overall survival (OS). Additional endpoints were safety, SCT rate and post-SCT OS. Between May 2007 and November 2018, 118 patients received nelarabine salvage therapy at 27 Italian hematology sites. The median age was 37 years (range 18-74 years), 73% were male, 77 had a diagnosis of T-ALL and 41 of T-LBL, and 65/118 (55%) had received more than two lines of therapy. The median number of nelarabine cycles was two (range 1-4); 43/118 (36%) patients had complete remission (CR), 16 had partial remission (14%) and 59 (50%) were refractory, with an ORR of 50%. The probability of OS, from the first dose of nelarabine, was 37% at 1 year with a median survival of 8 months. The OS at 1 year was significantly better for the 47 patients (40%) who underwent SCT after nelarabine salvage therapy (58% vs 22%, log-rank P < .001). The probability of OS at 2 and 5 years from SCT was 46% and 38%, respectively. Seventy-five patients (64%) experienced one or more drug-related adverse events (AE). Grade III-IV neurologic toxicities were observed in 9/118 (8%) of cases and thrombocytopenia or/and neutropenia (grade III-IV) were reported in 41% and 43% of cases, respectively. In conclusion, this is one of the largest cohorts of adult patients with R/R T-ALL/T-LBL treated in real life with nelarabine. Taking into account the poor prognosis of this patient population, nelarabine represents an effective option with an ORR of 50% and a CR rate of 36%. In addition, 40% of cases following nelarabine salvage therapy could undergo SCT with an expected OS at 2 and 5 years of 46% and 38%, respectively. The safety profile of nelarabine was acceptable with only 8% of cases showing grade III-IV neurological AE.

Investigating the association between physicians self-efficacy regarding communication skills and risk of "burnout".

BACKGROUND: Breaking bad news (BBN) may be associated with increasing risk of burnout in practising physicians. However, there is little research on the association between the way bad news is broken and burnout. We investigated the association between physicians' self-efficacy regarding communication to patients and risk of burnout. METHODS: We performed a cross-sectional study by proposing an ad-hoc survey exploring attitudes and practice regarding BBN and the Maslach Burnout Inventory - Human Service Survey to 379 physicians from two University Hospitals in Italy. Associations were assessed by multivariable logistic regression models. RESULTS: Two-hundred twenty-six (60%) physicians returned the questionnaires. 76% of physicians acquired communication skills by observing mentors or colleagues, 64% considered BBN as discussing a poor prognosis, 56% reported discussing prognosis as the most difficult task, 38 and 37% did not plan a BBN encounter and considered it stressful. The overall burnout rate was 59%. Considering BBN a stressful task was independently associated with high risk of burnout (OR 3.01; p = 0.013). Planning the encounter (OR = 0.43, p = 0.037), mastering communication skills (OR = 0.19, p = 0.034) and the self-evaluation as good or very good at BBN (OR 0.32; 0.15 to 0.71; p = 0.0) were associated with low risk of burnout. CONCLUSIONS: Our findings suggest that some physicians' BBN attitudes and knowledge of conceptual frameworks may influence the risk of burnout and support the notion that increasing knowledge about communication skills may protect clinicians from burnout. Further research is needed in this area.

NPM1-Mutated Myeloid Neoplasms with <20% Blasts: A Really Distinct Clinico-Pathologic Entity?

Nucleophosmin (NPM1) gene mutations rarely occur in non-acute myeloid neoplasms (MNs) with <20% blasts. Among nearly 10,000 patients investigated so far, molecular analyses documented NPM1 mutations in around 2% of myelodysplastic syndrome (MDS) cases, mainly belonging to MDS with excess of blasts, and 3% of myelodysplastic/myeloproliferative neoplasm (MDS/MPN) cases, prevalently classified as chronic myelomonocytic leukemia. These uncommon malignancies are associated with an aggressive clinical course, relatively rapid progression to overt acute myeloid leukemia (AML) and poor survival outcomes, raising controversies on their classification as distinct clinico-pathologic entities. Furthermore, fit patients with NPM1-mutated MNs with <20% blasts could benefit most from upfront intensive chemotherapy for AML rather than from moderate intensity MDS-directed therapies, although no firm conclusion can currently be drawn on best therapeutic approaches, due to the limited available data, obtained from small and mainly retrospective series. Caution is also suggested in definitely diagnosing NPM1-mutated MNs with blast count <20%, since NPM1-mutated AML cases frequently present dysplastic features and multilineage bone marrow cells showing abnormal cytoplasmic NPM1 protein delocalization by immunohistochemical staining, therefore belonging to NPM1-mutated clone regardless of blast morphology. Further prospective studies are warranted to definitely assess whether NPM1 mutations may become sufficient to diagnose AML, irrespective of blast percentage.

Acute Myeloid Leukemia in Patients Living with HIV Infection: Several Questions, Fewer Answers.

Both human immunodeficiency virus (HIV) infection and acute myeloid leukemia (AML) may be considered relatively uncommon disorders in the general population, but the precise incidence of AML in people living with HIV infection (PLWH) is uncertain. However, life expectancy of newly infected HIV-positive patients receiving anti-retroviral therapy (ART) is gradually increasing, rivaling that of age-matched HIV-negative individuals, so that the occurrence of AML is also expected to progressively increase. Even if HIV is not reported to be directly mutagenic, several indirect leukemogenic mechanisms, mainly based on bone marrow microenvironment disruption, have been proposed. Despite a well-controlled HIV infection under ART should no longer be considered per se a contraindication to intensive chemotherapeutic approaches, including allogeneic hematopoietic stem cell transplantation, in selected fit patients with AML, survival outcomes are still generally unsatisfactory. We discussed several controversial issues about pathogenesis and clinical management of AML in PLWH, but few evidence-based answers may currently be provided, due to the limited number of cases reported in the literature, mainly as case reports or small retrospective case series. Prospective multicenter clinical trials are warranted to more precisely investigate epidemiology and cytogenetic/molecular features of AML in PLWH, but also to standardize and further improve its therapeutic management.

BCR-ABL-specific T-cell therapy in Ph+ ALL patients on tyrosine-kinase inhibitors.

Although the emergence of bone marrow (BM)-resident p190BCR-ABL-specific T lymphocytes has been correlated with hematologic and cytogenetic remissions in patients with Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) undergoing maintenance tyrosine-kinase inhibitor treatment, little is known about the possibility of culturing these cells ex vivo and using them in T-cell therapy strategies. We investigated the feasibility of expanding/priming p190BCR-ABL-specific T cells in vitro by stimulation with dendritic cells pulsed with p190BCR-ABL peptides derived from the BCR-ABL junctional region and alternative splicing, and of adoptively administering them to patients with relapsed disease. We report on the feasibility of producing clinical-grade BCR-ABL-specific cytotoxic T lymphocytes (CTLs), endowed with antileukemia activity, from Ph+ ALL patients and healthy donors. We treated 3 patients with Ph+ ALL with autologous or allogeneic p190BCR-ABL-specific CTLs. No postinfusion toxicity was observed, except for a grade II skin graft-versus-host disease in the patient treated for hematologic relapse. All patients achieved a molecular or hematologic complete remission (CR) after T-cell therapy, upon emergence of p190BCR-ABL-specific T cells in the BM. Our results show that p190BCR-ABL-specific CTLs are capable of controlling treatment-refractory Ph+ ALL in vivo, and support the development of adoptive immunotherapeutic approaches with BCR-ABL CTLs in Ph+ ALL.

Mutational landscape of patients with acute promyelocytic leukemia at diagnosis and relapse.

Despite the high probability of cure of patients with acute promyelocytic leukemia (APL), mechanisms of relapse are still largely unclear. Mutational profiling at diagnosis and/or relapse may help to identify APL patients needing frequent molecular monitoring and early treatment intervention. Using an NGS approach including a 31 myeloid gene-panel, we tested BM samples of 44 APLs at the time of diagnosis, and of 31 at relapse. Mutations in PML and RARA genes were studied using a customized-NGS-RNA panel. Patients relapsing after ATRA-chemotherapy rarely had additional mutations (P = .009). In patients relapsing after ATRA/ATO, the PML gene was a preferential mutation target. We then evaluated the predictive value of mutations at APL diagnosis. A median of two mutations was detectable in 9/11 patients who later relapsed, vs one mutation in 21/33 patients who remained in CCR (P = .0032). This corresponded to a significantly lower risk of relapse in patients with one or less mutations (HR 0.046; 95% CI 0.011-0.197; P < .0001). NGS-analysis at the time of APL diagnosis may inform treatment decisions, including alternative treatments for cases with an unfavorable mutation profile.

Outcomes of patients with invasive fusariosis who undergo further immunosuppressive treatments, is there a role for secondary prophylaxis?

BACKGROUND: Patients treated for invasive aspergillosis may relapse during subsequent periods of immunosuppression and should receive secondary prophylaxis. Little is known about the frequency of relapse and practices of secondary prophylaxis for invasive fusariosis (IF). OBJECTIVES: Evaluate practices of secondary prophylaxis and the frequency of relapse in patients who survived IF and were exposed to subsequent periods of immunosuppression. METHODS: Multicentre retrospective study of patients with haematological malignancies who developed IF, survived the initial fungal disease period, and were exposed to subsequent periods of immunosuppression. RESULTS: Among 40 patients, 35 received additional chemotherapy and developed neutropenia (median, 24 days; range, 4-104), and five received glucocorticoids for the treatment of graft-vs-host disease. Overall, 32 patients received secondary prophylaxis (voriconazole in 24) for a median of 112 days (range, 12-468). IF relapsed in five patients (12.5%): 2/8 (25%) not on prophylaxis and 3/32 (9.4%) receiving prophylaxis. Among 28 patients with disseminated IF, relapse occurred in 2/2 (100%) not on prophylaxis and in 3/26 (11.5%) on prophylaxis (P = 0.03). All patients who relapsed IF died. CONCLUSIONS: Patients with IF who survive the initial disease may relapse if exposed to subsequent episodes of immunosuppressive therapies. Secondary prophylaxis should be considered, especially if IF was disseminated.

Minimal/Measurable Residual Disease Monitoring in NPM1-Mutated Acute Myeloid Leukemia: A Clinical Viewpoint and Perspectives.

Acute myeloid leukemia (AML) with NPM1 gene mutations is currently recognized as a distinct entity, due to its unique biological and clinical features. We summarize here the results of published studies investigating the clinical application of minimal/measurable residual disease (MRD) in patients with NPM1-mutated AML, receiving either intensive chemotherapy or hematopoietic stem cell transplantation. Several clinical trials have so far demonstrated a significant independent prognostic impact of molecular MRD monitoring in NPM1-mutated AML and, accordingly, the Consensus Document from the European Leukemia Net MRD Working Party has recently recommended that NPM1-mutated AML patients have MRD assessment at informative clinical timepoints during treatment and follow-up. However, several controversies remain, mainly with regard to the most clinically significant timepoints and the MRD thresholds to be considered, but also with respect to the optimal source to be analyzed, namely bone marrow or peripheral blood samples, and the correlation of MRD with other known prognostic indicators. Moreover, we discuss potential advantages, as well as drawbacks, of newer molecular technologies such as digital droplet PCR and next-generation sequencing in comparison to conventional RQ-PCR to quantify NPM1-mutated MRD. In conclusion, further prospective clinical trials are warranted to standardize MRD monitoring strategies and to optimize MRD-guided therapeutic interventions in NPM1-mutated AML patients.