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Patients with essential thrombocythaemia (ET) have an increased risk of thromboembolic events, which may differ according to different cytoreductive drugs. We investigated the effect of cytoreductive treatment on platelet function and turnover in ET patients. Blood samples were obtained at 1 and 24 h after aspirin intake. Platelet function was evaluated by platelet aggregation and flow cytometry. Platelet turnover was assessed by immature platelet count, immature platelet fraction (IPF) and mean platelet volume (MPV). A total of 47 ET patients were included and grouped into 21 patients not receiving cytoreductive treatment, 15 patients receiving hydroxycarbamide and 11 patients receiving pegylated interferon alpha (peg-IFN). Patients receiving peg-IFN had significantly higher IPF and MPV than the other ET groups. Patients not receiving cytoreductive treatment had significantly higher platelet aggregation 24 h after aspirin intake than the other ET groups (p-values from 0.03 to 0.0002). Patients receiving hydroxycarbamide had significantly higher expression of platelet granule makers, P-selectin and CD63, than patients receiving peg-IFN (p-values ≤0.003). Cytoreduction provides more consistent platelet inhibition compared with no cytoreductive treatment. Moreover, peg-IFN provides superior inhibition of platelet activation markers than hydroxycarbamide, which in part may explain differences in risk of thromboembolic events in ET patients.

Longitudinal molecular measurable residual disease (MRD) sampling after completion of therapy serves as a refined tool for identification of imminent relapse of acute myeloid leukaemia (AML) among patients in long-term haematological complete remission. Tracking of increasing quantitative polymerase chain reaction MRD before cytomorphological reappearance of blasts may instigate individual management decisions and has paved the way for development of pre-emptive treatment strategies to substantially delay or perhaps even revert leukaemic regrowth. Traditionally, MRD monitoring is performed using repeated bone marrow aspirations, albeit the current European LeukemiaNet MRD recommendations acknowledge the use of peripheral blood as an alternative source for MRD assessment. Persistent MRD positivity in the bone marrow despite continuous morphological remission is frequent in both core binding factor leukaemias and nucleophosmin 1-mutated AML. In contrast, monthly assessment of MRD in peripheral blood superiorly separates patients with imminent haematological relapse from long-term remitters and may allow pre-emptive therapy of AML relapse.

Technological advances have made it possible to offer home-based chemotherapy to patients without health care professionals being present. Prior studies on effects of home-based treatment lack inclusion of patients with hematologic malignancies. We present data from a multicenter single-arm feasibility and safety study of home-based intensive chemotherapy in patients with newly diagnosed acute myeloid leukemia and their quality of life and psychological wellbeing. This national study included patients from six sites in Denmark who received intensive chemotherapy on programmed CADD Solis infusion pumps through a central venous catheter and were also managed as outpatients during treatment-induced pancytopenia. Data are presented from 104 patients, receiving 272 treatments with 1.096 (mean 4.57, SD 3.0) home infusion days out of 1.644 treatment days (67 %). Sixty-two of 168 (36.9 %) reinduction and consolidation treatment cycles ensuing pancytopenia phases were solely handled in the outpatient clinic. Patients reported high satisfaction with home-based treatment, which had a positive influence on their ability to be involved in their treatment and be socially and physically active. No unexpected events occurred during the intervention. Overall, patients improved in all quality of life outcomes over time. Home-based intensive chemotherapy treatment was feasible and safe in this population. ClinicalTrials.gov identifier: NCT04904211

This open-label, randomized, phase 3 trial (NCT02577406) compared enasidenib, an oral IDH2 inhibitor, with conventional care regimens (CCR) in patients aged =60 years with late-stage, mutant-IDH2 acute myeloid leukemia (AML) relapsed/refractory (R/R) to 2 or 3 prior AML-directed therapies. Patients were first preselected to a CCR (azacitidine, intermediate-dose cytarabine, low-dose cytarabine, or supportive care), and then randomized (1:1) to enasidenib 100 mg/day or CCR. The primary endpoint was overall survival (OS). Secondary endpoints included event-free survival (EFS), time to treatment failure (TTF), overall response rate (ORR), hematologic improvement (HI), and transfusion independence (TI). Overall, 319 patients were randomized to enasidenib (n=158) or CCR (n=161). Median age was 71 years. Median (range) enasidenib exposure was 142 days (3-1270) and CCR was 36 days (1-1166). One enasidenib (0.6%) and 20 CCR (12%) patients received no randomized treatment, and 30% and 43%, respectively, received subsequent AML-directed therapies during follow-up. Median OS with enasidenib vs CCR was 6.5 vs 6.2 months (HR [hazard ratio] 0.86; P=.23); 1-year survival was 37.5% vs 26.1%. Enasidenib meaningfully improved EFS (median 4.9 months, vs 2.6 months with CCR; HR 0.68; P=.008), TTF (median 4.9 vs 1.9 months, HR 0.53; P

Background Patients with essential thrombocythemia (ET) and coronary artery disease (CAD) have increased risk of thromboembolic complications. In addition, a reduced antiplatelet effect of aspirin has been demonstrated in both patient groups. As ET is a platelet disorder, platelets may be more important for the thromboembolic risk in ET than in CAD. We aimed to investigate the antiplatelet effect of aspirin and platelet turnover in ET versus CAD patients. Methods We included 48 ET patients and an age-matched group of 48 CAD patients. The effect of aspirin was evaluated by thromboxane B2 (TXB2) levels and platelet aggregation. Platelet turnover was assessed by immature platelet count (IPC) and immature platelet fraction (IPF). Results ET patients had reduced effect of aspirin compared with CAD patients, demonstrated by significantly higher TXB2 levels (median of differences = 22.3 ng/mL, p Conclusion ET patients have lower 24-hour antiplatelet effect of aspirin than CAD patients. This may be explained by an increased platelet production and turnover counteracting the antiplatelet effect of aspirin. These findings strengthen the rationale for exploring novel antiplatelet regimens in ET patients to reduce the risk of cardiovascular events.

Bleeding and thrombosis are well-known complications to hematological malignancies, and changes in fibrinolysis impact both these issues. In the present systematic review, we provide an overview and discussion of the current literature in regards to clinical manifestations, diagnosis, and treatment of altered fibrinolysis in patients suffering from hematological malignancies, beyond acute promyelocytic leukemia. We performed a systematic literature search employing the databases Pubmed, Embase, and Web of Science to identify original studies investigating fibrinolysis in hematological malignancies. Studies investigating fibrinolysis in acute promyelocytic leukemia or disseminated intravascular coagulation were excluded. We identified 32 studies fulfilling the inclusion criteria. A majority of the studies were published more than two decades ago, and none of the studies examined all available markers of fibrinolysis or used dynamic clot lysis assays. In acute leukemia L-asparaginase treatment induced a hypofibrinolytic state, and prior to chemotherapy there seemed to be little to no change in fibrinolysis. In studies examining fibrinolysis during chemotherapy results were ambiguous. Two studies examining multiple myeloma indicated hypofibrinolysis prior to chemotherapy, and in another plasma cell disease, amyloid light chain-amyloidosis, clear signs of hyperfibrinolysis were demonstrated. In myeloproliferative neoplasms, the studies reported signs of hypofibrinolysis, in line with the increased risk of thrombosis in this disease. Only one study regarding lymphoma was identified, which indicated no alterations in fibrinolysis. In conclusion, this systematic review demonstrated that only sparse, and mainly old, evidence exists on fibrinolysis in hematological malignancy. However, the published studies showed a tendency toward hypofibrinolysis in myeloproliferative disorders, an increased risk of hyperfibrinolysis, and bleeding in patients with AL-amyloidosis, whereas studies regarding acute leukemias were inconclusive except with regard to L-asparaginase treatment, which induced a hypofibrinolytic state.

In the present study, we quantify the progress in overall survival (OS) during the period 2000-2016 among Danish patients with acute myeloid leukaemia (AML). This population-based study, including 3820 adult patients with AML, demonstrates a significantly improved OS over time with the 2-year age-standardised OS increasing from 22% in 2002 to 31% in 2016. The improvement in OS was exclusively seen in patients with AML aged ≥50 years, with absolute improvements in 2-year OS from 2002 to 2016 of ≥10% among patients aged 50-75 years and a small absolute increase in those aged >75 years.

Overexpressed genes may be useful for monitoring of measurable residual disease (MRD) in patients with childhood acute myeloid leukemia (AML) without a leukemia-specific target. The normal expression of five leukemia-associated genes (SPAG6, ST18, MSLN, PRAME, XAGE1A) was defined in children without hematologic disease (n = 53) and children with suspected infection (n = 90). Gene expression at AML diagnosis (n=50) and during follow-up (n = 21) was compared with child-specific reference values. At diagnosis, 34/50 children (68%) had high expression of at least one of the five genes, and so did 16/31 children (52%) without a leukemia-specific target. Gene expression was quantified in 110 peripheral blood (PB) samples (median, five samples/patient; range, 1 to 10) during follow-up in 21 patients with high expression at diagnosis. All nine patients with PB sampling performed within 100 days of disease recurrence displayed overexpression of SPAG6, ST18, PRAME, or XAGE1A at a median of 2 months (range, 0.6 to 9.6 months) before hematologic relapse, whereas MSLN did not reach expression above normal prior to hematologic relapse. Only 1 of 130 (0.8%) follow-up analyses performed in 10 patients in continuous complete remission had transient expression above normal. SPAG6, ST18, PRAME, and XAGE1A expression in PB may predict relapse in childhood AML patients and facilitate MRD monitoring in most patients without a leukemia-specific target.

Essential thrombocythemia (ET) is a myeloproliferative neoplasm characterized by increased platelet counts. ET has an incidence of 0.6 to 2.5 per 100,000 per year in Europe and North America. The disease is characterized by an increased thromboembolic risk, possibly caused by increased platelet counts. Furthermore, increased platelet function and/or increased platelet turnover may play a role. We aimed to explore: (1) whether platelet function and platelet turnover are increased in ET patients compared with healthy controls, and (2) whether these parameters are associated with increased thromboembolic risk and, therefore, may support decision-making on treatment in ET patients. We performed a systematic literature search on March 20, 2020 in Embase and PubMed following the Preferred Reporting Items for Systematic and Meta-Analysis (PRISMA) guidelines. In total, 1,923 articles were identified, 38 of which were included according to prespecified inclusion and exclusion criteria. Among the 38 studies, platelet activation (CD36 and CD62P) was investigated in 18 studies and was found to be increased in 12 of these. Platelet aggregation was investigated in 21 studies and was reported to be reduced in 20 of them. Platelet turnover (immature platelet count and mean platelet volume) was investigated in five studies with inconclusive results. No parameters were reported to predict the risk of thromboembolic events. In conclusion, platelet activation was increased in ET patients, but platelet aggregation was reduced. Future studies exploring markers of thromboembolic risk in ET patients are warranted.

We report the use of extracorporeal membrane oxygenation (ECMO) in a 28-year-old woman who had an influenza infection complicated with severe acute respiratory distress syndrome (ARDS) during treatment for acute myeloid leukemia. Despite ventilator management with positive end-expiratory pressure, nitrogen oxide inhalation, and prone positioning, there was severe hypoxemia. ECMO led to improvement in gas exchange and lung mechanics. This case shows that ECMO can be lifesaving in the treatment of immunocompromised patients who have hypoxemia that is refractory to conventional treatment.

Relapse remains the most common cause of treatment failure for patients with acute myeloid leukemia (AML) who undergo allogeneic stem cell transplantation (alloSCT), and carries a grave prognosis. Multiple studies have identified the presence of measurable residual disease (MRD) assessed by flow cytometry before alloSCT as a strong predictor of relapse, but it is not clear how these findings apply to patients who test positive in molecular MRD assays, which have far greater sensitivity. We analyzed pretransplant blood and bone marrow samples by reverse-transcription polymerase chain reaction in 107 patients with NPM1-mutant AML enrolled in the UK National Cancer Research Institute AML17 study. After a median follow-up of 4.9 years, patients with negative, low (

Myeloid and lymphoid malignancies are postulated to have distinct pathogenic mechanisms. The recent observation that patients with a myeloproliferative neoplasm have an increased risk of developing lymphoproliferative malignancies has challenged this assumption. We collected a nationwide cohort of patients with both malignancies. Patients diagnosed between 1990 and 2015 were identified through the national Danish Pathology Registry. We identified 599 patients with a myeloproliferative neoplasm and a concomitant or subsequent diagnosis of lymphoma. Histopathological review of the diagnostic samples from each patient led to a final cohort of 97 individuals with confirmed dual diagnoses of myeloproliferative neoplasm and lymphoma. The age range at diagnosis of these individuals was 19-94 years (median: 71 years). To avoid the inclusion of cases of therapy-induced myeloproliferative neoplasm occurring in patients previously treated for lymphoma, only patients with myeloproliferative neoplasm diagnosed unequivocally before the development of lymphoma were included. The average time interval between the diagnoses of the two malignancies was 1.5 years. In the majority of patients (90%) both diagnoses were established within 5 years of each other. Among the lymphoma entities, the frequency of peripheral T-cell lymphomas was markedly increased. Interestingly, all but one of the T-cell lymphomas were of angioimmunoblastic type. These findings suggest that a myeloproliferative neoplasm and lymphoproliferative malignancy developing in the same patient may have common pathogenic events, possibly already at the progenitor level. We believe that the molecular characterization of the newly developed biorepository will help to highlight the mechanisms driving the genesis and clonal evolution of these hematopoietic malignancies.

Close surveillance of measurable residual disease (MRD) following completion of therapy for acute myeloid leukemia (AML) enables early detection of relapse in time for pre-emptive treatment. Today this is available only for the fraction of patients with recurrent targets quantifiable with standardized RT-qPCR. Patient-tailored MRD monitoring based on leukemia-specific mutations may be an attractive option in patients lacking such aberrations. In this population-based study, we used whole exome sequencing (WES) to identify leukemia-specific mutations suitable for MRD monitoring, and targeted deep sequencing (deep seq) and droplet digital PCR (ddPCR) for quantitative monitoring in children with AML. We investigated the clinical applicability of patient-tailored deep seq and ddPCR for early detection of AML relapse in peripheral blood (PB). All children (0-18 years) with de novo AML diagnosed between March 2013 and December 2018 who achieved complete remission after treatment according to the NOPHO-DBH AML 2012 protocol (EudraCT number: 2012-002934-35) in Sweden, Denmark, the Netherlands, Norway and Finland were eligible for the study (n = 179). In the study, patients had PB samples drawn at monthly intervals and biobanked for retrospective analyses of leukemia-specific mutations. In patients with a marker for RT-qPCR, samples were also analyzed with RT-qPCR with results reported back to the clinic. Included patients (n = 134) had PB samples drawn starting one month after last consolidation course or date of allogeneic stem cell transplantation and until relapse or end of follow-up (12-18 months following therapy completion), (median 11 samples/patient, range 1-28). Out of the 34 patients who experienced relapse during the study period, sufficient biological material for WES at diagnosis was available from 26 patients (21 hematologic and 5 molecular relapses as determined by RT-qPCR in patients with a suitable marker). For these 26 patients, the median time from end of therapy to relapse (hematologic or molecular) was 6.7 months (range 3.1-23.7). In 24/26 patients, leukemia-specific mutations could be identified at diagnosis. For 22/24 patients, leukemia-specific mutations were verified to be present at relapse (hematologic or molecular) either by WES or deep seq. In the remaining two patients with molecular relapse, leukemia-specific mutations were not verified at molecular relapse. In the 22 patients where leukemia-specific mutations could be detected, 55 mutations (median 3/patient, range 1-4) were quantified with deep seq (limit of detection [LoD] 0.02% variant allele frequency [VAF]) in 111 PB samples (263 analyses) with a sampling interval of 0.9 months (range 0.2-2.6). Parallel ddPCR analyses of 43 mutations from 20 of these patients were performed in 100 PB samples (206 analyses) with a median LoD of 0.04% VAF (range 0.003-0.1%). Deep seq and ddPCR were concordant in 187/206 (91%) of analyses and 84/100 (84%) of analyzed samples. Median VAF in the 113 paired analyses with MRD level above LoD was 0.34% (range 0.02-47.23) with deep seq and 0.38% (range 0.02-45.97) with ddPCR (P = 0.7). Obtained VAFs correlated strongly between the two methods (Spearman's ρ 0.91, P < 0.0001). Nineteen of the analyzed patients experienced hematologic relapse and in 17 of these, at least one mutation was detected in blood before relapse. The median lead time from MRD positivity to hematologic relapse was 3.2 months (range 0.6-7.9) when analyzed with deep seq (n = 17) and 2.6 months (range 0.5-7.9) when analyzed with ddPCR (n = 15). Lead times in patients analyzed with both deep seq and ddPCR showed comparable Kaplan-Meier curves (Fig. 1A). Additional comparison of the lead times achieved with deep seq/ddPCR and RT-qPCR of WT1 expression (n = 6) and recurrent genetic aberrations (n = 5) showed similar Kaplan-Meier curves (Fig. 1B-C). As assessed by deep seq in patients who were not pre-emptively treated, relapse kinetics varied greatly between patients; median VAF doubling time was 12 days with a range of 4-43 (n = 17). In conclusion, highly sensitive quantification of leukemia-specific mutations in a patient-tailored manner using deep seq or ddPCR enables post-treatment monitoring for the majority of children with AML. Frequent assessment in blood may allow for timely identification of pending relapses to initiate pre-emptive treatment strategies. Figure 1 Figure 1. Disclosures Abrahamsson: wedish Children´s Cancer Foundation. Research grants and 50% senior research position for clinical research on pediatric leukemia: Research Funding.

We report a case presenting with recurrent episodes of severe hypothermia preceding the diagnosis of Hodgkin lymphoma. The episodes of hypothermia were accompanied by other symptoms of autonomic dysfunction, mainly hypotension, which could be caused by autonomic neuropathy as part of a paraneoplastic syndrome. In comparison with previous reports describing an association between the presence of hypothermia and an adverse outcome, the present patient has responded well to lymphoma-specific treatment and is currently in an ongoing complete remission. Due to the peculiar cyclic pattern of the hypothermic episodes presented in this case, we hypothesize whether intermittent release of disease-related chemo- and cytokines could be a plausible pathogenetic explanation.

Background: Relapse remains a serious event and main obstacle to permanent cure in childhood acute myeloid leukemia (AML). Reduction of measurable/minimal residual disease (MRD) assessed by real-time quantitative PCR (qPCR) during therapy is predictive of outcome in adults but persistent MRD positivity may be observed despite long-term remission and hamper accurate risk assignment. Sequential MRD determinations, rather than analysis at single landmark time points, may better capture the dynamics of leukemia eradication and identify relapse at molecular levels when applied in the post-therapy setting. We investigated the post-induction qPCR MRD kinetics in peripheral blood (PB) and bone marrow (BM) in a large cohort of childhood AML patients and demonstrate the utility of serial assessments for disease surveillance after therapy completion. Methods: We collected the results from qPCR MRD analyses of 774 samples (BM 347, PB 427) from 75 children with AML harboring recurrent fusion transcripts (32 RUNX1-RUNX1T1, 24 CBFB-MYH11, 16 KMT2A-MLLT3 and 3 KMT2A-ELL). Patients were treated according to The Nordic Society for Paediatric Haematology and Oncology (NOPHO)-AML 2004 or NOPHO-DBH AML 2012 protocols (2004 - 2016), or AML-BFM 2012 protocol (2014 - 2016). Only patients who achieved complete remission (CR) during induction therapy and received standard-risk consolidation without allografting were eligible for the study. Risk of relapse as a function of time of MRD positivity in sequential samples from BM or PB during consolidation therapy was modeled using restricted cubic splines. Considering shifting from MRD negative to positive in PB and MRD increments in BM above 5x10-4 as time-dependent variables, the Mantel-Byar method was applied to evaluate the prognostic impact of MRD kinetics during follow-up. Results: Risk of relapse was independent of MRD persistence in BM during therapy, but showed a strong correlation with time of MRD positivity in PB where 8/8 patients with detectable MRD after first consolidation course relapsed (Figure 1A and 1B). At therapy completion, MRD level in BM did not correlate to outcome, HR=0.64/MRD log reduction, 95% confidence interval (CI):0.32 - 1.26 (P=0.19), and there was no difference in 3-year cumulative incidence of relapse (CIR) according to MRD status (P=0.51, Figure 2A). Four patients remained MRD positive throughout consolidation therapy and all subsequently relapsed, whereas 7/28 patients who were MRD negative in PB at the end of therapy suffered relapse, 3-year CIR=27%, CI:14% - 49% (P Shifting from negative to positive in PB during follow-up predicted subsequent relapse in 10/10 patients. All 253 PB samples collected during follow-up from 36 patients in continuous CR were MRD negative. In core binding factor (CBF) AML, persistent low-level MRD positivity in BM was frequent (detected in 38% of patients tested within six months of therapy completion) but an increment to above 5x10-4 heralded subsequent relapse in 12/12 patients. Pre-relapse MRD kinetics were delineated in 16 patients and revealed a median log increment/30 days of 0.8 (range:0.4 - 1.5) in CBF patients versus 2.2 (range:1.1 - 3.7) in patients with KMT2A-MLLT3 (P=0.008). Perspectives: This study demonstrates that qPCR MRD monitoring in PB, rather than BM, represents an accurate discriminator of prognosis and is a highly informative tool for disease surveillance in childhood AML. Early relapse detection during follow-up may facilitate preemptive therapy strategies of molecular relapse, possibly improving relapse treatment outcomes. Disclosures No relevant conflicts of interest to declare.

Treatment of acute myeloid leukemia (AML) remains a high-risk venture for the patient suffering from the disease. There is a real risk of succumbing to the treatment rather than the disease, and even so, cure is much less than certain. Since the establishment of complete remission as a prerequisite for cure in the 1960s, a number of years passed before advanced techniques for detecting minute amounts of disease matured sufficiently for clinical implementation. The two main techniques for detection of measurable residual disease (MRD) remain qPCR and multicolor flow cytometry. When performed in expert laboratories, both these modalities offer treating physicians excellent opportunity to follow the amount of residual disease upon treatment and offer unparalleled prognostication. In some AML and age group subsets, evidence now exist to support the choice of both proceeding to allogeneic transplant and not doing so. In other AML subgroups, MRD has sufficient discriminative power to identify patients likely to benefit from allogeneic transplant and patients likely not to. After treatment or transplantation, follow-up by molecular techniques can, with high certainty, predict relapse months before bone marrow function deterioration. On the other hand, options upon so-called molecular relapse are less well tested but recent evidence supports the use of azacitidine both in transplanted patients and patients consolidated with chemotherapy. In conclusion, MRD testing during treatment is a superb prognosticator and a major tool when choosing whether a patient should be transplanted or not. The exact use of MRD testing after treatment is less well defined but evidence is mounting for the instigation of treatment upon rising MRD levels (pre-emptive treatment) before morphologically detectable relapse.

Background: Even though children with acute myeloid leukemia (AML) receive a very intensive chemotherapy and most achieve a complete remission (CR) ~30% of patients suffer from relapse. Post-treatment monitoring of measurable residual disease (MRD) can allow detection of a re-emerging leukemic clone several months before clinical relapse, and studies are in progress that aim at treating children with a molecular relapse. Specific genetic aberrations can be used for disease monitoring after therapy completion, but even though oncogenic fusion transcripts are more common in childhood than adult AML, NPM1 mutation is much rarer and consequently MRD measurements based on these aberrations are clinically applicable in only ~40% of childhood AML patients. Thus, a considerable fraction of patients do not have a suitable leukemia-specific molecular MRD target, but genes with an abnormally high expression in the leukemic cells might be candidate MRD targets in those patients. WT1 overexpression in childhood AML is well described, and if distinctly overexpressed at diagnosis, serves as a suitable MRD target in a large proportion of patients. Gene expression profiling has identified several other genes with an abnormally high expression in the leukemic blasts compared to normal hematopoietic cells. We investigated the applicability of 4 leukemia-associated genes (PRAME, GAGED2, ST18, SPAG6) as targets for early detection of relapse in peripheral blood (PB) in a Danish cohort of childhood AML patients, defined child-specific reference values of gene expression based on a large material of PB and BM samples from hematologically healthy children, and investigated gene expression levels under the presence of infection. Methods: We investigated the expression of 4 leukemia-associated genes (PRAME, GAGED2, ST18, SPAG6) in hematologically healthy children (n=53) and during suspected infection in febrile but otherwise healthy children (n=90). Gene expression in de novo AML at diagnosis (n=50) and during follow-up (n=20) was compared with child-specific reference values. We defined the 95th percentile of expression levels in hematologically healthy children as the upper limit of normal expression. RT-qPCR analyses were performed in compliance with EAC protocols and due to concordant qPCR efficiencies the ΔΔCq method for relative quantification could be applied. Results: At AML diagnosis, 64% had high expression of at least 1 of the 4 genes defined as >20-fold overexpression compared to hematologically healthy children. Nine out of 10 patients (90%) without established molecular MRD targets or high WT1 expression had high expression of at least 1 of the 4 genes. All 7 children with t(9;11) had GAGED2>1000-fold overexpressed. Gene expression was quantified in 99 PB samples (163 RT-qPCR analyses) during follow-up in 20 patients with distinct overexpression at diagnosis. All 10 patients with PB sampling performed within 100 days of disease recurrence displayed expression above normal by a median of 1.6 months (range 0.5-6 months) before hematological relapse. Patients with CBF-AML had a significantly longer interval between molecular relapse and hematological relapse than patients with non-CBF-AML (2.5 months (range 0.8-6 months) vs. 0.9 months (range 0.5-2 months), p=0.047). One patient with PB sampling performed only once at 119 days prior to hematological relapse did not show any molecular evidence of disease recurrence before hematological relapse. Only 1 of 96 (1%) post-therapy follow-up analyses performed in 9 patients in continuous CR for >5 years after diagnosis had expression above normal. In this case, a 9-year-old girl in continuous CR had an increase in ST18 expression, however the increase was transient and returned to normal level in the following samples. We found no clinically relevant influence of fever on gene expression levels, except for GAGED2, where 21% of febrile children had expression above normal. Conclusions: Sequential post-therapy monitoring of overexpressed genes in PB can predict relapse in childhood AML patients and facilitates molecular MRD monitoring in 90% of patients without a leukemia-specific target or WT1 overexpression. Frequent PB sampling (every 4-6 weeks) is necessary to detect an upcoming relapse, however in the post-treatment follow-up setting PB serves as an attractive and easily accessible source of preference compared to BM aspiration. Disclosures No relevant conflicts of interest to declare.

Correct action upon re-emergence of minimal residual disease in acute myeloid leukaemia (AML) patients has not yet been established. The applicability of demethylating agents and use of allogeneic stem cell transplantation will be dependent on pre-relapse AML growth rates. We here delineate molecular growth kinetics of AML harbouring MLL partial tandem duplication (MLL-PTD; 37 cases) compared to those harbouring MLL translocations (43 cases). The kinetics of MLL-PTD relapses was both significantly slower than those of MLL translocation positive ones (median doubling time: MLL-PTD: 24 d, MLL-translocations: 12 d, P = 0·015, Wilcoxon rank sum test), and displayed greater variation depending on additional mutations. Thus, MLL-PTD+ cases with additional RUNX1 mutations or FLT3-internal tandem duplication relapsed significantly faster than cases without one of those two mutations (Wilcoxon rank sum test, P = 0·042). As rapid relapses occurred in all MLL subgroups, frequent sampling are necessary to obtain acceptable relapse detection rates and times from molecular relapse to haematological relapse (blood sampling every second month: MLL-PTD: 75%/50 d; MLL translocations: 85%/25 d). In conclusion, in this cohort relapse kinetics is heavily dependent on AML subtype as well as additional genetic aberrations, with possibly great consequences for the rational choice of pre-emptive therapies.

Relapse remains a major therapeutic challenge in children with acute myeloid leukemia (AML). Outcome after relapse may improve if preemptive therapy is initiated at first evidence of leukemia regrowth. Early detection of imminent relapse requires molecular measurable residual disease (MRD) monitoring after therapy completion. Today, this is possible only in about 40% of children with AML that harbor genetic abnormalities applicable for quantification using standardized qPCR assays. To enable disease surveillance for all patients, we developed patient-tailored deep sequencing (DS) MRD analysis, which provides highly sensitive detection of leukemia-specific mutations. We investigated the potential of this method for early relapse detection in peripheral blood (PB), the only easily accessible source for MRD sampling in children. PB samples were collected at monthly intervals during follow-up from 45 children diagnosed with AML and treated according to The Nordic Society of Pediatric Haematology and Oncology (NOPHO)-DBH AML 2012 protocol between January 2013 and May 2016 in Denmark, Norway, Sweden and Finland (508 samples, median 11 samples/patient, range 3-27). Nine patients with relapse (median age 5 years, range 0-8) had available diagnostic and relapse material and were included in this study. The patients displayed core binding factor abnormalities (n=3), KMT2A-rearrangements (n=3), monosomy 7 (n=1) or normal karyotype (n=2) at AML diagnosis. Leukemia-specific single nucleotide variants (SNVs) were identified with exome sequencing (ES) of sorted leukemic cells with lymphocytes or remission PB as constitutive DNA template. A variant allele frequency (VAF) with 95% confidence interval including 50% indicates presence of the mutation in all leukemic cells at diagnosis. With the exception of 2 cases with only subclonal mutations at diagnosis, leukemia-specific SNVs with VAF of 50% at diagnosis and persistence at relapse were selected as MRD targets. MRD target mutations were quantified in PB samples preceding overt relapse using patient-tailored DS assays with sensitivity of VAF 0.02%. In diagnostic samples, ES identified 53 leukemia-specific SNVs (median 4 SNVs/patient, range 2-12) of which 33 were also present at relapse (median 2 SNVs/patient, range 1-9). The number of mutations identified at diagnosis increased with age (Rs 0.83, p=0.006). All patients had at least one leukemia-specific SNV detected at both diagnosis and relapse. Twenty-one MRD target mutations (median 2 SNVs/patient, range 1-3) were quantified in PB (55 samples, median sampling interval 28 days, range 11-80) using DS. In 8/9 patients, at least one SNV was detected in PB before overt relapse occurred. The first PB sample showing MRD positivity (median VAF 0.14%, range 0.03-0.44) preceded hematological relapse at a median interval of 3 months (range 0-7.9). In 6 patients not preemptively treated, the median doubling time based on VAF increments was 7 days, with great variability between individuals and genotypes (range 4-28 days). Three patients had molecular relapse diagnosed by qPCR used in clinical diagnostics and received individualized preemptive treatment. In these 3 patients, DS detected mutations in PB for >100 days preceding overt relapse and the doubling times were 14, 25 and 36 days. In conclusion, DS of leukemia-specific mutations at frequent intervals in PB enables early detection of relapse and ES at diagnosis may identify SNVs applicable for such longitudinal MRD monitoring. This approach facilitates molecular disease surveillance and initiation of preemptive therapy in AML patients without established qPCR targets. Disclosures No relevant conflicts of interest to declare.

Summary: The exact disease state of chronic myeloid leukaemia (CML) patients in deep molecular remission is unknown, because even the most sensitive quantitative reverse transcription polymerase chain reaction (qPCR) methods cannot identify patients prone to relapse after treatment withdrawal. To elucidate this, CD34 + stem cell and progenitor cell subpopulations were isolated by fluorescence-activated cell sorting (FACS), and their content of residual Philadelphia positive (Ph +) cells was evaluated in 17 CML patients (major molecular response, n = 6; 4-log reduction in BCR-ABL1 expression (MR 4), n = 11) using both sensitive qPCR and interphase fluorescence in situ hybridization (iFISH). Despite evaluating fewer cells, iFISH proved superior to mRNA-based qPCR in detecting residual Ph + stem cells (P = 0·005), and detected Ph + stem- and progenitor cells in 9/10 patients at frequencies of 2-14%. Moreover, while all qPCR + samples also were iFISH +, 9/33 samples were qPCR-/iFISH +, including all positive samples from MR 4 patients. Our findings show that residual Ph + cells are low BCR-ABL1 producers, and that DNA-based methods are required to assess the content of persisting Ph + stem cells in these patients. This approach demonstrates a clinically applicable manner of assessing residual disease at the stem cell level in CML patients in MR 4, and may enable early and safe identification of candidates for tyrosine kinase inhibitor withdrawal.

Udgivelsesdato: 2009-Nov HOXA4 gene expression is a predictor for outcome in normal karyotypic acute myeloid leukaemia (AML) patients. Given that Meis1 is a co-factor for Hox genes, we hypothesized that the combined expression of HOXA4 and MEIS1 might add prognostic information in these patients. When diagnostic samples from 246 AML patients were divided into three main groups based on gene expression levels of HOXA4 combined with MEIS1 we found that within the group of patients exhibiting low levels of HOXA4, those with a high expression of MEIS1 had a significantly worse outcome than those exhibiting low MEIS1 expression (P = 0.025). Moreover, this prediction was independent of cytogenetics, mutational status of the NPM1 and FLT3 genes as well as upon WBC and age. To evaluate the possible contribution of regulatory events underlying these observations, 157 patient samples were subjected to promoter hypermethylation analysis. We observed that 77% were HOXA4- and 15%MEIS1 hypermethylated and that this epigenetic alteration was highly correlated to the gene expression level (MEIS1: P = 0.001; HOXA4: P = 0.007). Finally, we found a higher expression level and a higher frequency of hypermethylation of HOXA4 among patients with NPM1 mutations. In conclusion, our data show that the combination of low HOXA4 and low MEIS1 gene expression is a favourable predictor for outcome in all AML patients and that the expression levels are governed by the methylation state of these genes.

Udgivelsesdato: 2008-Jun We hypothesized that Wilms tumour 1 gene (WT1) expression levels in acute myeloid leukaemia (AML) patients might have predictive value and reveal molecular relapse kinetics. WT1 level was determined at diagnosis, during therapy and post-therapy follow-up in 89 patients who reached first complete remission (CR1) (952 samples, median 8 samples/patient, range 2-38). CR1 bone marrow (BM) WT1 level above normal (based on 39 healthy donors) was an independent adverse prognostic factor regarding both disease-free survival [hazard ratio (HR) 4.46, P = 0.001] and overall survival (HR 2.62, P = 0.019). By grouping 34 BM and 99 peripheral blood (PB) complete remission samples in monthly intervals prior to clinical relapse, disease development was delineated and a simple mathematical model constructed, that allowed for the prediction of relapse detection rates (RDRs) as well as median times [t(m)s] from WT1 positivity to clinical relapse. BM sampling was required to obtain RDRs above 93% and t(m)s above 67 d. Acceptable RDRs and t(m)s (81% and 44 d, respectively) could be acquired by bimonthly PB sampling. In conclusion, CR1 WT1 expression is an independent prognostic factor in AML. According to our model, BM is superior for relapse prediction, but PB samples are useful when shorter sampling intervals are possible.

Preemptive treatment of relapse of acute myeloid leukemia (AML) holds the promise to improve the prognosis of this currently highly lethal condition. Proposed treatment modalities applicable in preemptive cytoreduction (e.g. demethylating agents or standard chemotherapy) differ substantially in interval from administration to anti-leukemic effect. The t(6;9) balanced translocation, producing the DEK-NUP214 fusion protein, is seen in only 1% of AML patients. We hypothesized that in these patients, who relapse with a very high frequency, a more detailed knowledge of leukemic relapse growth kinetics would improve the personalized decision-making regarding re-administration of chemotherapy. Based on standardized quantitative PCR data we therefore delineated the relapse kinetics in a cohort of 27 relapsing DEK-NUP214 positive patients treated in four different European countries. The pre-relapse leukemic burden increased with a median doubling time of 13 days (range: 5-51 days, median: 0.71 logs/month, range: 0.18-1.91 logs/month), with FLT3-ITD positive patients relapsing significantly faster than FLT3-ITD negative ones (median: 0.9 vs. 0.6 logs/month, Wilcoxon ranksum test, P=0.041) Peripheral blood and bone marrow were equally useful for minimal residual disease (MRD) detection and thus we found that with sampling intervals of two months, 94% of relapses would be detected with a median time from MRD detection to hematological relapse of 64 days. In conclusion, this data provide algorithms for handling the rare DEK-NUP214 positive AML patients allowing for planning of both MRD follow-up and, upon molecular relapse, the timing of cytoreduction or possibly transplant procedures. This article is protected by copyright. All rights reserved.

This chapter discusses how minimal residual disease (MRD) is detected and managed in acute myeloid leukemia (AML) patients. The most commonly used techniques to detect residual leukemia in patients in complete remission (CR) are quantitative PCR (qPCR) and multicolor flow cytometry (MFC). While qPCR techniques have been extensively validated in multicenter efforts, and MRD detection using qPCR targets RNA or DNA sequences, which are derived from fusion genes, mutated genes, or genes overexpressed in AML cells, less formalized testing has been performed with MFC. For all major MRD markers, prognosis has been shown to be affected by the MRD level after the first course of chemotherapy. The applicability of MRD markers varies considerably. The majority of AML relapses occur within the first 2 years from diagnosis. That is not to say that relapse cannot occur later; but, on closer molecular characterization, late relapses will often turn out to be cases of secondary AML.

SET domain and mariner transposase fusion gene (SETMAR), also known as Metnase, has previously been shown to suppress the formation of chromosomal translocation in mouse fibroblasts. Despite the fact that hematologic malignancies are often characterized by chromosomal rearrangements, no studies have hitherto investigated the expression pattern of the gene in these disorders. We hypothesized that a high expression of SETMAR protected the cells from chromosomal rearrangements; thus, we examined the mRNA expression of SETMAR transcript variants in hematologic patients. We identified six transcript variants (var1, var2, var5, varA, varB, varC), of which three had not been reported previously. Expression levels were quantified by transcript-specific quantitative polymerase chain reaction in 15 healthy individuals, 70 acute myeloid leukemia (AML) patients (translocation positive, n = 30 [AML TPos ], translocation negative, n = 40 [AML TNeg ]), seven patients with mantle cell lymphoma (t [11,14] positive), and 13 patients with chronic myeloid leukemia (t [9,22] positive). All variants were significantly overexpressed in both subgroups of AML compared with healthy individuals (var1 and var2: p 0.00001 for both AML subgroups, varA and varB: p = 0.0002, var5: p = 0.0008, and varC: p = 0.0001 for AML TNeg ; varA: p = 0.0048, varB and var5: p = 0.0001, varC: p = 0.0017). When comparing the expression in AML TNeg and AML TPos , we found a significantly increased expression of the full length SETMAR in AML TNeg (var1: p = 0.047), suggesting a protective effect of high SETMAR expression on formation of chromosomal translocations. In conclusion, we have found known and novel SETMAR splice variants to be significantly increased in AML. To our knowledge, this is the first study that describes an expression profile of SETMAR in subgroups of hematologic malignancies, which can be linked to the incidence of chromosomal rearrangements.

Summary: Real-time quantitative polymerase chain reaction (qPCR) has been extensively validated for the detection of minimal residual disease (MRD) in acute myeloid leukaemia (AML). Meanwhile, multicolour flow cytometry (MFC) has received less attention because the so-called leukaemia-associated immunophenotypes (LAIPs) are generally of lower sensitivity and specificity, and prone to change during therapy. To improve MRD assessment by MFC, we here evaluate the combination of human Myeloid Inhibitory C-type Lectin (hMICL, also termed C-type lectin domain family 12, member A, CLEC12A) and CD 123 (also termed interleukin-3 receptor alpha, IL3RA) in combination with CD34 and CD117 (KIT), as an MRD assay in pre-clinical and clinical testing in 69 AML patients. Spiking experiments revealed that the assay could detect MRD down to 10 -4 in normal bone marrow with sensitivities equalling those of validated qPCR assays. Moreover, it provided at least one MFC MRD marker in 62/69 patients (90%). High levels of hMICL/CD123 LAIPs at the post-induction time-point were a strong prognostic marker for relapse in patients in haematological complete remission (P < 0·001). Finally, in post induction samples, hMICL/CD123 LAIPs were strongly correlated (r = 0·676, P = 0·0008) to applied qPCR targets. We conclude the hMICL/CD123-based MFC assay is a promising MRD tool in AML.

Objectives Patients with acute myeloid leukaemia (AML) of the monocytic lineage often lack molecular markers for minimal residual disease (MRD) monitoring. The MLL-MLLT3 fusion transcript found in patients with AML harbouring t(9;11) is amenable to RT-qPCR quantification but because of the heterogeneity of translocation break points, the MLL-MLLT3 fusion gene is a challenging target. We hypothesised that MRD monitoring using MLL-MLLT3 as a RT-qPCR marker is feasible in the majority of patients with t(9;11)-positive AML. Methods Using a locked nucleic acid probe, we developed a sensitive RT-qPCR assay for quantification of the most common break point region of the MLL-MLLT3 fusion gene. Five paediatric patients with t(9;11)-positive AML were monitored using the MLL-MLLT3 assay. Results A total of 43 bone marrow (BM) and 52 Peripheral blood (PB) samples were collected from diagnosis until follow-up. Two patients relapsed, and both were MRD positive in BM after first induction course. A total of three relapses occurred, and they were detected by RT-qPCR 3 wks before haematological relapse was diagnosed. Conclusion This MLL-MLLT3 RT-qPCR assay could be useful in MRD monitoring of a group of patients with AML who often lack reliable MRD markers.

The concept of minimal residual disease in acute myeloid leukaemia has been steadily developed pre-clinically, with quantitative polymerase chain reaction (qPCR) leading the way with highly validated assays for patient-based risk stratification at post-treatment time points, which are being integrated in clinical trials both at evaluation of first complete remission (CR1) and after attaining CR1. Moreover, multicolour flow cytometry (MFC) has been increasingly employed in identifying leukaemia-associated immunophenotypes (LAIPs) with significant progress being made in standardization. In translating these widely varying methodologies to parameters useful for individualized patient decision-making, one of the obstacles has been that the assays entail varying sensitivities dependent on a number of variables. For qPCR, sensitivity depends on target type (i.e. fusion transcript, mutated gene or even overexpressed gene) and - in the case of overexpressed genes - on expression in healthy haematopoiesis. For MFC, sensitivity is likewise largely a function on whether the same phenotype is seen in normal immature cells and, in addition, antigen drift/shift with LAIPs changing at relapse is a well-known problem. In considering which sensitivity to opt for, a further variable is the situation of patient, most importantly the level of cytoreduction intended. Here we will attempt to give an overview of these pertinent questions intended for the practicing haematologist, focusing on where the field is heading at the clinical level.

Chromosome translocation 8q22;21q22 [t(8;21)] is commonly associated with acute myeloid leukemia (AML), and the resulting AML1-ETO fusion proteins are involved in the pathogenesis of AML. To identify novel molecular and therapeutic targets, we performed combined gene expression microarray and promoter occupancy (ChIP-chip) profiling using Lin−/Sca1−/cKit+ cells, the major leukemia cell population, from an AML mouse model induced by AML1-ETO9a (AE9a). Approximately 30% of the identified common targets of microarray and ChIP-chip assays overlap with the human t(8;21)–gene expression molecular signature. CD45, a protein tyrosine phosphatase and a negative regulator of cytokine/growth factor receptor and JAK/STAT signaling, is among those targets. Its expression is substantially down-regulated in leukemia cells. Consequently, JAK/STAT signaling is enhanced. Re-expression of CD45 suppresses JAK/STAT activation, delays leukemia development, and promotes apoptosis of t(8;21)–positive cells. This study demonstrates the benefit of combining gene expression and promoter occupancy profiling assays to identify molecular and potential therapeutic targets in human cancers and describes a previously unappreciated signaling pathway involving t(8;21) fusion proteins, CD45, and JAK/STAT, which could be a potential novel target for treating t(8;21) AML.

Background: Long-term patient survival in childhood acute myeloid leukemia (AML) has improved dramatically the last decades. However, 30% of children with AML die from the disease with hematological relapse being the most common event and cause of treatment failure. Early detection of imminent hematological relapse during follow-up may facilitate preparation of upcoming therapy including hematopoietic stem cell transplantation (HSCT) or an intervention e.g. preemptive therapy. Increasing levels of minimal residual disease (MRD) in peripheral blood (PB) may predict impending relapse in patients in first complete remission (CR1). Quantitative PCR (qPCR) is a highly sensitive assay suitable for MRD quantification in PB but absence and instability of valid qPCR MRD markers limit molecular detection of disease recurrence in a large proportion of patients. The Wilms tumor 1 gene (WT1) is frequently overexpressed at diagnosis in hematological malignancies but the predictive value of WT1 expression levels in childhood AML during follow-up remain uncertain. We investigated the applicability of various fusion transcripts and WT1 expression as putative MRD targets in PB disease monitoring. Methods: From January 2004 to August 2014, 135 pediatric patients were diagnosed with de novo AML and treated on two consecutive protocols, NOPHO-AML 2004 and NOPHO-DBH AML 2012, in Iceland, Finland and Denmark. Potential qPCR MRD targets were identified in 69% (93/135) of these patients. qPCR MRD were quantified in PB at scheduled time points during therapy followed by sampling every second month from end of therapy until 2 years after diagnosis or hematological relapse. qPCR MRD data were available from at least 5 time points (median samples/patient: 13, range 5-19) after induction therapy in 42 patients; RUNX1-RUNX1T1 (8), CBFβ/MYH11 (4), MLLT3/MLL (7), MLL-ENL (2), and WT1 overexpression (21). WT1 was considered overexpressed if WT1/ABL ratio was higher than 1/16 at diagnosis. Patients with both fusion transcript and WT1 overexpression were monitored using the fusion transcript as MRD target. Molecular remission (mCR) for fusion transcripts was defined as an MRD level in PB < 5x10-4. Molecular relapse was defined as a 10-fold increase in MRD to a level of at least 5x10-4. A remission baseline WT1 expression was defined as the mean of the last three WT1 levels during consolidation therapy. Molecular relapse in patients with WT1 overexpression was defined as a 10-fold increase in MRD compared to baseline WT1 expression and above normal WT1 expression range. Results: Median follow-up time in patients with fusion transcripts was 74 weeks from diagnosis (range: 20-169). Seven of 21 patients with fusion transcripts experienced molecular relapse during follow-up and all patients subsequently experienced hematological relapse. Median interval between molecular and hematological relapse was 3.4 weeks (range: 0.1-18.1). Patients in continuous mCR remained in CR1. Median follow-up time in patients with WT1 overexpression was 116 weeks from diagnosis (range: 40-169). Five of 21 patients developed hematological relapse. In all cases relapse was preceded by molecular relapse. Median interval between molecular and hematological relapse was 2.7 weeks (range: 2.0-5.9). A similar increase in WT1 expression was not detected in any long-term CR1 patients. Conclusion: Introduction of WT1 facilitates molecular disease monitoring in the vast majority of pediatric AML patients in CR1. Although numbers are small, our study indicates that both fusion transcripts and WT1 may serve as sensitive MRD targets. All patients in continuous CR1 maintained mCR throughout follow-up. All overt hematological relapses were preceded by molecular relapse though in 50% of cases the interval between molecular and hematological relapse was 3 weeks or less. Interval from molecular to hematological relapse showed great diversity in patients with fusion transcripts indicating heterogeneous relapse kinetics according to the underlying genetic lesion. A shorter interval between monitoring sampling may allow earlier detection of molecular relapse and a potential window for preemptive therapy. Disclosures No relevant conflicts of interest to declare.

Abstract 1447 Background: There is a growing realization that outcome of acute myeloid leukemia (AML) is strongly correlated to whether minimal residual disease (MRD) - as quantified by either multicolor flow cytometry (MFC) or real-time quantitative polymerase chain reaction (qPCR) - is demonstrable at crucial clinical decision time points. While FCM is applicable in up to 95% of all cases through the detection of leukemia-associated immunophenotypes (LAIPs), its major drawback is the lack of sensitivity in most cases and antigen shift, which is seen in up to 20% of cases. In contrast, while its sensitivity is generally considered to be higher than that of FCM, qPCR can only be applied in less than 80% of the patients. We have previously reported human Myeloid Inhibitory C-type Lectin (hMICL) and the interleukin-3 receptor alpha (CD123) to be potent and widely applicable markers in MRD detection by MFC, but the sensitivity of this approach compared to qPCR techniques remains to be elucidated (Clinical Cytometry, Part B, in press). Problem formulation: No previous studies have to our knowledge established the sensitivity levels of markers within these methodologies. Data from such experimentation would allow for better decision making as to what marker to apply in the given patient. Hypothesis: We hypothesized that the direct comparison between MRD technologies might yield hard data as to optimal choice of methods in the pre-clinical setting, and ultimately also for design of future FCM based MRD protocols. Results: Initially, we determined the validity of hMICL/CD123 FCM assay by performing two-fold dilution series of cryopreserved AML cells in highly purified T-cells, the latter being hMICL-/CD123-/CD34-/CD117-. Dilutions at 1: 1 to 1: 214 displayed linearity in MRD drop and resulted in a coefficient of correlation of 0.99 (P = Disclosures: No relevant conflicts of interest to declare.

An increasing body of data has demonstrated that the traditional concept of morphologic complete remission in acute myeloid leukemia, in which less than 5% myeloblasts is regarded as a sufficient response criterion, is not biologically sound. Fortunately, the quantitative reverse-transcribed polymerase chain reaction (RT-PCR) method seems to be a promising alternative because of its high degree of preclinical standardization and extreme sensitivity on the background of an accurate day-to-day estimate of sample quality. Widespread implementation of this has, however, to some extent been hampered by the lack of knowledge of how and when to measure minimal residual disease levels and, even more importantly, how to react preemptively on a molecular relapse defined by a PCR reversal. Thus, only few prospective studies have been published to date to clinically validate this assay. Here, we discuss outstanding issues in the clinical implementation of RT-PCR for fusion transcripts, mutated and overexpressed genes in acute myeloid leukemia patients in complete remission, and propose a set of guidelines, which can be used when designing prospective trials aimed at validating the use of RT-PCR as well as for following these patients based on mathematical models for disease recurrence recently developed in our laboratory.

The biology of acute myeloid leukemia (AML) is complex and includes both genetic and epigenetic aberrations. We addressed the combined consequences of promoter hypermethylation of p15, CDH1, ER, MDR1, and RARB2 and mutation of NPM1, CEBPA, FLT3, and WT1 in a Danish cohort of 70 pediatric and 383 adult AML patients.Mutation analysis was done by fragment analysis followed by sequencing or by sequencing alone. Methylation status was determined using methylation-sensitive melting curve analysis (MS-MCA) after initial bisulfite modification.Among pediatric AMLs, we found promoter hypermethylation in p15 (47%), CDH1 (64%), ER (62%), MDR1 (8%), and RARB2 (22%) and mutations in NPM1 (11%), CEBPA (3%), FLT3ITD (4%), FLT3D835 (7%), and WT1 (7%). Promoter hypermethylation was significantly more frequent in core binding factor leukemias (CBF) compared to AMLs with abnormalities involving 11q23 (P = 0.024). Compared to adult AML we found a significant difference in p15 (47% vs. 73%, P 0.001) and RARB2 (22% vs. 42%, P = 0.003) methylation, as well as in NPM1 (11% vs. 31%, P = 0.001) and FLT3ITD (4% vs. 26%, P 0.001) mutation.Age-related differences exist in the frequency of mutations and it appears that promoter hypermethylation occurs in a non-random pattern in childhood AML accompanying specific genetic aberrations, and might represent an important step in the leukemogenic transformation.

Early relapse detection in acute myeloid leukemia is possible using standardized real-time quantitative polymerase chain reaction (RQ-PCR) protocols. However, optimal sampling intervals have not been defined and are likely to vary according to the underlying molecular lesion. In 74 patients experiencing hematologic relapse and harboring aberrations amenable to RQ-PCR (mutated NPM1 [designated NPM1c], PML-RARA, RUNX1-RUNX1T1, and CBFB-MYH11), we observed strikingly different relapse kinetics. The median doubling time of the CBFB-MYH11 leukemic clone was significantly longer (36 days) than that of clones harboring other markers (RUNX1-RUNX1T1, 14 days; PML-RARA, 12 days; and NPM1c, 11 days; P < .001). Furthermore, we used a mathematical model to determine frequency of relapse detection and median time from detection of minimal residual disease to hematologic relapse as a function of sampling interval length. For example, to obtain a relapse detection fraction of 90% and a median time of 60 days, blood sampling every sixth month should be performed for CBFB-MYH11 leukemias. By contrast, in NPM1c+/FLT3-ITD−, NPM1c+/FLT3-ITD+, RUNX1-RUNX1T1, and PML-RARA leukemias, bone marrow sampling is necessary every sixth, fourth, and fourth and second month, respectively. These data carry important implications for the development of optimal RQ-PCR monitoring schedules suitable for evaluation of minimal residual disease–directed therapies in future clinical trials.

In acute myeloid leukemia (AML) mouse models, the RUNX1-RUNX1T1 fusion protein has failed to produce leukemia by itself, but alternative splicing of exon 9a of the RUNX1-RUNX1T1 fusion transcript (FT) has recently been shown to enhance the leukemogenic potential. We have analyzed 138 diagnosis and follow-up samples from 13 RUNX1-RUNX1T1+ patients as well as diagnosis samples from 13 RUNX1-RUNX1T1- AML patients and 26 healthy donors. Levels of native RUNX1T1 mRNA were low in both healthy and RUNX1-RUNX1T1-negative AML samples. Likewise, the ratio between RUNX1T1 mRNA harboring exon 9a and lacking exon 9a was low and tightly regulated (0.017-0.11). In contrast, 11/13 RUNX1-RUNX1T1-positive AML patients displayed high and variable ratios of FT ranging from 0.05 to 0.46 (P

In haematological malignancies, molecular markers like fusion DNA from balanced translocations, point mutations, or over-expressed genes can now be used not only for diagnosis, but also for determination of the minimal residual disease (MRD) after cytoreduction with a sensitivity by far exceeding that of previous methodologies. The sensitivity of quantitative polymerase chain reaction typically reaches a validated identification of 1 malignant cell in 100,000.

In haematological malignancies, molecular markers like fusion DNA from balanced translocations, point mutations, or over-expressed genes can now be used not only for diagnosis, but also for determination of the minimal residual disease (MRD) after cytoreduction with a sensitivity by far exceeding that of previous methodologies. The sensitivity of quantitative polymerase chain reaction typically reaches a validated identification of 1 malignant cell in 100,000. Udgivelsesdato: 2009-Jan-19

Purpose Risk stratification in acute myeloid leukemia (AML) is currently based on pretreatment characteristics. It remains to be established whether relapse risk can be better predicted through assessment of minimal residual disease (MRD). One proposed marker is the Wilms tumor gene WT1, which is overexpressed in most patients with AML, thus providing a putative target for immunotherapy, although in the absence of a standardized assay, its utility for MRD monitoring remains controversial. Patients and Methods Nine published and in-house real-time quantitative polymerase chain reaction WT1 assays were systematically evaluated within the European LeukemiaNet; the best-performing assay was applied to diagnostic AML samples (n = 620), follow-up samples from 129 patients treated with intensive combination chemotherapy, and 204 normal peripheral blood (PB) and bone marrow (BM) controls. Results Considering relative levels of expression detected in normal PB and BM, WT1 was sufficiently overexpressed to discriminate ≥ 2-log reduction in transcripts in 46% and 13% of AML patients, according to the respective follow-up sample source. In this informative group, greater WT1 transcript reduction after induction predicted reduced relapse risk (hazard ratio, 0.54 per log reduction; 95% CI, 0.36 to 0.83; P = .004) that remained significant when adjusted for age, WBC count, and cytogenetics. Failure to reduce WT1 transcripts below the threshold limits defined in normal controls by the end of consolidation also predicted increased relapse risk (P = .004). Conclusion Application of a standardized WT1 assay provides independent prognostic information in AML, lending support to incorporation of early assessment of MRD to develop more robust risk scores, to enhance risk stratification, and to identify patients who may benefit from allogeneic transplantation.

Udgivelsesdato: 2008-Nov-4 AML1-ETO is generated from t(8;21)(q22;q22), which is a common form of chromosomal translocation associated with development of acute myeloid leukemia (AML). Although full-length AML1-ETO alone fails to promote leukemia because of its detrimental effects on cell proliferation, an alternatively spliced isoform, AML1-ETO9a, without its C-terminal NHR3/NHR4 domains, strongly induces leukemia. However, full-length AML1-ETO is a major form of fusion product in many t(8;21) AML patients, suggesting additional molecular mechanisms of t(8;21)-related leukemogenesis. Here, we report that disruption of the zinc-chelating structure in the NHR4 domain of AML1-ETO by replacing only one critical amino acid leads to rapid onset of leukemia, demonstrating that the NHR4 domain with the intact structure generates inhibitory effects on leukemogenesis. Furthermore, we identified SON, a DNA/RNA-binding domain containing protein, as a novel NHR4-interacting protein. Knock-down of SON by siRNA resulted in significant growth arrest, and disruption of the interaction between AML1-ETO and endogenous SON rescued cells from AML1-ETO-induced growth arrest, suggesting that SON is an indispensable factor for cell growth, and AML1-ETO binding to SON may trigger signals inhibiting leukemogenesis. In t(8;21) AML patient-derived primary leukemic cells and cell lines, abnormal cytoplasmic localization of SON was detected, which may keep cells proliferating in the presence of full-length AML1-ETO. These results uncovered the crucial role of the NHR4 domain in determination of cellular fate during AML1-ETO-associated leukemogenesis.