The mortality of COVID-19 in CML patients from 2020 until 2022: results from the EPICOVIDEHA survey.

Since the beginning of the COVID-19 pandemic, there has been an overall improvement in patient mortality. However, haematological malignancy patients continue to experience significant impacts from COVID-19, including high rates of hospitalization, intensive care unit (ICU) admissions, and mortality. In comparison to other haematological malignancy patients, individuals with chronic myeloid leukemia (CML) generally have better prognosis. This study, conducted using a large haematological malignancy patient database (EPICOVIDEHA), demonstrated that the majority of CML patients experienced mild infections. The decline in severe and critical infections over the years can largely be attributed to the widespread administration of vaccinations and the positive response they elicited. Notably, the mortality rate among CML patients was low and exhibited a downward trend in subsequent years. Importantly, our analysis provided confirmation of the effectiveness of vaccinations in CML patients.

Guideline adherence and survival of patients with candidaemia in Europe: results from the ECMM Candida III multinational European observational cohort study.

BACKGROUND: The European Confederation of Medical Mycology (ECMM) collected data on epidemiology, risk factors, treatment, and outcomes of patients with culture-proven candidaemia across Europe to assess how adherence to guideline recommendations is associated with outcomes. METHODS: In this observational cohort study, 64 participating hospitals located in 20 European countries, with the number of eligible hospitals per country determined by population size, included the first ten consecutive adults with culture-proven candidaemia after July 1, 2018, and entered data into the ECMM Candida Registry (FungiScope CandiReg). We assessed ECMM Quality of Clinical Candidaemia Management (EQUAL Candida) scores reflecting adherence to recommendations of the European Society of Clinical Microbiology and Infectious Diseases and the Infectious Diseases Society of America guidelines. FINDINGS: 632 patients with candidaemia were included from 64 institutions. Overall 90-day mortality was 43% (265/617), and increasing age, intensive care unit admission, point increases in the Charlson comorbidity index score, and Candida tropicalis as causative pathogen were independent baseline predictors of mortality in Cox regression analysis. EQUAL Candida score remained an independent predictor of mortality in the multivariable Cox regression analyses after adjusting for the baseline predictors, even after restricting the analysis to patients who survived for more than 7 days after diagnosis (adjusted hazard ratio 1·08 [95% CI 1·04-1·11; p<0·0001] in patients with a central venous catheter and 1·09 [1·05-1·13; p<0·0001] in those without one, per one score point decrease). Median duration of hospital stay was 15 days (IQR 4-30) after diagnosis of candidaemia and was extended specifically for completion of parenteral therapy in 100 (16%) of 621 patients. Initial echinocandin treatment was associated with lower overall mortality and longer duration of hospital stay among survivors than treatment with other antifungals. INTERPRETATION: Although overall mortality in patients with candidaemia was high, our study indicates that adherence to clinical guideline recommendations, reflected by higher EQUAL Candida scores, might increase survival. New antifungals, with similar activity as current echinocandins but with longer half-lives or oral bioavailability, are needed to reduce duration of hospital stay. FUNDING: Scynexis.

Nirmatrelvir/ritonavir in COVID-19 patients with haematological malignancies: a report from the EPICOVIDEHA registry.

Background: Nirmatrelvir/ritonavir treatment decreases the hospitalisation rate in immunocompetent patients with COVID-19, but data on efficacy in patients with haematological malignancy are scarce. Here, we describe the outcome of nirmatrelvir/ritonavir treatment in a large cohort of the latter patients. Methods: This is a retrospective cohort study from the multicentre EPICOVIDEHA registry (NCT04733729) on patients with haematological malignancy, who were diagnosed with COVID-19 between January and September 2022. Patients receiving nirmatrelvir/ritonavir were compared to those who did not. A logistic regression was run to determine factors associated with nirmatrelvir/ritonavir administration in our sample. Mortality between treatment groups was assessed with Kaplan-Meier survival plots after matching all the patients with a propensity score. Additionally, a Cox regression was modelled to detect factors associated with mortality in patients receiving nirmatrelvir/ritonavir. Findings: A total of 1859 patients were analysed, 117 (6%) were treated with nirmatrelvir/ritonavir, 1742 (94%) were treated otherwise. Of 117 patients receiving nirmatrelvir/ritonavir, 80% had received ≥1 anti-SARS-CoV-2 vaccine dose before COVID-19 onset, 13% of which received a 2nd vaccine booster. 5% were admitted to ICU. Nirmatrelvir/ritonavir treatment was associated with the presence of extrapulmonary symptoms at COVID-19 onset, for example anosmia, fever, rhinitis, or sinusitis (aOR 2.509, 95%CI 1.448-4.347) and 2nd vaccine booster (aOR 3.624, 95%CI 1.619-8.109). Chronic pulmonary disease (aOR 0.261, 95%CI 0.093-0.732) and obesity (aOR 0.105, 95%CI 0.014-0.776) were not associated with nirmatrelvir/ritonavir use. After propensity score matching, day-30 mortality rate in patients treated with nirmatrelvir/ritonavir was 2%, significantly lower than in patients with SARS-CoV-2 directed treatment other than nirmatrelvir/ritonavir (11%, p = 0.036). No factor was observed explaining the mortality difference in patients after nirmatrelvir/ritonavir administration. Interpretation: Haematological malignancy patients were more likely to receive nirmatrelvir/ritonavir when reporting extrapulmonary symptoms or 2nd vaccine booster at COVID-19 onset, as opposed to chronic pulmonary disease and obesity. The mortality rate in patients treated with nirmatrelvir/ritonavir was lower than in patients with targeted drugs other than nirmatrelvir/ritonavir. Funding: EPICOVIDEHA has received funds from Optics COMMIT (COVID-19 Unmet Medical Needs and Associated Research Extension) COVID-19 RFP program by GILEAD Science, United States (Project 2020-8223).

Outcome of COVID-19 in allogeneic stem cell transplant recipients: Results from the EPICOVIDEHA registry.

Background: The outcome of COVID-19 in allogeneic hematopoietic stem cell transplantation (HSCT) recipients is almost uniformely considered poor. The aim of present study was to retrospectively analyse the outcome and risk factors for mortality in a large series of patients who developed COVID-19 infection after an allogeneic HSCT. Methods: This multicenter retrospective study promoted by the European Hematology Association - Infections in Hematology Study Working Group, included 326 adult HSCT patients who had COVID-19 between January 2020 and March 2022. Results: The median time from HSCT to the diagnosis of COVID-19 was 268 days (IQR 86-713; range 0-185 days). COVID-19 severity was mild in 21% of the patients, severe in 39% and critical in 16% of the patients. In multivariable analysis factors associated with a higher risk of mortality were, age above 50 years, presence of 3 or more comorbidities, active hematologic disease at time of COVID-19 infection, development of COVID-19 within 12 months of HSCT, and severe/critical infections. Overall mortality rate was 21% (n=68): COVID-19 was the main or secondary cause of death in 16% of the patients (n=53). Conclusions: Mortality in HSCT recipients who develop COVID-19 is high and largely dependent on age, comorbidities, active hematologic disease, timing from transplant and severity of the infection.

Clinical Impact of Polymerase Chain Reaction-Based Aspergillus and Azole Resistance Detection in Invasive Aspergillosis: A Prospective Multicenter Study.

BACKGROUND: Invasive aspergillosis (IA) by a triazole-resistant Aspergillus fumigatus is associated with high mortality. Real-time resistance detection will result in earlier initiation of appropriate therapy. METHODS: In a prospective study, we evaluated the clinical value of the AsperGenius polymerase chain reaction (PCR) assay in hematology patients from 12 centers. This PCR assay detects the most frequent cyp51A mutations in A. fumigatus conferring azole resistance. Patients were included when a computed tomography scan showed a pulmonary infiltrate and bronchoalveolar fluid (BALf) sampling was performed. The primary end point was antifungal treatment failure in patients with azole-resistant IA. RESULTS: Of 323 patients enrolled, complete mycological and radiological information was available for 276 (94%), and probable IA was diagnosed in 99/276 (36%). Sufficient BALf for PCR testing was available for 293/323 (91%). Aspergillus DNA was detected in 116/293 (40%) and A. fumigatus DNA in 89/293 (30%). The resistance PCR was conclusive in 58/89 (65%) and resistance detected in 8/58 (14%). Two had a mixed azole-susceptible/azole-resistant infection. In the 6 remaining patients, treatment failure was observed in 1. Galactomannan positivity was associated with mortality (P = .004) while an isolated positive Aspergillus PCR was not (P = .83). CONCLUSIONS: Real-time PCR-based resistance testing may help to limit the clinical impact of triazole resistance. In contrast, the clinical impact of an isolated positive Aspergillus PCR on BALf seems limited. The interpretation of the EORTC/MSGERC PCR criterion for BALf may need further specification (eg, minimum cycle threshold value and/or PCR positive on >1 BALf sample).

COVID-19 in adult acute myeloid leukemia patients: a long-term follow-up study from the European Hematology Association survey (EPICOVIDEHA).

Patients with acute myeloid leukemia (AML) are at high risk of dying from coronavirus disease 2019 (COVID-19). The optimal management of AML patients with COVID-19 has not been established. Our multicenter study included 388 adult AML patients diagnosed with COVID-19 between February 2020 and October 2021. The vast majority were receiving or had received AML treatment in the preceding 3 months. COVID-19 was severe in 41.2% and critical in 21.1% of cases. The chemotherapeutic schedule was modified in 174 patients (44.8%), delayed in 68 and permanently discontinued in 106. After a median follow-up of 325 days, 180 patients (46.4%) had died; death was attributed to COVID-19 (43.3%), AML (26.1%) or to a combination of both (26.7%), whereas in 3.9% of cases the reason was unknown. Active disease, older age, and treatment discontinuation were associated with death, whereas AML treatment delay was protective. Seventy-nine patients had a simultaneous AML and COVID-19 diagnosis, with better survival when AML treatment could be delayed (80%; P<0.001). Overall survival in patients with a diagnosis of COVID-19 between January 2020 and August 2020 was significantly lower than that in patients diagnosed between September 2020 and February 2021 and between March 2021 and September 2021 (39.8% vs. 60% vs. 61.9%, respectively; P=0.006). COVID-19 in AML patients was associated with a high mortality rate and modifications of therapeutic algorithms. The best approach to improve survival was to delay AML treatment, whenever possible.

Guidance of empirical antimicrobial therapy by surveillance cultures in high-risk neutropenic patients: a retrospective cohort study.

BACKGROUND: In neutropenic patients, bloodstream infections (BSI) significantly contribute to morbidity and mortality. Appropriate empirical antibiotic therapy (EAT) of BSI is essential, at the same time overconsumption of very broad-spectrum antibiotics should be avoided. We investigated: (1) whether surveillance cultures can predict BSI with third-generation cephalosporin -resistant Enterobacterales and Pseudomonas aeruginosa (3GC-R), (2) the effect of inappropriate empirical antimicrobial therapy (IEAT) on clinical outcome and (3) the potential reduction of carbapenem use when using surveillance cultures to guide therapy. METHODS: Retrospective study of adult patients with haematological malignancies with febrile episodes during chemotherapy-induced high-risk neutropenia in whom surveillance cultures were collected weekly. IEAT was defined as the absence of in vitro susceptibility of blood-isolates to the administered EAT. Clinical outcome (ICU admission and death) was evaluated within 30 days. RESULTS: A total of 673 febrile episodes occurred among 372 high-risk neutropenic patients. BSI was present in 20.1% (135/673), of which 25.9% (35/135) were due to Enterobacterales and P. aeruginosa. Of these, 17/35 were 3GC-R and 70.6% (12/17) were preceded by 3GC-R colonization. Negative predictive value of surveillance cultures for 3GC-R BSI was 99.1%. IEAT due to (3GC-R) BSI was not significantly associated with clinical outcome. Using surveillance cultures to guide EAT could potentially reduce carbapenem use by 82.8%, when compared to standard EAT with carbapenem. CONCLUSIONS: This retrospective analysis shows that in patients with high-risk neutropenia, surveillance cultures can potentially reduce the use of carbapenems with infrequent IEAT for 3GC-R BSI and no negative impact on clinical outcome.

Third-generation cephalosporin resistant gram-negative bacteraemia in patients with haematological malignancy; an 11-year multi-centre retrospective study.

OBJECTIVES: Among patients with haematological malignancy, bacteraemia is a common complication during chemotherapy-induced neutropenia. Resistance of gram-negative bacteria (GNB) to third-generation cephalosporins (3GC) is increasing. In order to explore the value of using surveillance cultures to guide empirical treatment e.g. choosing between carbapenem versus ceftazidime- we aimed to assess the distribution of pathogens causing bacteraemia in patients with haematological malignancy, and the proportion of 3GC-resistant GNB (3GC-R GNB) bacteraemia that was preceded by 3GC-R GNB colonization. METHODS: Using 11 years of data (2008-2018) from the Dutch national antimicrobial resistance surveillance system, we assessed the prevalence of 3GC-R GNB in episodes of bacteraemia, and the proportion of 3GC-R GNB bacteraemia that was preceded by 3GC-R GNB colonization. Colonization was defined as availability of any GNB surveillance isolate in the year before, independent of the causative micro-organism (time-paired isolates). RESULTS: We included 3887 patients, representing 4142 episodes of bacteraemia. GNB were identified in 715/4142 (17.3%), of which 221 (30.9%) were 3GC-R GNB. In 139 of these 221 patients a time-paired surveillance culture was available. In 76.2% (106/139) of patients these surveillance cultures already showed 3GC-R GNB isolates in the year prior to the culture date of the 3GC-R GNB positive blood isolate. CONCLUSIONS: This multi-centre study shows that in patients with haematological malignancy, the majority of 3GC-R GNB bacteraemia is preceded by 3GC-R GNB colonization. Prospective clinical studies are needed to assess the safety and benefits of the use of surveillance-cultures to guide empirical therapy to restrict the empirical use of carbapenems in this population.

Breakthrough COVID-19 in vaccinated patients with hematologic malignancies: results from the EPICOVIDEHA survey.

Limited data are available on breakthrough COVID-19 in patients with hematologic malignancy (HM) after anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination. Adult patients with HM, ≥1 dose of anti-SARS-CoV-2 vaccine, and breakthrough COVID-19 between January 2021 and March 2022 were analyzed. A total of 1548 cases were included, mainly lymphoid malignancies (1181 cases, 76%). After viral sequencing in 753 cases (49%), the Omicron variant was prevalent (517, 68.7%). Most of the patients received ≤2 vaccine doses before COVID-19 (1419, 91%), mostly mRNA-based (1377, 89%). Overall, 906 patients (59%) received COVID-19-specific treatment. After 30-day follow-up from COVID-19 diagnosis, 143 patients (9%) died. The mortality rate in patients with the Omicron variant was 7.9%, comparable to other variants, with a significantly lower 30-day mortality rate than in the prevaccine era (31%). In the univariable analysis, older age (P < .001), active HM (P < .001), and severe and critical COVID-19 (P = .007 and P < .001, respectively) were associated with mortality. Conversely, patients receiving monoclonal antibodies, even for severe or critical COVID-19, had a lower mortality rate (P < .001). In the multivariable model, older age, active disease, critical COVID-19, and 2-3 comorbidities were correlated with a higher mortality, whereas monoclonal antibody administration, alone (P < .001) or combined with antivirals (P = .009), was protective. Although mortality is significantly lower than in the prevaccination era, breakthrough COVID-19 in HM is still associated with considerable mortality. Death rate was lower in patients who received monoclonal antibodies, alone or in combination with antivirals.

Short versus extended treatment with a carbapenem in patients with high-risk fever of unknown origin during neutropenia: a non-inferiority, open-label, multicentre, randomised trial.

BACKGROUND: Early antibiotic discontinuation has been advocated in haematology patients with fever of unknown origin during chemotherapy-induced neutropenia, but its safety is unknown. We aimed to assess if short treatment with carbapenems is non-inferior to extended treatment. METHODS: This non-inferiority, open-label, multicentre, randomised trial was done in six hospitals in the Netherlands. Adult patients (≥18 years) who were treated with intensive chemotherapy or haematopoietic stem-cell transplantation (HSCT) for a haematological malignancy, and had fever of unknown origin during high-risk neutropenia (<0·5 × 109/L expected for ≥7 days) were eligible. After onset of fever, patients received either 500 mg intravenous imipenem-cilastatin four times a day or 1000 mg intravenous meropenem three times a day. Between 48 h and 72 h of treatment, participants were randomly assigned (1:1) by a computer-generated sequence to receive a short-term (72 h [60-84]; short treatment group) or extended (≥9 days until being afebrile for 5 days or neutrophil recovery; extended treatment group) carbapenem regimen. The composite primary endpoint was treatment failure, defined as recurrent fever or a carbapenem-sensitive infection between day 4 and day 9 and septic shock or respiratory failure or death from day 4 until neutrophil recovery. The study was designed to assess the non-inferiority of the short treatment compared with the extended treatment regimen, with a non-inferiority margin of 10%. The primary outcome was adjudicated by an independent outcome committee, who were masked to treatment allocation, and was analysed in the intention-to-treat and per-protocol populations. The trial is completed and registered with ClinicalTrials.gov, NCT02149329. FINDINGS: Between Dec 1, 2014, and July 1, 2019, 281 patients were included in the intention-to-treat analysis: 144 (51%) patients were assigned to the short treatment group and 137 (49%) to the extended treatment group. Median age was 59 years (IQR 52-65); 109 (39%) patients were women and 172 (61%) were men; 205 (73%) patients received HSCT. In the intention-to-treat analysis, 28 (19%) of 144 patients in the short treatment group versus 21 (15%) of 137 patients in the extended treatment group had treatment failure (adjusted risk difference [ARD] 4·0% [90% CI -1·7% to 9·7%]; p=0·25). In the per-protocol analysis (n=225), 24 (23%) of 104 patients in the short treatment group and 19 (16%) of 121 patients in the extended treatment group had treatment failure (ARD 7·3% [0·3% to 14·9%]; p=0·11). The most common grade 3-5 infection-related adverse events were mucositis (23 [20%] of 114 adverse events in the short treatment group vs 28 [29%] of 98 adverse events in the extended treatment group), fever of unknown origin (20 [18%] vs 16 [16%] events), and bacteraemia (15 [13%] vs 13 [13%] events). The number of serious adverse events were higher in the short treatment group (23 [16%] of 144 patients) than in the extended treatment group (14 [10%] of 137 patients), due to an increased rate of readmission (17 [12%] patients in the short treatment group vs ten [7%] in the extended treatment group). Death before 30 days after neutrophil recovery occurred in five (3%) participants in the short treatment group: two due to progressive leukaemia, two due to candidaemia, and one due to Enterococcus faecium bacteraemia and drug-induced pneumonitis. One (1%) patient died in the extended treatment group due to candidaemia. None of the deaths were related to carbapenem-sensitive infections. INTERPRETATION: Early discontinuation of carbapenem treatment in patients with febrile neutropenia of unknown origin does not result in increased treatment failure. Our study supports short treatment if patients are afebrile after 3 days of carbapenem treatment. However, because secondary analyses suggested that serious adverse events and all-cause mortality occurred more often in patients who are persistantly febrile the short treatment group, we recommend vigilance for non-susceptible pathogens and early resumption of empirical therapy in patients who are deteriorating. FUNDING: The Netherlands Organisation for Health Research and Development and Fonds NutsOhra.

Antifungal prophylaxis in adult patients with acute myeloid leukaemia treated with novel targeted therapies: a systematic review and expert consensus recommendation from the European Hematology Association.

On the basis of improved overall survival, treatment guidelines strongly recommend antifungal prophylaxis during remission induction chemotherapy for patients with acute myeloid leukaemia. Many novel targeted agents are metabolised by cytochrome P450, but potential drug-drug interactions (DDIs) and the resulting risk-benefit ratio have not been assessed in clinical trials, leading to uncertainty in clinical management. Consequently, the European Haematology Association commissioned experts in the field of infectious diseases, haematology, oncology, clinical pharmacology, and methodology to develop up-to-date recommendations on the role of antifungal prophylaxis and management of pharmacokinetic DDIs with triazole antifungals. A systematic literature review was performed according to Cochrane methods, and recommendations were developed by use of the Grading of Recommendations Assessment, Development and Evaluation Evidence to Decision framework. We searched MEDLINE, Embase, and Cochrane Library, including Central Register of Controlled Trials, for randomised controlled trials and systematic reviews published from inception to March 10, 2020. We excluded studies that were not published in English. Evidence for any identified novel agent that is active against acute myeloid leukaemia was reviewed for the following outcomes: incidence of invasive fungal disease, prolongation of hospitalisation, days spent in intensive-care unit, mortality due to invasive fungal disease, quality of life, and potential DDIs. Recommendations and consensus statements were compiled for each targeted drug for patients with acute myeloid leukaemia and each specific setting. Evidence-based recommendations were developed for hypomethylating agents, midostaurin, and the venetoclax-hypomethylating agent combination. For all other agents, consensus statements were given for specific therapeutic settings, specifically for the management of patients with relapsed or refractory acute myeloid leukaemia, monotherapy, and combination with chemotherapy. Antifungal prophylaxis is recommended with moderate strength in most settings, and strongly recommended if the novel acute myeloid leukaemia agent is administered in combination with intensive induction chemotherapy. For ivosidenib, lestaurtinib, quizartinib, and venetoclax, we moderately recommend adjusting the dose of the antileukaemic agent during administration of triazoles. This is the first guidance supporting clinical decision making on antifungal prophylaxis in recipients of novel targeted drugs for acute myeloid leukaemia. Future studies including therapeutic drug monitoring will need to determine the role of dosage adjustment of novel antileukaemic drugs during concomitant administration of CYP3A4-inhibiting antifungals with respect to adverse effects and remission status.

The impact of the updated EORTC/MSG criteria on the classification of hematological patients with suspected invasive pulmonary aspergillosis.

OBJECTIVES: Our aim was to evaluate the effect of the updated European Organization for Research and Treatment of Cancer (EORTC) and Mycoses Study Group 2019 definitions for invasive pulmonary aspergillosis (IPA) on patient classification and the related all-cause 12-week mortality. METHODS: In this retrospective cohort study from our tertiary care centre, we reclassified patients with haematological malignancy who underwent bronchoalveolar lavage between 2014 and 2019 for suspected IPA using the novel EORTC 2019 criteria. We performed receiver operating characteristic curve analysis to define the optimal cut-off for positive PCR and galactomannan and present survival analyses and their possible association with these diagnostic criteria through post hoc comparisons with log rank and Cox regression. RESULTS: From 323 episodes of suspected IPA in 282 patients, 73 were reclassified: 31 (42.5%) from possible to probable IPA, 5 (6.8%) from EORTC criteria not met to probable IPA, and 37 (50.7%) from EORTC criteria not met to possible IPA. Probable IPA increased therefore 11.1% (64/323, 19.8% to 100/323, 30.9%), mostly due to positive PCR (31/36, 86.1%). There was no difference in mortality between newly defined possible and probable IPA (log rank p = 0.950). Mortality was higher in probable cases with lower cycle thresholds (Ct values) versus higher Ct values (p = 0.004). Receiver operating characteristic curve analysis showed an optimal Ct value cut-off of 36.8 with a sensitivity of 75% (95% CI 64.9%-85.1%) and a specificity of 61.7% (95% CI 53.5-69.9) for 12-week mortality. DISCUSSION: The new EORTC criteria led to 11.1% more probable IPA diagnoses, mostly due to Aspergillus PCR. Restricting positive PCR to below a certain threshold might improve the discrimination of the new EORTC IPA categories for mortality.

The diagnosis and treatment of invasive aspergillosis in Dutch haematology units facing a rapidly increasing prevalence of azole-resistance. A nationwide survey and rationale for the DB-MSG 002 study protocol.

Patients with haematological malignancies are at risk for invasive fungal diseases (IFD). A survey was conducted in all Dutch academic haematology centres on their current diagnostic, prophylactic and therapeutic approach towards IFD in the context of azole-resistance. In all 8 centres, a haematologist and microbiologist filled in the questionnaire that focused on different subgroups of haematology patients. Fungal prophylaxis during neutropaenia was directed against Candida and consisted of fluconazole and/or amphotericin B suspension. Mould-active prophylaxis was given to acute myeloid leukaemia patients during chemotherapy in 2 of 8 centres. All centres used azole prophylaxis in a subset of patients with graft-versus-host disease. A uniform approach towards the diagnosis and treatment of IFD and in particular azole-resistant Aspergillus fumigatus was lacking. In 2017, all centres agreed to implement a uniform diagnostic and treatment algorithm regarding invasive aspergillosis with a central role for comprehensive diagnostics and PCR-based detection of azole-resistance. This study (DB-MSG 002) will re-evaluate this algorithm when 280 patients have been treated. A heterogeneous approach towards antifungal prophylaxis, diagnosis and treatment was apparent in the Netherlands. Facing triazole-resistance, consensus was reached on the implementation of a uniform diagnostic approach in all 8 centres.

The DNA methylation inhibitor induces telomere dysfunction and apoptosis of leukemia cells that is attenuated by telomerase over-expression.

DNA methyltransferase inhibitors (DNMTIs) such as 5-azacytidine (5-AZA) have been used for treatment of acute myeloid leukemia (AML) and other malignancies. Although inhibiting global/gene-specific DNA methylation is widely accepted as a key mechanism behind DNMTI anti-tumor activity, other mechanisms are likely involved in DNMTI's action. Because telomerase reverse transcriptase (TERT) plays key roles in cancer through telomere elongation and telomere lengthening-independent activities, and TERT has been shown to confer chemo- or radio-resistance to cancer cells, we determine whether DNMTIs affect telomere function and whether TERT/telomerase interferes with their anti-cancer efficacy. We showed that 5-AZA induced DNA damage and telomere dysfunction in AML cell lines by demonstrating the presence of 53-BP1 foci and the co-localization of 53-BP1 foci with telomere signals, respectively. Telomere dysfunction was coupled with diminished TERT expression, shorter telomere and apoptosis in 5-AZA-treated cells. However, 5-AZA treatment did not lead to changes in the methylation status of subtelomere regions. Down-regulation of TERT expression similarly occurred in primary leukemic cells derived from AML patients exposed to 5-AZA. TERT over-expression significantly attenuated 5-AZA-mediated DNA damage, telomere dysfunction and apoptosis of AML cells. Collectively, 5-AZA mediates the down-regulation of TERT expression, and induces telomere dysfunction, which consequently exerts an anti-tumor activity.

Normal hematopoietic stem cells within the AML bone marrow have a distinct and higher ALDH activity level than co-existing leukemic stem cells.

Persistence of leukemic stem cells (LSC) after chemotherapy is thought to be responsible for relapse and prevents the curative treatment of acute myeloid leukemia (AML) patients. LSC and normal hematopoietic stem cells (HSC) share many characteristics and co-exist in the bone marrow of AML patients. For the development of successful LSC-targeted therapy, enabling eradication of LSC while sparing HSC, the identification of differences between LSC and HSC residing within the AML bone marrow is crucial. For identification of these LSC targets, as well as for AML LSC characterization, discrimination between LSC and HSC within the AML bone marrow is imperative. Here we show that normal CD34+CD38- HSC present in AML bone marrow, identified by their lack of aberrant immunophenotypic and molecular marker expression and low scatter properties, are a distinct sub-population of cells with high ALDH activity (ALDH(bright)). The ALDH(bright) compartment contains, besides normal HSC, more differentiated, normal CD34+CD38+ progenitors. Furthermore, we show that in CD34-negative AML, containing solely normal CD34+ cells, LSC are CD34- and ALDH(low). In CD34-positive AML, LSC are also ALDH(low) but can be either CD34+ or CD34-. In conclusion, although malignant AML blasts have varying ALDH activity, a common feature of all AML cases is that LSC have lower ALDH activity than the CD34+CD38- HSC that co-exist with these LSC in the AML bone marrow. Our findings form the basis for combined functionally and immunophenotypically based identification and purification of LSC and HSC within the AML bone marrow, aiming at development of highly specific anti-LSC therapy.