2021 Update on MRD in acute myeloid leukemia: a consensus document from the European LeukemiaNet MRD Working Party.

Measurable residual disease (MRD) is an important biomarker in acute myeloid leukemia (AML) that is used for prognostic, predictive, monitoring, and efficacy-response assessments. The European LeukemiaNet (ELN) MRD Working Party evaluated standardization and harmonization of MRD in an ongoing manner and has updated the 2018 ELN MRD recommendations based on significant developments in the field. New and revised recommendations were established during in-person and online meetings, and a 2-stage Delphi poll was conducted to optimize consensus. All recommendations are graded by levels of evidence and agreement. Major changes include technical specifications for next-generation sequencing-based MRD testing and integrative assessments of MRD irrespective of technology. Other topics include use of MRD as a prognostic and surrogate end point for drug testing; selection of the technique, material, and appropriate time points for MRD assessment; and clinical implications of MRD assessment. In addition to technical recommendations for flow- and molecular-MRD analysis, we provide MRD thresholds and define MRD response, and detail how MRD results should be reported and combined if several techniques are used. MRD assessment in AML is complex and clinically relevant, and standardized approaches to application, interpretation, technical conduct, and reporting are of critical importance.

Validation of thrombotic risk factors in 1381 patients with essential thrombocythaemia: A multicentre retrospective real-life study.

Thrombosis and haemorrhage are frequent in patients with essential thrombocythaemia (ET). The 2016 revised International Prognostic Score for Thrombosis in Essential Thrombocythaemia-thrombosis (r-IPSET-t) score stratifies patients into very-low- (VLR), low- (LR), intermediate- (IR) and high-risk (HR) groups. We validated the r-IPSET-t in the biggest population of patients with ET (n = 1381) to date and found it to be a better fit than the earlier IPSET-t score. With an average follow-up of 87.7 months, there were 0.578 thrombotic events/person-year and 0.286 bleeding events/person-year after diagnosis. The 10-year thrombosis-free survival was 88% and 99% for the r-IPSET-t LR and VLR groups (p < 0.001). Cytoreduction was a thrombotic risk factor in younger patients (aged <60 years, hazard ratio 9.49, p = 0.026; aged ≥60 years, hazard ratio 1.04, p = 0.93). In multivariable Cox regression analysis, anti-aggregation after diagnosis was protective for thrombosis (hazard ratio 0.31, p = 0.005) but a risk factor for major bleeding (hazard ratio 10.56, p = 0.021). Of the IPSET-t HR and LR groups, 132/780 and 249/301 were re-classified as LR and VLR respectively (p < 0.001). The European LeukemiaNET (ELN) does not recommend aspirin for VLR patients but in this real-life analysis 83.1% of VLR patients received it. Our results validate the r-IPSET-t score as more predictive for thrombosis than the ELN-recommended IPSET-t and raise concerns about unnecessary cytoreductive and anti-aggregative therapy.

Epidermal barrier function in patients after allogeneic hematopoietic stem cell transplantation - a pilot study.

Introduction: The skin is the typically and predominantly affected organ in patients after allogeneic hematopoietic stem cell transplantation (alloHSCT). The supportive therapy in patients after alloHSCT includes especially ultraviolet protection and the use of emollients. Aim: Due to the lack of studies regarding epidermal barrier function in patients with alloHSCT, our aims were to monitor dermatologically patients 1 year after the procedure with special emphasis on epidermal barrier function and to evaluate the properties of epidermal barrier function in patients with confirmed chronic GvHD (cGvHD). Material and methods: Our pilot study included 30 patients after alloHSCT and 20 healthy controls. In the group of patients after alloHSCT there were 10 individuals who were monitored dermatologically (including evaluation of skin, mucosae, nails and hair) within 1 year after the procedure (subgroup 1) and 20 patients with previously confirmed cGvHD (subgroup 2). We evaluated transepidermal water loss (TEWL), skin hydration and skin color. The clinical assessment and all noninvasive evaluations in patients included in subgroup 1 were performed before (at baseline) and 3, 6, 9 and 12 months after the procedure, while in subgroup 2 they were performed once. Results: In subgroup 1 we did not observe significant differences between baseline results and periods of assessments in TEWL values or corneometry, erythema and melanin measurements. In subgroup 2 the highest TEWL values and the lowest corneometry results were observed in patients with sclerodermoid chronic cutaneous GvHD in comparison to patients with lichenoid chronic cutaneous GvHD and patients with cGvHD but without skin lesions. TEWL values and melanin level were significantly higher in patients with cGvHD than in controls. Conclusions: Our pioneer observations proved the disturbed epidermal barrier function among patients after alloHSCT. Therefore it seems that proper skin care, including photoprotection, should be recognized as a crucial component in long-term management of these patients.

The diagnostic and prognostic significance of flow cytometric bone marrow assessment in myelodysplastic syndromes according to the European LeukemiaNet recommendations in single-centre real-life experience.

INTRODUCTION: This analysis attempts to determine the diagnostic and prognostic value of bone marrow (BM) evaluation by multiparameter flow cytometry in patients with myelodysplastic syndrome (MDS). MATERIALS AND METHODS: The study group consisted of patients who underwent diagnostic process in the years 2008-2017 due to cytopenia and finally were diagnosed with MDS (n = 71). The comparative group included patients with cytopenia diagnosed in the same period, whose definitive diagnosis was other than MDS (n = 39). Flow cytometric evaluation of BM was performed following the recommendations of the European LeukemiaNet (ELN) in all patients. RESULTS: The median number of immunophenotypic abnormalities found on granulocytes in the MDS group was significantly higher compared to the comparative group [2 (range 0-5) vs 0 (range 0-2); P < .0001]. Similarly, the median Ogata score was significantly higher in the MDS group [2 (range 0-4) vs 1 (range 0-3); P < .0001]. Since the disturbances of the CD11b/HLA-DR and CD11b/CD13 on granulocytes were significantly more common in MDS patients, the Ogata score was extended by these abnormalities, what resulted in its higher diagnostic sensitivity (82%) while preserving high specificity (87%). The positive correlation was found between risk score determined by the Revised International Prognostic Scoring System and the number of the BM immunophenotypic abnormalities (P = .017). CONCLUSIONS: Our results indicate that the diagnostic usefulness of the Ogata score may be increased by including the abnormal expression of CD11b/HLA-DR and CD11b/CD13 on granulocytes. Moreover, our findings suggest the prognostic significance of the number of BM cytometric abnormalities in MDS.

High efficacy of BGD (bendamustine, gemcitabine, and dexamethasone) in relapsed/refractory Hodgkin Lymphoma.

The optimal salvage therapy in relapsed/refractory Hodgkin lymphoma (R/R HL) has not been defined so far. The goal of this multicenter retrospective study was to evaluate efficacy and safety of BGD (bendamustine, gemcitabine, dexamethasone) as a second or subsequent line of therapy in classical R/R HL. We have evaluated 92 consecutive R/R HL patients treated with BGD. Median age was 34.5 (19-82) years. Fifty-eight patients (63%) had received 2 or more lines of chemotherapy, 32 patients (34.8%) radiotherapy, and 21 patients (22.8%) an autologous hematopoietic stem cell transplantation (autoHCT). Forty-four patients (47.8%) were resistant to first line of chemotherapy. BGD therapy consisted of bendamustine 90 mg/m2 on days 1 and 2, gemcitabine 800 mg/m2 on days 1 and 4, dexamethasone 40 mg on days 1-4. Median number of BGD cycles was 4 (2-7). The following adverse events ≥ 3 grade were noted: neutropenia (22.8%), thrombocytopenia (20.7%), anemia (15.2%), infections (10.9%), AST/ALT increase (2.2%), and skin rush (1.1%). After BGD therapy, 51 (55.4%) patients achieved complete remission, 23 (25%)-partial response, 7 (7.6%)-stable disease, and 11 (12%) patients experienced progression disease. AutoHCT was conducted in 42 (45.7%) patients after BGD therapy, and allogeneic HCT (alloHCT) in 16 (17.4%) patients. Median progression-free survival was 21 months. BGD is a highly effective, well-tolerated salvage regimen for patients with R/R HL, providing an excellent bridge to auto- or alloHCT.

Azacitidine for relapse of acute myeloid leukemia or myelodysplastic syndrome after allogeneic hematopoietic stem cell transplantation, multicenter PALG analysis.

OBJECTIVES: Relapse of myelodysplastic syndromes (MDS) or acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) belongs to the major causes of treatment failure. METHODS: Retrospective multicenter analysis of patients diagnosed with AML or MDS who had hematological relapse after allo-HSCT and were treated with azacitidine for this indication. RESULTS: Twenty-three patients receiving azacitidine as the first treatment of relapse (Group_1) and 8 patients receiving azacitidine after other treatment of relapse (Group_2) were included. There were 68% males, median age at initiation of azacitidine was 53 years (15-66). Median time to relapse was 3.5 months and 6.3 months in Group_1 and Group_2, respectively; median time from relapse to azacitidine 0.2 and 2.3 months. Azacitidine 75 mg/m2 , days 1-7, was administered in 78% and 75% of patients in Group_1 and Group_2, concomitant DLI in 48% and 50%. With median follow-up of 4.7 and 13.6 months, the median overall survival was 5.9 and 9.5 months. 17% and 37.5% patients proceeded to salvage allo-HSCT, with median OS of 11.6 months and not reached respectively. CONCLUSIONS: Azacitidine treatment for hematological relapse is associated with poor outcome; nevertheless, a proportion of patients may benefit from it, including patients receiving subsequent salvage allo-HSCT.

The risk of thrombosis in essential thrombocythemia is associated with the type of CALR mutation: A multicentre collaborative study.

OBJECTIVES: In patients with essential thrombocythemia (ET), after the JAK2V617F driver mutation, mutations in CALR are common (classified as type 1, 52-bp deletion or type 2, 5-bp insertion). CALR mutations have generally been associated with a lower risk of thrombosis. This study aimed to confirm the impact of CALR mutation type on thrombotic risk. METHODS: We retrospectively investigated 983 ET patients diagnosed in Spanish and Polish hospitals. RESULTS: With 7.5 years of median follow-up from diagnosis, 155 patients (15.8%) had one or more thrombotic event. The 5-year thrombosis-free survival (TFS) rate was 83.8%, 91.6% and 93.9% for the JAK2V617F, CALR-type 1 and CALR-type 2 groups, respectively (P = .002). Comparing CALR-type 1 and CALR-type 2 groups, TFS for venous thrombosis was lower in CALR-type 1 (P = .046), with no difference in TFS for arterial thrombosis observed. The cumulative incidence of thrombosis was significantly different comparing JAK2V617F vs CALR-type 2 groups but not JAK2V617F vs CALR-type 1 groups. Moreover, CALR-type 2 mutation was a statistically significant protective factor for thrombosis with respect to JAK2V617F in multivariate logistic regression (OR: 0.45, P = .04) adjusted by age. CONCLUSIONS: Our results suggest that CALR mutation type has prognostic value for the stratification of thrombotic risk in ET patients.

Primary cutaneous indolent B-cell lymphomas - a retrospective multicenter analysis and a review of literature.

Introduction: Primary cutaneous indolent B-cell lymphomas (PCBCLs) are not well characterized due to their rarity and indolent character.Methods: We retrospectively reviewed the data from 52 patients with primary cutaneous follicular lymphoma (PCFL) (n = 26), marginal zone lymphoma (PCMZL) (n = 25) or undefined PCBCL (n = 1) treated in 10 hematology centers in 1999-2019.Results: Patients characteristics and diagnostic approach: In almost half of the patients, pruritus or pain were present at diagnosis. The lesions were predominantly located on the head and trunk. The disease was present in a form of solitary infiltration or disseminated lesions with a similar frequency.Treatment details and outcomes: Surgery, radiotherapy, rituximab alone or combined with chemotherapy were applied as first-line treatment in 33%, 25%, 21% and 21% of patients, with complete response (CR) achieved by 94%, 83%, 50% and 70% of patients, respectively (p = 0.28). The median duration of response (DoR) was 65 months (95%CI 35-155).Survival: After the median follow-up time of 46 months (range: 3-225), the estimated 5-year overall survival (OS) and progression-free survival (PFS) were 93% and 54%, respectively.Discussion: Clinical presentation was largely consistent with the literature data, however, we observed some differences, including higher predilection to affect upper extremities (25%) and more frequent multifocal appearance in PCFCL (64%) and unifocal in PCMZL (70%).A high proportion of patients with indolent PCBCL achieved CR after the first-line therapy (77%), regardless of treatment mode. We did not find any impact of clinical features on treatment outcomes.Conclusions: All treatment modalities resulted in a high overall response rate. Surgery and/or radiotherapy are the optimal therapeutic options for patients with localized disease. The decision to treat systemically should rather be limited to the generalized form of the disease. High response rate, long duration of remission and excellent long-term survival confirm the truly indolent character of PCFCL and PCMZL.

Co-occurrence of unclassified myeloproliferative neoplasm and giant cell arteritis in a patient treated with allogeneic hematopoietic stem cell transplantation: a case report and literature review.

Myeloproliferative neoplasms (MPNs) are a group of hematologic disorders characterized by clonal proliferation of myeloid lineage cells. The diagnostic criteria are based on morphological features of bone marrow and peripheral blood cells but also include specific genomic mutations. In some patients, co-occurrence of hematologic and rheumatic diseases could be observed. To date, most of the reported cases concerned patients with myelodysplastic syndrome (MDS) or essential thrombocythemia (ET). In this paper, we present a case of a patient with a complicated diagnostic process leading to the diagnosis of unclassified MPN and giant cell arteritis (GCA). Routine tests did not reveal any mutations typical for MPNs such as JAK-2, CALR, MPL or BCR-ABL. Targeted next-generation sequencing (NGS) helped to confirm the diagnosis by demonstrating the presence of heterozygous ASXL1, TET2, SRSF2, and CBL mutations. The second important issue was the overlapping of symptoms of MPN and seronegative rheumatic disease, which finally was diagnosed as GCA. Leukocytosis and musculoskeletal pain, which were present at the time of diagnosis, resolved after allogeneic hematopoietic stem cell transplantation but recurred after a few months along with decreasing donor cell chimerism. Differentiation of the causes of recurrence of the symptoms was an important issue. This case shows the diagnostic challenge posed by co-incidence of MPN and rheumatic disease, especially its atypical variants.

Higher efficacy of intermediate dose cytarabine + G-CSF compared to cyclophosphamide + G-CSF in hematopoietic stem cell mobilization in patients with multiple myeloma.

BACKGROUND: There are several regimens used in hematopoietic stem cell (HSC) mobilization in multiple myeloma (MM). Cyclophosphamide (Cy) is one of the most commonly used agents, although it does not always result in collecting adequate number of CD34+ cells. Recently, cytarabine (Ara-C) has been proposed as potentially efficient and safe option. AIMS: Since the data regarding Ara-C in HSC mobilization is limited, the aim of our study was to compare retrospectively the efficiency and toxicity of G-CSF combined with either Ara-C or Cy in MM patients. MATERIALS & METHODS: Of a total of 89 patients, 43 received low or intermediate doses of Cy, and 46 were treated with 800 mg/m2 /day of Ara-C administered for two days. RESULTS: The mean peak of CD34+ cells/ul in peripheral blood was 132 (range, 84-202) in Ara-C and 51 (range, 29-69) in Cy cohort (p < 0.001). The median number of collected CD34+ cells (×106/kg) was 10.3 (range, 4.2-17.9) vs 4.5 (range, 2.7-8.9), respectively (p < 0.001). Mobilization failure was observed in one patient in Ara-C cohort (2%) and in 8 patients treated with Cy (19%) (p = 0.013). In the Ara-C group 98% of patients obtained more than 4×106 CD34+ cells/kg required for tandem transplantation. Moreover, we observed a trend toward increased paraprotein levels measured at transplant compared to before HSC mobilization in Ara-C cohort and significantly higher transfusion rates in that group. CONCLUSION: Our findings confirm higher HSC mobilization efficacy of Ara-C compared to Cy in MM patients. However, lower transfusions rate and better disease control of Cy may justify its use in some cases.

The Role of Measurable Residual Disease (MRD) in Hematopoietic Stem Cell Transplantation for Hematological Malignancies Focusing on Acute Leukemia.

The significance of measurable residual disease (MRD) in hematopoietic stem cell transplantation (HSCT) is well recognized in different hematological malignancies, but the evidence indicate that pre-transplant MRD status is of particular importance in acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). In ALL, inadequate response at the level of MRD is a commonly accepted risk factor for relapse and thus an indication for allogeneic HSCT. Similarly, growing evidence from the literature strongly suggest that MRD detected by multiparameter flow cytometry or molecular techniques should be also used for risk stratification in AML at the time of HSCT. Despite the well-defined association of MRD and outcomes of HSCT in acute leukemias, there are still many open issues such as the role of additional pre-transplant consolidation for MRD eradication, the ability of HSCT to overcome negative influence of MRD positivity on survival, the impact of conditioning regimen intensity on MRD clearance post HSCT, and transplantation outcomes or the selection of optimal donor with regards to MRD status. In addition, the role of MRD assessment in guiding post-transplant maintenance treatment should also be addressed in prospective trials. These open issues mostly awaiting further clinical studies will be discussed in our current review.

Autologous hematopoietic stem cell transplant for progressive diffuse systemic sclerosis: procedural success and clinical outcome in 5-year follow-up.

Systemic sclerosis is an autoimmune connective tissue disease affecting both skin and internal organs. Progressive disease with multiple organ involvement is considered to have a poor prognosis. Treatment possibilities are limited, but certain patients may benefit from autologous hematopoietic stem cell transplantation (auto-HSCT). We report a case of a 30-year-old woman with progressive diffuse systemic sclerosis treated with parenteral cyclophosphamide with unsatisfactory results. Due to progression of the disease and lack of alternative therapies auto-HSCT was performed. After instituting treatment with autologous hematopoietic stem cell transplantation no immunosuppressive therapy has been required during 5-year follow-up. Improvement in exertion tolerance, partial regression of skin lesions and stabilization of pulmonary and cardiovascular changes were observed. Currently therapeutic options in patients with progressive systemic sclerosis are limited. Hematopoietic stem cell transplantation might become an alternative therapeutic solution not only in the early phase of the disease but also among selected patients with progressive systemic sclerosis resistant to standard therapy.

Cyclophosphamide versus etoposide in combination with total body irradiation as conditioning regimen for adult patients with Ph-negative acute lymphoblastic leukemia undergoing allogeneic stem cell transplant: On behalf of the ALWP of the European Society for Blood and Marrow Transplantation.

Allogeneic hematopoietic cell transplantation (alloHCT) with myeloablative conditioning based on total body irradiation (TBI) is widely used for the treatment of adults with acute lymphoblastic leukemia (ALL). TBI is most frequently administered in combination with either cyclophosphamide (Cy/TBI) or etoposide (Vp/TBI). The goal of this study was to retrospectively compare these two regimens. Adult patients with Ph-negative ALL treated with alloHCT in first or second complete remission who received Cy/TBI (n = 1346) or Vp/TBI (n = 152) conditioning were included in the analysis. In a univariate analysis, as compared to Cy/TBI, the use of Vp/TBI was associated with reduced incidence of relapse (17% vs. 30% at 5 years, P = .007), increased rate of leukemia-free survival (60% vs. 50%, P = .04), and improved "graft versus host disease (GVHD) and relapse-free survival" (GRFS, 43% vs. 33%, P = .04). No significant effect could be observed in terms of the incidence of nonrelapse mortality or acute or chronic GVHD. In a multivariate model, the use of Vp/TBI was associated with reduced risk of relapse (HR = 0.62, P = .04) while the effect on other study end-points was not significant. In conclusion, conditioning regimen based on Vp combined with TBI appears more effective for disease control than the combination of Cy with TBI for adult patients with Ph-negative ALL treated with alloHCT.

BCRP mRNA and FLT3-ITD are independent poor risk factors in adult patients with acute myeloid leukemia and intermediate or normal karyotype.

PURPOSE: FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) is aberration associated with poor prognosis in AML. We have analyzed the expression of MDR-1, MRP-1, and BCRP mRNA in relation to FLT3-ITD in 100 AML adult patients with normal and intermediate karyotype. METHODS: The RQ-PCR method was performed to assess the expression of MDR-1, MRP-1, and BCRP mRNA, and the results were presented as coefficients calculated using an intermediate method according to Pfaffl's rule. RESULTS: According to univariate analysis, the following pretreatment variables negatively influenced disease-free survival (DFS): WBC count ≥25×109 /L (P=.037), MRP-1 mRNA ≥1.6818 (P=.028), BCRP mRNA ≥1.1892 (P=.004), FLT3-ITD (P=.005) and overall survival (OS): WBC count ≥25×109 /L (P=.031), MRP-1 mRNA ≥1.6818 (P=.01), BCRP mRNA ≥1.1892 (P=.01), FLT3-ITD (P=.001). When all prognostic variables were pooled into a multivariate model, we found that WBC count ≥25×109 /L (P=.026) and BCRP mRNA ≥1.1892 (P=.011). We observed trend in negative influence of FLT3-ITD on DFS (P=.057). BCRP mRNA ≥1.1892 (P=.035) and FLT3-ITD (P=.006) negatively, independently influenced the OS. CONCLUSIONS: The high expressions of BCRP mRNA calculated with Pfaffl's rule and FLT3-ITD are independent poor risk factors in adult patients with AML and intermediate or normal karyotype.

Use of tyrosine kinase inhibitors to prevent relapse after allogeneic hematopoietic stem cell transplantation for patients with Philadelphia chromosome-positive acute lymphoblastic leukemia: A position statement of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation.

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a standard of care for patients with Philadelphia chromosome (Ph)-positive acute lymphoblastic leukemia (ALL). The introduction of tyrosine kinase inhibitors (TKIs) to first-line therapy has improved overall outcomes; however, a significant proportion of patients still relapse after alloHSCT. Posttransplant TKI maintenance was demonstrated to reduce the risk of relapse in a large retrospective study and, therefore, should be considered a valuable option. This consensus paper, written on behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation, presents an overview of clinical studies on the use of TKIs after alloHSCT and proposes practical recommendations regarding the choice of TKI, treatment timing, and dosage. It is hoped that these recommendations will become the state of art in this field and, more importantly, lead to a reduction of Ph-positive ALL relapse after alloHSCT. Cancer 2016;122:2941-2951. © 2016 American Cancer Society.

Mild chronic graft-versus-host disease may alleviate poor prognosis associated with FLT3 internal tandem duplication for adult acute myeloid leukemia following allogeneic stem cell transplantation with myeloablative conditioning in first complete remission: a retrospective study.

Internal tandem duplication (ITD) of the FLT3 gene (Fms-like tyrosine kinase 3) is the most commonly found mutation in acute myeloid leukemia (AML). The significance of FLT3-ITD at diagnosis was retrospectively estimated for allo-HSCT (allogeneic hematopoietic stem cell transplantation) outcomes in 140 patients, median age of 38, undergoing allo-HSCT after myeloablative conditioning in first complete remission of AML. FLT3-ITD was detected at AML diagnosis in 42/140 (30%) of included into this study patients. At 3 years, relapse incidence (RI) following allo-HSCT in AML patients with intermediate or normal karyotype was significantly higher in those FLT3-ITD positive than FLT3-ITD negative [52.9 vs. 20.4%, P = 0.002]. Additionally, patients with mild chronic graft-versus-host disease (cGvHD) had significantly lower RI compared to patients with moderate or severe grade cGvHD or those not experiencing cGvHD, respectively, 4.8 vs. 36.0 vs. 27.8%, P = 0.032. FLT3-ITD was harboring a poor prognosis in AML with intermediate or normal karyotype and significantly increased risk of relapse following allo-HSCT. It appears that allo-HSCT does not cure patients with FLT3-ITD, unless they develop symptoms of mild cGvHD and graft versus leukemia, which may decrease RI.

Role of Donor Activating KIR-HLA Ligand-Mediated NK Cell Education Status in Control of Malignancy in Hematopoietic Cell Transplant Recipients.

Some cancers treated with allogeneic hematopoietic stem cell transplantation (HSCT) are sensitive to natural killer cell (NK) reactivity. NK function depends on activating and inhibitory receptors and is modified by NK education/licensing effect and mediated by coexpression of inhibitory killer-cell immunoglobulin-like receptor (KIR) and its corresponding HLA I ligand. We assessed activating KIR (aKIR)-based HLA I-dependent education capacity in donor NKs in 285 patients with hematological malignancies after HSCT from unrelated donors. We found significantly adverse progression-free survival (PFS) and time to progression (TTP) in patients who received transplant from donors with NKs educated by C1:KIR2DS2/3, C2:KIR2DS1, or Bw4:KIR3DS1 pairs (for PFS: hazard ratio [HR], 1.70; P = .0020, Pcorr = .0039; HR, 1.54; P = .020, Pcorr = .039; HR, 1.51; P = .020, Pcorr = .040; and for TTP: HR, 1.82; P = .049, Pcorr = .096; HR, 1.72; P = .096, Pcorr = .18; and HR, 1.65; P = .11, Pcorr = .20, respectively). Reduced PFS and TTP were significantly dependent on the number of aKIR-based education systems in donors (HR, 1.36; P = .00031, Pcorr = .00062; and HR, 1.43; P = .019, Pcorr = .038). Furthermore, the PFS and TTP were strongly adverse in patients with missing HLA ligand cognate with educating aKIR-HLA pair in donor (HR, 3.25; P = .00022, Pcorr = .00045; and HR, 3.82; P = .027, Pcorr = .054). Together, these data suggest important qualitative and quantitative role of donor NK education via aKIR-cognate HLA ligand pairs in the outcome of HSCT. Avoiding the selection of transplant donors with high numbers of aKIR-HLA-based education systems, especially for recipients with missing cognate ligand, is advisable.