Search

PDF file - 1.2MB

Purpose:The stromal and immune bone marrow (BM) landscape is emerging as a crucial determinant for acute myeloid leukemia (AML). Regulatory T cells (Treg) are enriched in the AML microenvironment, but the underlying mechanisms are poorly elucidated. Here, we addressed the effect of IFNγ released by AML cells in BM Treg induction and its impact on AML prognosis.Experimental Design:BM aspirates from patients with AML were subdivided according to IFNG expression. Gene expression profiles in INFγhigh and IFNγlow samples were compared by microarray and NanoString analysis and used to compute a prognostic index. The IFNγ release effect on the BM microenvironment was investigated in mesenchymal stromal cell (MSC)/AML cell cocultures. In mice, AML cells silenced for ifng expression were injected intrabone.Results:IFNγhigh AML samples showed an upregulation of inflammatory genes, usually correlated with a good prognosis in cancer. In contrast, in patients with AML, high IFNG expression was associated with poor overall survival. Notably, IFNγ release by AML cells positively correlated with a higher BM suppressive Treg frequency. In coculture experiments, IFNγhigh AML cells modified MSC transcriptome by upregulating IFNγ-dependent genes related to Treg induction, including indoleamine 2,3-dioxygenase 1 (IDO1). IDO1 inhibitor abrogated the effect of IFNγ release by AML cells on MSC-derived Treg induction. In vivo, the genetic ablation of IFNγ production by AML cells reduced MSC IDO1 expression and Treg infiltration, hindering AML engraftment.Conclusions:IFNγ release by AML cells induces an immune-regulatory program in MSCs and remodels BM immunologic landscape toward Treg induction, contributing to an immunotolerant microenvironment.See related commentary by Ferrell and Kordasti, p. 2986

Purpose: The 9p21 locus, encoding three important tumor suppressors (p16/CDKN2A, p14/ARF, and p15/CDKN2B), is a major target of inactivation in the pathogenesis of many human tumors.Patients and Methods: To explore, at high resolution, the frequency and size of alterations affecting this locus in adult BCR-ABL1–positive acute lymphoblastic leukemia (ALL) and to investigate their prognostic value, 112 patients (101 de novo and 11 relapsed cases) were analyzed by genome-wide single-nucleotide polymorphism arrays and gene candidate deep exon sequencing. Paired diagnosis–relapse samples were further available and analyzed for 19 (19%) cases.Results:CDKN2A/ARF and CDKN2B genomic alterations were identified in 29% and 25% of newly diagnosed patients, respectively. Deletions were monoallelic in 72% of cases, and in 43% of them, the minimal overlapping region of the lost area spanned only the CDKN2A/B gene locus. An analysis conducted at relapse showed an increase in the detection rate of CDKN2A/ARF loss (47%) compared with the time of diagnosis (P = 0.06). Point mutations within the 9p21 locus were found at very low levels, with only a nonsynonymous substitution in the exon 2 of CDKN2A. Of note, deletions of CDKN2A/B were significantly associated with poor outcomes in terms of overall survival (P = 0.0206), disease free-survival (P = 0.0010), and cumulative incidence of relapse (P = 0.0014).Conclusions: Inactivation of the 9p21 locus by genomic deletion is a frequent event in BCR-ABL1–positive ALL. Deletions are frequently acquired during leukemia progression and are a poor prognostic marker of long-term outcomes. Clin Cancer Res; 17(23); 7413–23. ©2011 AACR.

Supplementary Data from Release of IFNγ by Acute Myeloid Leukemia Cells Remodels Bone Marrow Immune Microenvironment by Inducing Regulatory T Cells

The presence of peripheral blasts (PB) is a negative prognostic factor in patients with primary and secondary myelofibrosis (MF) and PB ≥4% was associated with a particularly unfavorable prognosis. Ruxolitinib (RUX) is the JAK1/2 inhibitor most used for treatment of MF-related splenomegaly and symptoms. Its role has not been assessed in correlation with PB.In 794 chronic-phase MF patients treated with RUX, we evaluated the impact of baseline percentage of PB on response (spleen and symptoms responses) and outcome (RUX discontinuation-free, leukemia-free, and overall survival). Three subgroups were compared: PB-0 (no PB, 61.3%), PB-4 (PB 1%-4%, 33.5%), and PB-9 (PB 5%-9%, 5.2%).At 3 and 6 months, spleen responses were less frequently achieved by PB-4 (P = .001) and PB-9 (P = .004) compared to PB-0 patients. RUX discontinuation-free, leukemia-free, and overall survival were also worse for PB-4 and PB-9 patients (P = .001, P = .002, and P.001, respectively).Personalized approaches beyond RUX monotherapy may be useful in PB-4 and particularly in PB-9 patients.

Venetoclax (VEN) and hypomethylating agent (HMAs) regimens are emerging as the standard of care for unfit for chemotherapy acute myeloid leukemia (AML) patients, but the safety and feasibility of a total outpatient management have not been fully investigated. Fifty-nine AML patients with active disease received VEN and HMAs. Nineteen out of 59 (32.2%) patients received the first cycle as inpatients, whereas 40/59 (67.8%) patients were treated in the outpatient setting. No significant differences were observed with regard to incidence of adverse events (AEs), including tumor lysis syndrome (TLS), and the 30-day and 60-day mortality was comparable. Notably, an infectious prophylaxis inspired to that adopted during intensive chemotherapy resulted in a low infection rate with a reduced bacterial infections incidence in out- versus hospitalized patients (p .0001). The overall time of hospitalization was significantly shorter in patients who received a total outpatient treatment as compared to those who received the first cycle as inpatients (5.9 vs. 39.7 days, p .0001). Despite the adopted differences in treatment management, the efficacy was similar. These data indicate that a total outpatient management of VEN and HMAs is feasible in AML patients without negatively impacting on treatment efficacy and may yield pharmacoeconomic and quality-of-life benefits.

Key Points The semaphorin receptor PLXNC1 is an IDO1-interacting gene and a strong predictor of survival in AML.An IDO1-related immune gene signature, including PLXNC1, predicts survival in AML., Visual Abstract, The contribution of the bone marrow (BM) immune microenvironment to acute myeloid leukemia (AML) development is well-known, but its prognostic significance is still elusive. Indoleamine 2,3-dioxygenase 1 (IDO1), which is negatively regulated by the BIN1 proto-oncogene, is an interferon-γ-inducible mediator of immune tolerance. With the aim to develop a prognostic IDO1-based immune gene signature, biological and clinical data of 982 patients with newly diagnosed, nonpromyelocytic AML were retrieved from public datasets and analyzed using established computational pipelines. Targeted transcriptomic profiles of 24 diagnostic BM samples were analyzed using the NanoString’s nCounter platform. BIN1 and IDO1 were inversely correlated and individually predicted overall survival. PLXNC1, a semaphorin receptor involved in inflammation and immune response, was the IDO1-interacting gene retaining the strongest prognostic value. The incorporation of PLXNC1 into the 2-gene IDO1-BIN1 score gave rise to a powerful immune gene signature predicting survival, especially in patients receiving chemotherapy. The top differentially expressed genes between IDO1low and IDO-1high and between PLXNC1low and PLXNC1high cases further improved the prognostic value of IDO1 providing a 7- and 10-gene immune signature, highly predictive of survival and correlating with AML mutational status at diagnosis. Taken together, our data indicate that IDO1 is pivotal for the construction of an immune gene signature predictive of survival in AML patients. Given the emerging role of immunotherapies for AML, our findings support the incorporation of immune biomarkers into current AML classification and prognostication algorithms.

Purpose: The stromal and immune bone marrow (BM) landscape is emerging as a crucial determinant for acute myeloid leukemia (AML). Regulatory T cells (Treg) are enriched in the AML microenvironment, but the underlying mechanisms are poorly elucidated. Here, we addressed the effect of IFNγ released by AML cells in BM Treg induction and its impact on AML prognosis. Experimental Design: BM aspirates from patients with AML were subdivided according to IFNG expression. Gene expression profiles in INFγhigh and IFNγlow samples were compared by microarray and NanoString analysis and used to compute a prognostic index. The IFNγ release effect on the BM microenvironment was investigated in mesenchymal stromal cell (MSC)/AML cell cocultures. In mice, AML cells silenced for ifng expression were injected intrabone. Results: IFNγhigh AML samples showed an upregulation of inflammatory genes, usually correlated with a good prognosis in cancer. In contrast, in patients with AML, high IFNG expression was associated with poor overall survival. Notably, IFNγ release by AML cells positively correlated with a higher BM suppressive Treg frequency. In coculture experiments, IFNγhigh AML cells modified MSC transcriptome by upregulating IFNγ-dependent genes related to Treg induction, including indoleamine 2,3-dioxygenase 1 (IDO1). IDO1 inhibitor abrogated the effect of IFNγ release by AML cells on MSC-derived Treg induction. In vivo, the genetic ablation of IFNγ production by AML cells reduced MSC IDO1 expression and Treg infiltration, hindering AML engraftment. Conclusions: IFNγ release by AML cells induces an immune-regulatory program in MSCs and remodels BM immunologic landscape toward Treg induction, contributing to an immunotolerant microenvironment. See related commentary by Ferrell and Kordasti, p. 2986

Extranodal T-lymphoproliferative disorders or T-cell lymphomas (TLPD) are classified according to the WHO Classification (4th and upcoming 5th editions) (Swerdlow et al., IARC Press 1; Alaggio et al., Leukemia 36(7):1720-1748, 2) and to the International Consensus Classification Update (Campo et al., Blood 140(11):1229-1253, 3) upon several morphologic, phenotypic, and genetic features. None of those at present included has been characterized by primary pulmonary onset. We herein present two such cases which, to the best of our knowledge, have not been previously reported and that might represent another variant of T-cell proliferation at mucosal sites. The two cases share similar histological and phenotypic features, suggesting an origin from CD4 + effector memory T cells with the expression of a CD279/PD-1 antigen. They are both monoclonal, harbor few mutations, and show no disease progression outside the lung. They only differ concerning the local extension of the process and clinical setting. The two cases are examples of so far unreported primary pulmonary TLDP, with limited stage and low proliferative index. A possible relationship with a local yet unknown inflammatory trigger that might have favored the development of the T-cell clone cannot be ruled out.

Background Myelofibrosis (MF) is a clonal disorder of hemopoietic stem/progenitor cells (HSPCs) with high prevalence in elderly patients and mutations in three driver genes (JAK2, MPL, or CALR). Around 10–15% of patients are triple-negative (TN) for the three driver mutations and display significantly worse survival. Circulating extracellular vesicles (EVs) play a role in intercellular signaling and are increased in inflammation and cancer. To identify a biomolecular signature of TN patients, we comparatively evaluated the circulating HSPCs and their functional interplay with the microenvironment focusing on EV analysis. Methods Peripheral blood was collected from MF patients (n = 29; JAK2V617F mutation, n = 23; TN, n = 6) and healthy donors (HD, n = 10). Immunomagnetically isolated CD34+ cells were characterized by gene expression profiling analysis (GEP), survival, migration, and clonogenic ability. EVs were purified from platelet-poor plasma by ultracentrifugation, quantified using the Nanosight technology and phenotypically characterized by flow cytometry together with microRNA expression. Migration and survival of CD34+ cells from patients were also analyzed after in vitro treatments with selected inflammatory factors, i.e. (Interleukin (IL)-1β, Tumor Necrosis Factor (TNF)-α, IL6) or after co-culture with EVs from MF patients/HD. Results The absolute numbers of circulating CD34+ cells were massively increased in TN patients. We found that TN CD34+ cells show in vitro defective functions and are unresponsive to the inflammatory microenvironment. Of note, the plasma levels of crucial inflammatory cytokines are mostly within the normal range in TN patients. Compared to JAK2V617F-mutated patients, the GEP of TN CD34+ cells revealed distinct signatures in key pathways such as survival, cell adhesion, and inflammation. Importantly, we observed the presence of mitochondrial components within plasma EVs and a distinct phenotype in TN-derived EVs compared to the JAK2V617F-mutated MF patients and HD counterparts. Notably, TN EVs promoted the survival of TN CD34+ cells. Along with a specific microRNA signature, the circulating EVs from TN patients are enriched with miR-361-5p. Conclusions Distinct EV-driven signals from the microenvironment are capable to promote the TN malignant hemopoiesis and their further investigation paves the way toward novel therapeutic approaches for rare MF.

Although targeting of cell metabolism is a promising therapeutic strategy in acute myeloid leukemia (AML), metabolic dependencies are largely unexplored. We aimed to classify AML patients based on their metabolic landscape and map connections between metabolic and genomic profiles. Combined serum and urine metabolomics improved AML characterization compared with individual biofluid analysis. At intracellular level, AML displayed dysregulated amino acid, nucleotide, lipid, and bioenergetic metabolism. The integration of intracellular and biofluid metabolomics provided a map of alterations in the metabolism of polyamine, purine, keton bodies and polyunsaturated fatty acids and tricarboxylic acid cycle. The intracellular metabolome distinguished three AML clusters, correlating with distinct genomic profiles: NPM1-mutated(mut), chromatin/spliceosome-mut and TP53-mut/aneuploid AML that were confirmed by biofluid analysis. Interestingly, integrated genomic-metabolic profiles defined two subgroups of NPM1-mut AML. One was enriched for mutations in cohesin/DNA damage-related genes (NPM1/cohesin-mut AML) and showed increased serum choline + trimethylamine-N-oxide and leucine, higher mutation load, transcriptomic signatures of reduced inflammatory status and better ex-vivo response to EGFR and MET inhibition. The transcriptional differences of enzyme-encoding genes between NPM1/cohesin-mut and NPM1-mut allowed in silico modeling of intracellular metabolic perturbations. This approach predicted alterations in NAD and purine metabolism in NPM1/cohesin-mut AML that suggest potential vulnerabilities, worthy of being therapeutically explored.

Relapsed or refractory (R/R) acute myeloid leukemia (AML) has a poor prognosis, and new therapies are a major clinical need. When mutated, FLT3 drives neoplastic cell proliferation. New drugs (i.e., tyrosine kinase inhibitors, TKIs) showed effectiveness in FLT3-AML and promise to change disease history and outcome. We evaluated the benefit conferred by TKIs in terms of survival, burden of complications and surrogate endpoint of quality of life in a retrospective cohort of 49 FLT3 positive, R/R AML patients. Patients who received TKIs were compared to those treated with conventional chemotherapy. Treatment with TKIs conferred a better OS and wea associated with a lower burden and severity of adverse events. Importantly, patients who received TKIs showed reduced time of hospitalization. In conclusion, treatment with TKI in R/R FLT3-AML was related to a better survival, less and milder AEs, and shorter hospitalization.

Myelofibrosis (MF) is characterized by chronic inflammation and hyper-activation of the JAK-STAT pathway. Infections are one of the main causes of morbidity/mortality. Therapy with Ruxolitinib (RUX), a JAK1/2 inhibitor, may further increase the infectious risk. Monocytes are critical players in inflammation/immunity through cytokine production and release of bioactive extracellular vesicles. However, the functional behavior of MF monocytes, particularly during RUX therapy, is still unclear. In this study, we found that monocytes from JAK2V617F-mutated MF patients show an altered expression of chemokine (CCR2, CXCR3, CCR5) and cytokine (TNF-α-R, IL10-R, IL1β-R, IL6-R) receptors. Furthermore, their ability to produce and secrete free and extracellular vesicles-linked cytokines (IL1β, TNF-α, IL6, IL10) under lipopolysaccharides (LPS) stimulation is severely impaired. Interestingly, monocytes from RUX-treated patients show normal level of chemokine, IL10, IL1β, and IL6 receptors together with a restored ability to produce intracellular and to secrete extracellular vesicles-linked cytokines after LPS stimulation. Conversely, RUX therapy does not normalize TNF-R1/2 receptors expression and the LPS-driven secretion of free pro/anti-inflammatory cytokines. Accordingly, upon LPS stimulation, in vitro RUX treatment of monocytes from MF patients increases their secretion of extracellular vesicles-linked cytokines but inhibits the secretion of free pro/anti-inflammatory cytokines. In conclusion, we demonstrated that in MF the infection-driven response of circulating monocytes is defective. Importantly, RUX promotes their infection-driven cytokine production suggesting that infections following RUX therapy may not be due to monocyte failure. These findings contribute to better interpreting the immune vulnerability of MF and to envisaging strategies to improve the infection-driven immune response.

BACKGROUND: Many efforts have been made in the attempt to address the conundrum question of fitness definition ad prognosis prediction in elderly acute myeloid leukemia (AML) patients. Parametric definitions are expected to give an advantage in patient stratification; however, clinical examination remain de facto pivotal to formulate therapy decisions and frequently the comorbidities are empirically evaluated. METHODS: We conducted a multicenter study collecting baseline comorbidity, laboratory data, CTCAE 4.0.3 adverse events (AE), and outcome of elderly patients (>65 years old) with new onset AML who received hypomethylating agents as 1st line therapy. We tested the impact on prognosis of baseline clinical and biological risk factors. Furthermore, we evaluated a score - acute myeloid leukemia-composite model, AML-CM (Mukherjee et al, 2017) - developed in chemotherapy-eligible patients, that accounts for baseline comorbidities, laboratory parameters, age and cytogenetic-molecular risk. The study was approved by local Ethical Authority (316/2019/Oss/AOUBo). RESULTS: We collected data from 131 consecutive elderly patients who received 1 st line HMAs between January 2008 and January 2021. Patients had a median age of 76 years (IQR 72 -79). Seventy-seven out of 131 patients (58.8%) had de novo AML, 32/131 (32.8%) had secondary AML, and 11/131 (8.4%) had therapy-related AML. Out of 123 evaluable patients, 43 (34.9%) had complex karyotype, 1 (0.8%) inv(16), 59 (48.4) normal karyotype, 18 (14.7%) other alterations; 8/108 patients harbored FLT3 ITD mutation (7.4%, 23 not tested), 12/101 NPM1 mutation (11.9%, 30 not tested). Based on these data, 111 patients were evaluable for ELN2010 risk stratification; 9 over 111 patients (8.1%) were stratified in the low risk, 42/111 (37.8%) in intermediate-1 risk, 17/111(15.3%) in intermediate-2 risk, and 43/111 (38.7%) in high-risk class. As expected, most of the patients had at least one comorbidity. Particularly, baseline arrhythmia was present in 29/130 (22.1%, 1 no data), cardiovascular comorbidity in 20/130 (15.4%, 1 no data), diabetes in 20/131 (15.3%), cerebrovascular comorbidity in 11/131 (8.4%), kidney disease in 15/130 (11.5%, 1 no data), lung chronic disease 19/130 (14.6% 1 no data), hypoalbuminemia in 25/111 patients (22.5%, 20 no data). With a median follow up of 28.2 months, median overall survival (OS) of the entire cohort was 15.8 months (95% C.I. 11.2-19.4). We confirmed that patient who obtained a response (complete remission, partial response, hematological improvement) after 2 months of therapy had the best OS (figure A, median OS of 21 months for responders vs 7.4 months for non-responders, p To test the impact of comorbidities combined with cytogenetic and molecular risk, AML-CM was used. Our results indicate that AML-CM score was able to stratify prognosis in elderly patients receiving frontline HMAs (figure B, median OS in score group 1: 29.7 months, score group 2: 16.5 months, score group 3: 11.2 months, score group 4: 6.6 months, p=.038). The worse prognosis of patients with higher AML-CM score, which includes patients with increased baseline comorbidities, may be explained with a higher incidence of AEs (84.55, 116.01, 131.45, 229.3 events for 100 patients per year for score group 1,2,3, and 4, respectively) and infections (53.80, 55.10, 85.95, 140.13 events for 100 patients per year for score group 1,2,3, and 4, respectively), in patients with higher baseline comorbidities. CONCLUSION: In this study we found that baseline comorbidities, captured by AML-CM score, may define prognosis of elderly patients receiving 1st line HMAs; parametric comorbidity scores may improve our ability to predict outcome and tailor interventions. The impact of comorbidity on OS may be increased with novel and more aggressive therapy. For this reason, specific studies on functional fitness tests and geriatric assessments are highly warranted in patients receiving HMAs plus venetoclax. This work was supported by Bologna AIL. CP and AC shared last authorship. Figure 1 Figure 1. Disclosures Martinelli: Daichii Sankyo: Consultancy; Pfizer: Consultancy, Speakers Bureau; Astellas: Consultancy, Speakers Bureau; Roche: Consultancy; Abbvie: Consultancy; Stemline Therapeutics: Consultancy; Celgene /BMS: Consultancy, Speakers Bureau; Incyte: Consultancy; Jazz Pharmaceuticals: Consultancy. Cavo: Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Accommodations, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Honoraria; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES, Speakers Bureau; Adaptive Biotechnologies: Consultancy, Honoraria; GlaxoSmithKline: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bristol-Myers Squib: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Papayannidis: Pfizer, Amgen, Novartis: Honoraria. Curti: Abbvie: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Jazz Pharma: Membership on an entity's Board of Directors or advisory committees.

Introduction In the setting of clinical trials Venetoclax (VEN) combined with hypomethylating agents (HMAs) has shown fair activity in Relapsed/Refractory (R/R) AML and impressive results in newly diagnosed (ND) elderly AML patients. However, no clear guidelines are available on real-life management, especially in the outpatient setting. This study involving AML patients treated with VEN combined with HMAs aims to amelioratate physicians' knowledge about the administration of these regimens. Methods This is a single-center retrospective study involving AML patients treated with Venetoclax combined with HMAs. Data were collected in accordance with GCP and Helsinky declaration. Adverse events (AEs) were graded according to CTCAE v4.03. Survival is estimated with Kaplan-Meyer method. Results A total of 59 AML patients, 43 R/R and 16 ND, have been treated with VEN plus HMAs from March 2018 to June 2021 and completed at least 1 therapy course (range 1-9, median 2, IQR 1.0 - 4.0). The median age was 70 (range 22-88) years and 15.3 % had a documented ECOG score greater than 1. VEN was combined with azacitidine in 35/59 (59.3 %) patients and with decitabine in 22/59 (37.3 %) patients (Table 1: patient and disease characteristics). The majority of patients (40/59, 67.8 %) (28/43 R/R, 12/16 ND) received the first cycle as out-patients, 19 out of 59 (32.2 %) patients were hospitalized and used as control. No significant differences with regards to disease and patients' characteristics were observed between in- and out-patients. During the ramp-up phase only 2 cases of tumor lysis syndrome (TLS) and 5 AEs were documented. During the first course, a total of 54 AEs were recorded and experienced by 16 over 19 hospitalized patients (84.2 %) and 20 over 40 outpatients (50 %). The 30-day and 60-day mortality were 2.5% (1/40) and 20 % (8/40), respectively, among patients receiving first course as out-patents, comparable to those documented in hospitalized patients. Overall, we reported 118 AEs, of which 74 were grade III-IV and the most common were hematological 23/74 (31.1 %) or infective 41/74 (55.4 %). Regarding infections, at least one bacterial infection was experienced in 10/40 (25%) and 12/19 (63.1%) patients of the outpatient and hospitalized cohorts, respectively (p = 0.009, IC 1.37 - 19.74, OR 4.98). Pneumonia and sepsis (13 and 18 cases) were the most frequent infections. Sepsis incidence was higher among hospitalized patients (13/19, 68.4 %, vs 5/40, 12.5 %, p = 0.000029). No significant difference in infective risk was documented between R/R and ND patients (65.1 vs 50 %). Thirty-two out of 59 (54.2 %) patients experienced at least one VEN withdrawal due to treatment toxicity. Twenty out of 43 AEs requiring VEN suspensions occurred during the first cycle. Patients treated in-patient showed the tendency for a higher probability to suspend therapy due to treatment toxicity (10/19 IN vs 10/40 OUT, p = 0.04). While twenty-three out of 59 (38.9 %) patients were hospitalized for treatment complications at least once, the average number of days spent in hospital was significantly different between patients receiving the first course as outpatients as compared to those who were hospitalized (5.9 vs 39.7, respectively, p < 0.0001). With a median follow-up of 117 days (IQR 92 - 173.75) in ND patients the Overall Response Rate (ORR), defined as CR + CRi + HI, was 62.5 % (10/16), with a CR/CRi rate of 50 % (8/16) and a median OS of 247 days (95% C.I. 177.71- 316.58)(Fig 1a). In the R/R setting the ORR rate was 41.8 % (18/43), with a CR/CRi rate of 25.6 % (11/43) and a median OS of 219 days (95% C.I. 91.8 - 346.2) (Fig 2a). No differences in OS were documented between patients who underwent VEN plus HMAs outpatient and patients who underwent the first cycle hospitalized (p = 0,38) (Fig. 1b-2b). Conclusions With the limitations of a single-center retrospective study, our real-life data indicate that VEN plus HMAs is feasible in an outpatient management, with minimal TLS rate and no limiting toxicities. Of note, infections rate was acceptable, bacterial infections and sepsis risk were lower in outpatients than in hospitalized patients. There was no significant impact of the outpatient management on treatment effectiveness, with data in line with published AML cohorts. Further studies evaluating the clinical, social and economic impact of outpatient VEN-based treatments are highly warranted. Figure 1 Figure 1. Disclosures Papayannidis: Pfizer, Amgen, Novartis: Honoraria. Cavo: Adaptive Biotechnologies: Consultancy, Honoraria; GlaxoSmithKline: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Accommodations, Speakers Bureau; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES, Speakers Bureau; Novartis: Honoraria; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bristol-Myers Squib: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Curti: Jazz Pharma: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees.

Background: The presence of peripheral blasts (PB) is a negative prognostic factor in patients (pts) with primary and secondary myelofibrosis (PMF/SMF) and PB ≥4% was associated with a particularly unfavorable prognosis (Masarova L et al, Cancer 2020). Ruxolitinib (RUX) is the JAK1/2 inhibitor most used for treatment of MF-related splenomegaly and symptoms. Its role has not been assessed in correlation with PB. Aims: To evaluate the impact of PB percentage on RUX efficacy and prognosis Methods: After IRB approval, the "RUX-MF" retrospective study collected 804 RUX-treated chronic-phase (CP, defined as PB Comparisons of quantitative variables between the 3 groups were carried out by Kruskal-Wallis and Dunn's tests while association between categorical variables was tested by the χ2 test. Variables significantly associated to RUX stop/leukemic transformation (LT)/overall survival (OS) in univariate analysis (Log-rank test) were considered for multivariable analyses, carried out using the Cox regression model, with evaluation of the model's performance in terms of goodness of fit. Results: Pts were categorized according to PB at RUX start: PB-0 (no PB; n. 487, 61.3%), PB-5 (PB 1-5%; n. 283, 35.8%), and PB-9 (PB 6-9%; n. 24, 2.9%). Pts characteristics at RUX start were: median age 68.1y (24-89); males 58.1%; PMF 52.5%; JAK2, CALR and MPL mutated: 80.5%, 13.1% and 2% (4.4% triple negative), high DIPSS: 7.6%; PLT25 x10 9/l: 10.8%/16.4%; spleen length ≥10 cm: 47.8%, TSS ≥20: 60.6%; ≥1/≥2 high-risk mutation (HMR): 69/18 out of 167 evaluable (41.3%/10.8%); fibrosis grade ≥2: 77.9%; starting/cumulative RUX dose ≥15 mg BID: 61.4%/52.6%. Higher PB count was associated to high DIPSS risk (PB-0: 1.9%, PB-5: 16.2%, PB-9: 21.7%, p At 3 and 6 mos, 26.9% and 30.4% of evaluable pts achieved a SR, while 59.7% and 68.1% were in SyR, respectively. At 3 mos, SR (PB-0: 31.8%, PB-5: 20.6%, PB-9: 10%, p=0.001) and SyR (PB-0: 62.9%, PB-5: 55.5%, PB-9: 36.8%, p=0.02) were less frequently achieved by PB-5 and PB-9 pts compared to PB-0 pts. This association remained significant for SR at 6 mos (PB-0: 35%, PB-5: 23.9%, PB-9: 14.3%, p=0.006) and for both SR (p=0.003) and SyR (p=0.01) at any time. After a median RUX exposure of 1.5 y (0.1-8.9), 491 (61.8%) pts stopped RUX, 110 (13.9%) had a LT and 365 (46%) died. In univariate analysis, at 2y PB-9 pts had higher rates of RUX stop (73.9% vs 40.8% and 34.3% in PB-5 and PB-0 pts, log-rank p In multivariable analysis, PB-9 pts confirmed their association with: 1) RUX stop (HR 3.74, 95%CI 1.51-3.70, p20 (HR 1.66, 95%CI 1.05-2.61, p=0.03), and HMR≥2 (HR 2.69, 95%CI 1.26-4.47, p=0.007); 2) LT (HR 3.71, 95%CI 1.71-8.04, p Conclusions: CP-MF pts with PB>5% have a worse response to RUX and a worse outcome. Personalized approaches beyond RUX monotherapy may be useful in this context. Further clinical trials evaluating combination strategies and new drugs are required. Figure 1 Figure 1. Disclosures Palandri: Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; AOP: Membership on an entity's Board of Directors or advisory committees; Sierra Oncology: Membership on an entity's Board of Directors or advisory committees; CTI: Consultancy. Abruzzese: Bristol Myers Squibb: Consultancy, Honoraria; Incyte: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria. Iurlo: Bristol Myers Squibb: Speakers Bureau; Pfizer: Speakers Bureau; Novartis: Speakers Bureau; Incyte: Speakers Bureau. Bonifacio: Bristol Myers Squibb: Honoraria; Novartis: Honoraria; Pfizer: Honoraria; Amgen: Honoraria. Cuneo: AbbVie: Consultancy, Speakers Bureau; AstraZeneca: Consultancy, Speakers Bureau; Janssen: Consultancy, Speakers Bureau; Gilead: Consultancy, Speakers Bureau. Pane: AbbVie; Amgen; Novartis: Other: Travel, accommodation, expenses; Novartis Pharma SAS;: Research Funding; AbbVie; Amgen; Novartis, GSK , Incyte: Consultancy; AbbVie; Amgen; Novartis, GSK, Incyte: Speakers Bureau. Lemoli: Celgene: Other: Support for attending meetings and/or travel; Jazz, Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AbbVie, Daiichi Sankyo, Servier: Honoraria, Speakers Bureau. Cavo: Bristol-Myers Squib: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Honoraria; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES, Speakers Bureau; Adaptive Biotechnologies: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Accommodations, Speakers Bureau; GlaxoSmithKline: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Breccia: Novartis: Honoraria; Pfizer: Honoraria; Incyte: Honoraria; Bristol Myers Squibb/Celgene: Honoraria; Abbvie: Honoraria.

Simple Summary The introduction to clinical practice of a treatment-free remission approach in chronic myeloid leukemia patients with a stable deep molecular response highlighted how crucial it is to monitor the molecular levels of BCR–ABL1 as accurately and precisely as possible. In this context, the droplet digital PCR (ddPCR) presents an alternative methodology for such quantification. To hypothesize the introduction of this technology in routine practice, we performed a multicentric study that compares ddPCR with the standard methodology currently used. Our results demonstrate that the use of ddPCR in clinical practice is feasible and could be beneficial. Abstract BCR–ABL1 mRNA levels represent the key molecular marker for the evaluation of minimal residual disease (MRD) in chronic myeloid leukemia (CML) patients and real-time quantitative PCR (RT-qPCR) is currently the standard method to monitor it. In the era of tyrosine kinase inhibitors (TKIs) discontinuation, droplet digital PCR (ddPCR) has emerged to provide a more precise detection of MRD. To hypothesize the use of ddPCR in clinical practice, we designed a multicentric study to evaluate the potential value of ddPCR in the diagnostic routine. Thirty-seven RNA samples from CML patients and five from healthy donors were analyzed using both ddPCR QXDxTM BCR-ABL %IS Kit and LabNet-approved RT-qPCR methodologies in three different Italian laboratories. Our results show that ddPCR has a good agreement with RT-qPCR, but it is more precise to quantify BCR–ABL1 transcript levels. Furthermore, we did not find differences between duplicate or quadruplicate analysis in terms of BCR–ABL1% IS values. Droplet digital PCR could be confidently introduced into the diagnostic routine as a complement to the RT-qPCR.

Introduction A large body of evidence has increasingly demonstrated that the immune tumor microenvironment (TME) critically contributes to acute myeloid leukemia (AML) development. However, current AML prognostic classifications only rely on leukemia cell-intrinsic alterations and do not incorporate immunological markers referring to TME. Indoleamine 2,3-dioxygenase 1 (IDO1), which is negatively regulated by the BIN1 proto-oncogene, is a central mediator of immune tolerance in the AML TME. This study aimed to identify IDO1-interacting genes in the AML TME and to develop a prognostic immune gene signature. Methods Biological and clinical data of 732 patients with de novo AML treated with curative intent were retrieved from public TCGA and HOVON datasets. Patients >= 65 years were excluded from survival analyses. Co-expression analysis was performed through cBioPortal on TCGA data aiming at discovering new IDO1-interacting genes. Cox regression analysis was used to identify most survival-predicting genes in order to generate a prognostic score. Differential expression (DE) analysis was performed using the nSolver software package (NanoString Technologies, Seattle, WA). Results BIN1 and IDO1 expression were negatively correlated in HOVON cases (P Conclusions Our data identify PLXNC1 as a novel IDO1-correlated gene. A three-gene immune signature that includes PLXCN1, IDO1 and BIN1 strongly predicted clinical outcome in large AML cohorts. Moreover, IDO1 and PLXNC1 expression-based DE analysis generated an immunological signature highly predictive of prognosis. In light of the emerging role of immunotherapies for AML, our findings support the incorporation of TME-associated immune biomarkers into current AML classification and prognostication algorithms. Figure Disclosures Cavo: Jannsen, BMS, Celgene, Sanofi, GlaxoSmithKline, Takeda, Amgen, Oncopeptides, AbbVie, Karyopharm, Adaptive: Consultancy, Honoraria. Rutella:NanoString Technologies, Inc.: Research Funding; MacroGenics, Inc.: Research Funding; Kura Oncology: Research Funding.

JN and CP equally contributed Introduction In the setting of clinical trials Venetoclax (VEN) combined with hypomethylating agents (HMAs) has shown fair activity in R/R AML and impressive results in treatment-naïve elderly AML patients. However, no clear guidelines are available on real-life management, especially in the outpatient setting. This study involving R/R AML patients treated with VEN combined with HMAs aims to amelioratate physicians' knowledge about the administration of these regimens. Methods This is a single-center retrospective study involving AML patients treated with Venetoclax combined with HMAs. Data were collected in accordance with GCP and Helsinky declaration. Adverse events (AEs) were graded according to CTCAE v4.03. Survival is estimated with Kaplan-Meyer method. Results Thirty-one R/R AML patients have been treated with VEN plus HMAs from March 2018 to March 2020 and completed at least 1 therapy course (range 1-9, median 2, IQR 1.0 - 5.0) (Table 1: patients' characteristics). Seventeen out of 31 (54,8 %) had received intensive chemotherapy as induction therapy. Twenty-two patients (71 %) had already received HMAs therapy, of which 14/31 (45,2 %) as first and only previous line of therapy. VEN was combined with azacitidine in 13/31 (41,9%) and with decitabine in 18/31 patients (58.1 %). The majority of patients (22/31, 70,9%) received the first cycle as out-patients, special focus of our analysis. For clinical reasons, only 9 out of 31 (29,1 %) patients were hospitalized and were used as control. In the outpatients setting, VEN dose escalation was managed with at least a weekly laboratory and clinical monitoring and the drug was often increased more slowly to carefully prevent tumor lysis syndrome or other complications. Specifically, there has been a trend toward a ramp-up schedule different from that indicated in clinical trials in the outpatient setting in comparison with hospitalized patients (77,2 % vs 33,3 %). In term of safety, no cases of tumor lysis syndrome (TLS) and only 2 AEs were documented during ramp-up phase, both experienced by hospitalized patients. Seventeen AEs were documented during cycle 1, affecting more frequently hospitalized patients (77,9% vs 31,8 %). In the outpatient setting, the early 30-days and 60-days mortalities were 4,5 % (1/22) and 13,6 % (3/22), respectively, comparable to percentages documented in hospitalized subgroup (0% and 11,1%). Overall, with a median follow-up of 138 days (IQR 69 - 285), we reported 48 AEs, of which 28 were grade III-IV and the most common were hematological (13/28, 48,1 %) or infective (14/28, 51,8 %). Twenty out of 31 (64,5 %) patients reduced VEN dosage during treatment, of which 12/20 (60 %) due to occurring AEs, and remaining patients for azole coadministration. Eleven out of 31 (35,5 %) patients required hospitalization, specifically 3 out of 9 hospitalized patients (33,3 %) during the subsequent outpatient phase of treatment, and 8/22 (36,3 %) patients who underwent VEN therapy outpatient, of which only 2 during the first 28 days of treatment. Twenty-four and 5 AEs were followed by a VEN temporary (median duration 14 days, range 5-120) and permanent withdrawn, respectively. As for the rate of response, the Overall Response Rate (ORR) by VEN plus HMAs therapy in our R/R study population, defined as CR + CRi + HI, was 41,9 % (13/31), with a CR/CRi rate of 22,6 % (7/31). The median time to first response was 67.0 days (IQR 37.0 - 133.5) and the median duration of response was 131.0 days (IQR 89.0 - 151.0). Four out of 31 (12,9 %) patients received subsequent HSCT. The median OS was 285 days (95% C.I. 178 - 392), with no difference in OS between patients who underwent VEN plus HMAs outpatient and patients who underwent the first cycle hospitalized (p = 0,38). Conclusions With the limitations of a single-center retrospective study, our real-life data indicate that VEN plus HMAs is feasible in an outpatient management, without TLS or other limiting toxicities and with comparable early-mortality and toxicity profiles, even in the ramp-up phase and first therapeutic cycle. There was no significant impact of the outpatient management on treatment effectiveness, with data in line with published R/R AML cohorts. Further studies evaluating the clinical, social and economic impact of outpatient VEN-based treatments are highly warranted. Disclosures Papayannidis: Abbvie, Janssen, Novartis, Amgen, Pfizer:Membership on an entity's Board of Directors or advisory committees, Patents & Royalties.Cavo:Jannsen, BMS, Celgene, Sanofi, GlaxoSmithKline, Takeda, Amgen, Oncopeptides, AbbVie, Karyopharm, Adaptive:Consultancy, Honoraria. OffLabel Disclosure: In R/R AML, available data regarding the combination of VEN plus HMAs come only from retrospective studies where VEN is administered as an off-label prescription due to its widespread approval for chronic lymphocytic leukemia due to promising results obtained in treatment-naive elderly AML patients

The role of circulating microvesicles (MVs) in Myelofibrosis (MF) and Essential Thrombocythemia (ET) is far to be defined. Here we found that 1) circulating megakaryocyte-MVs were reduced in MF and ET while platelet-MVs were increased; 2) the proportion of circulating megakaryocyte- and platelet-MVs was associated with disease severity in MF; 3) ruxolitinib normalized the profile of circulating megakaryocyte- and platelet-MVs in spleen responders MF patients only. Of note, a cut-off value of 19.95% of circulating megakaryocyte-MVs predicts ruxolitinib spleen response. In light of these findings, circulating megakaryocyte/platelet-MVs may have a tissue specific diagnostic and prognostic role in MF.

Acute myeloid leukemia with myelodysplasia-related changes (AML-MRC) is a heterogeneous hematological disorder defined by morphological, genetic, and clinical features. Patients with AML-MRC often show cytogenetic changes, which are associated with poor prognosis. Straightforward criteria for AML-MRC diagnosis and a more rigorous characterization of the genetic abnormalities accompanying this disease are needed. Here we describe an informative AML-MRC case, showing two separate, but concurrent, chromothripsis events, occurred at the onset of the tumor, and originating an unbalanced t(5;7) translocation and a derivative chromosome 12 with a highly rearranged short arm. Conversely, despite chromothripsis has been often associated with genomic amplification in cancer, in this case a large marker chromosome harboring amplified sequences from chromosomes 19 and 22 arose from a stepwise mechanism. Notably, the patient also showed a TP53 mutated status, known to be associated with an increased susceptibility towards chromothripsis and a poor prognosis. Our results indicate that multiple chromothripsis events may occur early in neoplastic transformation and act in a synergistic way with progressive chromosomal alterations to determine a dramatic impact on disease outcome, as suggested by the gene expression profile analysis.

Background Aneuploidy occurs in more than 20% of acute myeloid leukemia (AML) cases and correlates with an adverse prognosis. Methods To understand the molecular bases of aneuploid acute myeloid leukemia (A‐AML), this study examined the genomic profile in 42 A‐AML cases and 35 euploid acute myeloid leukemia (E‐AML) cases. Results A‐AML was characterized by increased genomic complexity based on exonic variants (an average of 26 somatic mutations per sample vs 15 for E‐AML). The integration of exome, copy number, and gene expression data revealed alterations in genes involved in DNA repair (eg, SLX4IP, RINT1, HINT1, and ATR) and the cell cycle (eg, MCM2, MCM4, MCM5, MCM7, MCM8, MCM10, UBE2C, USP37, CK2, CK3, CK4, BUB1B, NUSAP1, and E2F) in A‐AML, which was associated with a 3‐gene signature defined by PLK1 and CDC20 upregulation and RAD50 downregulation and with structural or functional silencing of the p53 transcriptional program. Moreover, A‐AML was enriched for alterations in the protein ubiquitination and degradation pathway (eg, increased levels of UHRF1 and UBE2C and decreased UBA3 expression), response to reactive oxygen species, energy metabolism, and biosynthetic processes, which may help in facing the unbalanced protein load. E‐AML was associated with BCOR/BCORL1 mutations and HOX gene overexpression. Conclusions These findings indicate that aneuploidy‐related and leukemia‐specific alterations cooperate to tolerate an abnormal chromosome number in AML, and they point to the mitotic and protein degradation machineries as potential therapeutic targets., Aneuploid acute myeloid leukemia (A‐AML) is associated with genomic and transcriptional alterations in the cell cycle and protein degradation pathways. The upregulation of PLK1 and CDC20 and the downregulation of RAD50 and of a p53‐related signature are hallmarks of A‐AML.

Approximately 18% of acute myeloid leukemia (AML) cases express a fusion transcript. However, few fusions are recurrent across AML and the identification of these rare chimeras is of interest to characterize AML patients. Here, we studied the transcriptome of 8 adult AML patients with poorly described chromosomal translocation(s), with the aim of identifying novel and rare fusion transcripts. We integrated RNA-sequencing data with multiple approaches including computational analysis, Sanger sequencing, fluorescence in situ hybridization and in vitro studies to assess the oncogenic potential of the ZEB2-BCL11B chimera. We detected 7 different fusions with partner genes involving transcription factors (OAZ-MAFK, ZEB2-BCL11B), tumor suppressors (SAV1-GYPB, PUF60-TYW1, CNOT2-WT1) and rearrangements associated with the loss of NF1 (CPD-PXT1, UTP6-CRLF3). Notably, ZEB2-BCL11B rearrangements co-occurred with FLT3 mutations and were associated with a poorly differentiated or mixed phenotype leukemia. Although the fusion alone did not transform murine c-Kit+ bone marrow cells, 45.4% of 14q32 non-rearranged AML cases were also BCL11B-positive, suggesting a more general and complex mechanism of leukemogenesis associated with BCL11B expression. Overall, by combining different approaches, we described rare fusion events contributing to the complexity of AML and we linked the expression of some chimeras to genomic alterations hitting known genes in AML.

Somatic mutations of DNMT3A occur in about 20% of acute myeloid leukemia (AML) patients. They mostly consist in heterozygous missense mutations targeting a hotspot site at R882 codon, which exhibit a dominant negative effect and are associated with high myeloblast count, advanced age, and poor prognosis. Other types of mutations such as truncations, insertions, or single-nucleotide deletion also affect the DNMT3A gene, though with lower frequency. The present study aimed to characterize two DNMT3A gene mutations identified by next-generation sequencing (NGS), through analysis of protein stability and DNA methylation status at CpG islands. The first mutation was a single-nucleotide variant of DNMT3A at exon 20 causing a premature STOP codon (c.2385G > A; p.Trp795∗; NM_022552.4). The DNMT3A mutation load increased from 4.5% to 38.2% during guadecitabine treatment, with a dominant negative effect on CpG methylation and on protein expression. The second mutation was a novel insertion of 35 nucleotides in exon 22 of DNMT3A (NM_022552.4) that introduced a STOP codon too, after the amino acid Glu863 caused by a frameshift insertion (c.2586_2587insTCATGAATGAGAAAGAGGACATCTTATGGTGCACT; p. Thr862_Glu863fsins). The mutation, which was associated with reduced DNMT3A expression and CpG methylation, persisted at relapse with minor changes in the methylation profile and at protein level. Our data highlight the need to better understand the consequences of DNMT3A mutations other than R882 substitutions in the leukemogenic process in order to tailor patient treatments, thus avoiding therapeutic resistance and disease relapse.

Background: Monitoring of BCR-ABL1 molecular levels is essential for the management of Chronic Myeloid Leukemia (CML) patients treated with Tyrosine Kinases Inhibitors (TKIs). Real Time Quantitative PCR (RT-qPCR) is currently the standard method for assessing molecular remission (MR) in patients with CML. Recently, droplet digital PCR (ddPCR) has emerged to provide a more accurate detection of minimal residual disease (MRD). In order to hypothesize the use of this new technology in the clinical practice, in the era of TKI discontinuation, we designed a multi-centric study to evaluate the potential value of ddPCR in diagnostic routine. Aims of the study were:1) the evaluation of the agreement between the measures obtained by ddPCR and RT-qPCR and 2) the assessment of the repeatability of the two methods. Methods: Total RNA was extracted from 37 CML patients using Maxwell 16 LEV simplyRNA Blood kit (Promega), following the manufacturer's instructions. Samples were divided in 5 groups based on molecular response (MR) as follow: group 1, MR Statistical analysis: Bland-Altman analysis was performed. For the measurement of the agreement we reported the bias, which is the mean of the difference between the methods, the 95% limits of agreement and the coefficient of variation. Residual variance and coefficients of repeatability (i.e. the upper limits of a prediction interval for the absolute difference between two measurements by the same method on the same item) were computed to achieve the second endpoint. An analysis of sensitivity on the labs was also carried out. All analyses were stratified by the level of disease. Results: A total of 370 measures were included in the analysis, 185 for ddPCR and 185 for RT-qPCR divided as follow: 50 for group 1 and for group 2, 90 for group 3, 4 and 5. In Table 1 we reported the median and interquartile range (IQR) for all levels of disease. Results of the Bland-Altman analysis are shown in Table 2. The coefficients of variation, which expresses the standard deviation as a percentage of the mean, were 2.35, 2.31, 1.10, 1.34, 39.12 in group 1, 2, 3, 4 and 5 respectively. The repeatability coefficients of ddPCR were smaller than qRT-PCR across all the levels of disease, showing a slightly better precision of ddPCR (Table 2). Conclusions: Higher coefficients of variation in group 1 and 2 were probably due to a greater heterogeneity of the patients. In fact, BCR-ABL1/ABL1 levels by RT-qPCR ranged between 1.43 and 6.94 and between 0.10 and 0.25 in group 1 and in group 2 respectively (Table 1). Sensitivity analysis showed that the high coefficient of variation in group 5 can be explained almost all by the variability observed in Lab B. Coefficient of repeatability of ddPCR was always smaller than RT-qPCR for all level of disease showing a slightly better precision. Our results showed that ddPCR has a good agreement with RT-qPCR and it is more precise to quantify BCR-ABL1 transcript levels, particularly for MR 4 and MR 4.5. Thus, ddPCR may be valuable in diagnostic routine. Disclosures Fava: Novartis: Honoraria; BMS: Honoraria; Pfizer: Honoraria; Incyte: Honoraria. Martino:Bio-Rad: Employment. Saglio:Ariad: Consultancy; Incyte: Consultancy; Pfizer: Consultancy; Jansen: Consultancy; Celgene: Consultancy; Novartis: Consultancy; BMS: Consultancy. Martinelli:Roche: Consultancy; BMS: Consultancy; Novartis: Consultancy; ARIAD: Consultancy; Pfizer: Consultancy. Pane:Novartis: Membership on an entity's Board of Directors or advisory committees, Other: research founding; Janssen: Membership on an entity's Board of Directors or advisory committees; GSK: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees. Cilloni:Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees.

Chromosomal rearrangements involving 3q26 are recurrent findings in myeloid malignancies leading to MECOM overexpression, which has been associated with a very poor prognosis. Other 3q abnormalities have been reported and cryptic MECOM rearrangements have been identified in some cases. By fluorescence in situ hybridization (FISH) analysis, we investigated 97 acute myeloid leukemia/myelodysplastic syndrome patients with various 3q abnormalities to determine the role and the frequency of the involvement of MECOM. We identified MECOM rearrangements in 51 patients, most of them showed 3q26 involvement by chromosome banding analysis (CBA): inv(3)/t(3;3) (n = 26) and other balanced 3q26 translocations (t(3q26)) (n = 15); the remaining cases (n = 10) showed various 3q abnormalities: five with balanced translocations involving 3q21 or 3q25; two with homogenously staining region (hsr) on 3q; and three with other various 3q abnormalities. Complex rearrangements with multiple breakpoints on 3q, masking 3q26 involvement, were identified in cases with 3q21/3q25 translocations. Furthermore, multiple breaks were observed in two cases with t(3q26), suggesting that complex rearrangement may also occur in apparently simple t(3q26). Intrachromosomal gene amplification was another mechanism leading to MECOM overexpression in two cases with hsr on 3q. In the last three cases, FISH analysis revealed 3q26 involvement that was missed by CBA because of metaphases' suboptimal quality. All cases with MECOM rearrangements showed overexpression by real-time quantitative PCR. Finally, MECOM rearrangements can occur in patients with 3q abnormalities even in the absence of specific 3q26 involvement, underlining that their frequency is underestimated. As MECOM rearrangement has been associated with very poor prognosis, its screening should be performed in patients with any 3q abnormalities.