WHO-defined Essential Thrombocythemia Research Articles

Perioperative Outcomes and Management in Patients with Myeloproliferative Neoplasms: A Multicentric Retrospective Analysis of 354 Surgical Interventions

Background: Classic myeloproliferative neoplasms (MPN) polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF), are characterized by concurrent risk of thrombotic and hemorrhagic complications. These risks are reported to be further compounded perioperatively ( Blood, 2008), though scarce contemporary data exist. Further, the lack of evidence-based guidelines leads to heterogeneous management. The objective of this study was to comparatively assess perioperative complication rates (thrombotic, hemorrhagic, and survival) and management practices in a large MPN population. Methods: Consecutive surgical interventions in patients with WHO-defined PV, ET and MF recruited from the Quebec MPN Research Group Registry (6 centers; between 1986-2023) were analyzed. Endpoints (90 days post-surgery) and surgical definitions were per convention. Standard statistics were used (JMP® Pro 14.1.0 software; SAS Institute, Cary, NC, USA). Results: A total of 354 procedures were captured in 184 patients: PV, n=87 (47%); ET, n=66 (36%); MF, n=31 (17%). Cardiovascular risks were balanced; previous venous thrombosis was enriched in PV (p=0.04; Table 1A). Major surgeries were performed in 45 cases (30%), primarily PV (p=0.004); most being general (69%) (Table 1B). Interventions were urgent in 41 cases (28%); 49 (42%) of 195 evaluable were under general anesthesia. The majority of PV/ET subjects continued antiplatelet and cytoreductive agents peri-intervention, though cytoreduction was stopped in 12-22%. Thromboprophylaxis was administered in n=42 (23%). Surgical bleeding occurred in n=8 (2%). At 90-day follow-up, arterial/venous thrombosis occurred each in n=3 (1%), hemorrhage in n=25 (8%), and death in n=4 (1%). Overall complication rate was 12% (n=40). PV patients displayed significantly higher rates of surgical bleeding (6%; p=0.0006) and perioperative hemorrhage (13%; p=0.04). Factors impacting 90-day surgical outcomes: Hemorrhage-free survival (HFS): PV: General anaesthesia (p=0.04) and antithrombotic prophylaxis (p=0.05) negatively impacted HFS on multivariate testing (Table 2). ET: Driver mutation status CALR vs JAK2 (HR 24.6; 95% CI 1.2-504; p=0.05) and urgent interventions (HR 11.5; 95% CI 0.93-144; p=0.03) emerged as independent predictors for HFS. MF: Discontinuation of antiplatelet agents perioperatively was the sole factor impacting HFS (p=0.01). Perioperative complication-free survival (CFS; composite endpoint): PV: While several factors were significant on univariate testing (procedure, leukocytosis, ruxolitinib exposure, cytoreduction modification, thromboprophylaxis), multivariate testing disclosed only lower hematocrit (< 35%; p=0.05) to impact complication rates. ET: Urgent (p<0.0001) and major procedures (p=0.009), thromboprophylaxis use (p=0.001), platelet count > 450 x 10 9/L (p=0.02), and absence of antiplatelet (p=0.02) were significant independent predictors of CFS. MF: Antiplatelet discontinuation (HR 6.5; 95% CI 0.8-50.4; p=0.02), nature of cytoreduction (ruxolitinib vs hydrea; p=0.04) and cytoreduction discontinuation pre-operatively (p=0.006) negatively impacted CFS on multivariate analysis. Limited informative events for thrombosis/survival precluded analyses. Conclusions: This is, to our knowledge, the largest and most contemporary analysis of surgical procedures in patients with MPN. Firstly, it confirms prevalent bleeding perioperatively, though balanced by fewer thrombotic events, calling for further study of thromboprophylaxis/antiplatelet practices in this setting. Second, it discloses key management patterns, notably routine discontinuation of cytoreduction, which had a detrimental impact on outcomes. Third, correlation of uncontrolled platelets and overzealous hematocrit control with higher complication rates in ET and PV, respectively, underscores importance of judicious target control. Further, CALR driver mutation status associated with bleeding risk in ET, independent of platelet count, suggesting additional contributing mechanisms. Finally, ruxolitinib use was an independent predictor of perioperative complications in MF, though this may reflect skewing towards higher-risk populations. Further studies will be required to validate findings, with this data serving as a preliminary signal for awareness of risk and reappraisal of management strategies.

A Globally Applicable “Triple AAA” Risk Model for Essential Thrombocythemia Based on Age, Absolute Neutrophil Count, and Absolute Lymphocyte Count

▪BackgroundThe detrimental effect of leukocytosis on survival in myeloproliferative neoplasms (MPN) has been well established for primary myelofibrosis (PMF), polycythemia vera (PV) and essential thrombocythemia (ET ) (JCO. 2018;36:310; BJH. 2020;189:291) Previous studies have also implicated leukocytosis as a risk factor for leukemic transformation (Mayo Clin Proc. 2017;92:1118) and thrombosis in MPN (Blood Adv. 2019;3:1729). However, it is currently not clear as to which component(s) of white blood cells is responsible for these observations. In the current study, we sought to examine the individual prognostic contribution of absolute neutrophil (ANC), lymphocyte (ALC) and monocyte (AMC) counts, on overall (OS), leukemia-free (LFS), and myelofibrosis-free (MFFS) survival and in ET.MethodsStudy patients (n=349) were retrospectively recruited from the Mayo Clinic MPN database of 1,249 WHO-defined ET patients, evaluated over five decades (1967-2021), based on availability of information on ANC, ALC and AMC. Conventional criteria were used for diagnosis and definitions of major complications, including leukemic or fibrotic transformation (Blood 2016;127:2391). Conventional statistical methods were applied using JMP Pro 14.0.0 software package, SAS Institute, Cary, NC. Multivariable analyses included previously established risk factors for survival.Results349 patients (median age 57 years, range 18-89; females 61%) with ET were included in the study: 46% JAK2, 34% CALR, 16% triple-negative and 4% MPL mutated; IPSET risk category high 24%, intermediate 41%, and low 35%; presenting median (range) values were 13.8 g/dL (11.1-16.4) for hemoglobin, 8.2 x 10(9)/L (3.2-52) for leukocyte count, and 859 x 10(9)/L (451-3460) for platelet count; palpable splenomegaly was present in 48 (14%); median followup was 10 years (range 0-47), during which time 118 deaths, 52 fibrotic progressions, and 14 leukemic transformations were documented.Multivariable analysis identified older age (p<0.001), increased ANC (p<0.001), decreased ALC (p=0.03), and male sex (p=0.04), but not AMC (p=0.8), venous thrombosis (p=0.4), or arterial thrombosis (p=0.4), as independent risk factors for OS. ANC of ≥8 x 10(9)/L and ALC of <1.8 x 10(9)/L were determined as appropriate cut-off values by ROC analysis. Subsequent multivariable analysis using these cut-off values resulted in HR (95% CI) of 5.2 (3.4-7.9; p<0.001) for age >60 years, 3.1 (2.1-4.6; p<0.001) for ANC, and 2.0 (1.4-3.0; p<0.001) for ALC; male sex was no longer significant in this analysis (p=0.14). An operational HR-based risk score assigned 3 adverse risk points for older age (>60 years), 2 for increased ANC (≥8 x 10(9)/L) and 1 for ALC (<1.8 x 10(9)/L), resulting in an new Age Anc Alc (AAA; triple A) risk model for survival in ET with estimates of median survival ranging from 9.7 to 36.6 years (Figure 1). In addition, ALC <1.8 x 10(9)/L was associated with inferior LFS (p=0.06) and MFFS (p=0.07) while AMC as a continuous variable showed borderline significance for MFFS (p=0.18). In univariate analysis, JAK2V617F allele burden showed significant association with OS (p=0.02), LFS (p=0.05) and MFFS (p=0.001); however significance for OS was lost in mutivariable analysis that included ANC and ALC.An external validation cohort from the University of Florence (n=485) confirmed the independent survival risk contribution from age >60 years (p<0.001; HR 9.9, 95% CI 5.4-18.0), ANC ≥8 x 10(9)/L (p=0.02; 1.9, 1.1-3.5) and ALC <1.8 x 10(9)/L (p<0.001; 2.0, 1.3-3.0). The Triple A risk model was also effectively applied on the Florence validation cohort (Figure 1): median follow-up 8.4 years; 87 deaths; 43 fibrotic progression; 12 leukemic transformations. The association of ALC <1.8 x 10(9)/L (p=0.04) and AMC (p=0.002) with fibrotic transformation was also validated in the Florence cohort.Conclusions:The current study identifies increased ANC and decreased ALC as age-independent risk factors for survival in ET, thus allowing the development of a globally applicable simple to use “Triple A” risk model that is based on Age, ANC and ALC. Decreased ALC also predicted fibrotic and leukemic progression. Our observations suggest potential value for immune profiling as an additional prognostic tool in MPN. [Display omitted] DisclosuresSzuber: Novartis: Honoraria. Vannucchi: BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees.

Assessing Bone Marrow Activity in Patients with Essential Thrombocythemia and Prefibrotic Myelofibrosis: Results of a Pilot Study of [18F]FLT PET

▪BackgroundAmong several groups of clinicians and hematopathologists a conflict of opinion has been repeatedly expressed concerning the validity of bone marrow (BM) features characterizing myeloproliferative neoplasms (MPNs). In this regard, controversy is mainly focused on the distinction between essential thrombocythemia (ET) and pre-fibrotic/early primary myelofibrosis (pre-PMF) Although other groups confirmed the characteristic BM features and emphasized the clinical impact to discriminate both MPN subtypes the existence of pre-PMF has been questioned, including clinical usefulness and particularly reproducibility of the corresponding diagnostic guidelines. In this context, it has been criticized that the MPN classification proposed by the World Health Organization (WHO), updated in 2008 and revised in 2016,was focused on BM morphology as the gold standard of diagnosis.The current standard for follow-up of these patients is based on pathological markers (peripheral blood counts and/ bone marrow histomorphology) and molecular markers. Bone marrow examination is the gold standard method to assess the disease's extent; it offers detailed information about cellularity, the morphology of each lineage, the degree of fibrosis, and the transformation and dysplastic features. However, many patients are reluctant to go for this invasive technique which precludes precise disease activity assessment at the desirable frequencies. A non-invasive technique that can offer reliable prognostic and predictive information about the disease is lacking.The objective of this study is to explore the diagnostic value of FLT-PET in malignant hematopoiesis of Pre-PMF and ET. The potential to use FLT-PET metrics to differentiate between Pre-PMF and ET is assessedMethodsA total of 13 patients (mean age of 43.23 ± 14.42 years, 7 males and 6 females) with Essential Thrombocythemia (ET) and/or Prefibrotic myelofibrosis were included in this study. One male subject was excluded due to an inconclusive diagnosis. The study was approved by the institutional review board. Written informed consents were obtained from all subjects. Each subject underwent FLT PET imaging as well as bone marrow examination (gold standard) and all were tested for JAK2v617F , CALR and MPL . Semi-quantitative (SUVmax and SUVmean) measurements of FLT uptake in the liver, spleen and Lumbar spine, SUVmean, as well as the Total Lesion Glycolysis (TLG) of the Lspine were performed. Results from the two patient cohorts were compared using = Kruskal-Wallis statistical test. A P-value of <0.05 is considered to be statistically significant.Discussion:Pre‐PMF and ET exhibited different features of bone marrow; however, this is not always easy to judge objectively, making pathologists' distinction often suboptimal. And in another scenario, bone marrow which is mandated for diagnosis, cannot be obtained due to technical issues or patient-related factors. In the 2016 revised classification,pre-PMF was recognized as a separate entity, distinct from ET. Thrombosis and hemorrhage represent two of the main causes of morbidity and mortality in patients with ET. Incidence of arterial and venous thrombosis prior to diagnosis revealed no significant differences (23% /20 and 9/8%) in WHO-defined ET compared with pre-PMF; thrombotic complications were also similar during the follow-thrombosis is not significantly different, whereas bleeding is more frequent in pre-PMF.From clinical prespective it is important to differentiate between the two categories.ResultsThe differences in FLT SUVmax and SUVmean measurements in the three organs (liver, spleen, and LSpine) between the ET and Pre-PMF patients were not statistically significant (P>0.05). In contrast, TLG measurements in the LSpine were statistically different (P=0.013), and therefore, compared to gold standard bone marrow results, TLG can separate ET and Pre-PMF patients.ConclusionTLG of the Lumbar Spine in FLT PET images is a potential quantitative parameter to discriminate between ET and PRE-PMF patients [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

The 1.5 Million Platelet Count Threshold in Essential Thrombocythemia: Phenotype and Genotype Correlates and Relevance to Vascular Events

▪BackgroundCurrent NCCN and ELN guidelines lack supporting evidence in regards to initiation of cytoreductive therapy in essential thrombocythemia (ET) with extreme thrombocytosis (ExT) ≥1500 x 10 9/L (NCCN guidelines: myeloproliferative neoplasms, version 2. 2019, Barbui, Leukemia, 2018).; we sought to determine prevalence and establish phenotype and genotype correlates for ET with ExT and assess its impact on thrombotic and bleeding events, in the context of aspirin therapy or cytoreduction.Methods1,249 WHO-defined ET patients evaluated over five decades (1967-2021) were retrospectively recruited from the Mayo Clinic. Conventional criteria were used to define major arterial and venous thrombosis and major hemorrhage. Conventional statistical methods were applied using JMP Pro 14.0.0 software package, SAS Institute, Cary, NC.Results 1.i) Phenotype and genotype correlatesAmong 1,249 consecutive patients with ET, 104 (8%) displayed Ext ≥1500 x 10 9/L, at time of initial diagnosis; these patients were characterized by younger age (median 47 vs 59 years; p<0.001) female gender (80% vs 62%; p<0.001), CALR mutation (39% vs 25%; p=0.004), lower hemoglobin (median 13.1 vs 13.7 g/dl; p<0.0001), leukocytosis ≥11 x 10 9/l (42% vs 23%; p<0.0001), and palpable splenomegaly (22% vs 14%; 0.03); multivariable analysis confirmed associations with age, anemia, leukocytosis, and CALR mutation. Acquired von Willebrand syndrome was reported in 4/9 (44%) vs 27/78 (35%) tested patients, with or without Ext ≥1500 x 10 9/L, respectively (p=0.57); however, comparison using platelet ≥1000 x 10 9/L resulted in near-signficant difference (46% vs 29%; p=0.11). NGS was performed in 297 patients and showed a non-sigificant association with U2AF1 mutations (5% vs 0.4%; p=0.11). ExT ≥1500 x 10 9/L was present in 25/986 (3%), 42/891 (5%), and 15/558 (3%) in the validation cohort; the limited number of cases precluded comparative analyses. 1.ii )Correlation with vascular events at/prior to diagnosisArterial or venous thrombosis at/prior to diagnosis occurred in 190 (15%) and 111 (9%) patients, respectively, and major hemorrage in 50 (4%). Ext ≥1500 x 10 9/L was associated with major hemorrhage (HR 2.9; 1.3-6.3), but not with arterial (p=0.15) or venous (p=0.41) thrombotic events, at/prior to diagnosis. Instead, multivariable analysis for events at/prior to diagnosis identified male gender (p=0.02), JAK2 mutation (p=0.01), and cardiovascular risk factors (p=0.001) as risk factors for arterial thrombosis and JAK2 mutation (HR 2.8; 1.4-5.7) as a risk factor for venous thrombosis.iii )Correlation with vascular events after diagnosisAt median follow-up of 10 years, arterial or venous thrombosis occurred in 222 (18%) and 97 (8%) patients, respectively, and major hemorrage in 128 (11%). Ext ≥1500 x 10 9/L at diagnosis was not associated with arterial (p=0.35) or venous (p=0.23) thrombosis-free survival or hemorrhage-free survival (p=0.24). Instead, multivariable analysis identified age >60 years, presence of cardiovascular risk factors, and history of arterial thrombosis, as risk factors for arterial thrombosis-free survival; and male gender and history of venous thrombosis as risk factors for venous thrombosis-free survival; and age >60 years and leukocytosis of ≥11 x 10 9/L as risk factors for hemorrhage-free survival. In addition, aspirin therapy was idependently protective of venous thrombosis (HR 0.5; 0.2-0.9), and also of arterial thrombosis, in univariate analysis (HR 0.6; 0.3-0.9), without being associated with an increased risk of major hemorrhage (p=0.64); by contrast, beneficial effect from cytoreductive therapy was not evident for either arterial (p=0.37) or venous (p=0.77) thrombosis. In low-risk patients with Ext ≥1500 x 10 9/L, both aspirin and cytoreductive therapy were protective of venous events (Figure 1), without affecting hemorrhage-free survival.ConclusionExT ≥1500 x 10 9/L in ET was associated with major hemorrhage at diagnosis but did not affect thrombosis-free or hemorrhage-free survival. Initial therapy with aspirin and/or cytoreductive therapy was protective of venous events in ET patients with ExT ≥1500 x 10 9/L, including those with low-risk disease, without enhancing the risk of hemorrhage. The limited number of informative cases with ExT in the validation cohort, underscore the foreseeable challenges associated with controlled studies. [Display omitted] DisclosuresSzuber: Novartis: Honoraria. Vannucchi: AbbVie: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Barbui: AOP Orphan: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Clinical and molecular predictors of fibrotic progression in essential thrombocythemia: A multicenter study involving 1607 patients.

The current retrospective study involving a total of 1607 patients was designed to identify clinical and molecular variables that were predictive of inferior myelofibrosis‐free survival (MFS) in WHO‐defined essential thrombocythemia (ET), utilizing three independent patient cohorts: University of Florence, Italy (n = 718); Mayo Clinic, USA (n = 479) and Policlinico Gemelli, Catholic University, Rome, Italy (n = 410). The Florence patient cohort was first examined to identify independent risk factors for MFS, which included age > 60 years (HR 2.5, 95% CI 1.3–4.9), male sex (2.1, 1.2–3.9), palpable splenomegaly (2.1, 1.2–3.9), CALR 1/1‐like or MPL mutation (3.4, 1.9–6.1) and JAK2V617F variant allele frequency > 35% (4.2, 1.6–10.8). Subsequently, an operational molecular risk category was developed and validated in the other two cohorts from Mayo Clinic and Rome: “high molecular risk” category included patients with JAK2V617F VAF >35%, CALR type 1/1‐like or MPL mutations; all other driver mutation profiles were assigned to “low molecular risk” category. The former, compared to the latter molecular risk category, displayed significantly higher risk of fibrotic transformation: Florence cohort with respective fibrotic transformation risk rates of 8% vs. 1.2% at 10 years and 33% vs. 8% at 20 years (p < 0.001; HR 6.1; 95% CI 3.2–11.7); Mayo Cohort, 16% vs. 7% at 10 years and 44% vs. 25% at 20 years (p < 0.001; HR 2.5; 95% CI 1.6–4.1); and Rome cohort 7.8% vs. 4.6% at 10 years and 31.2% vs. 7.1% at 20 years (p = 0.007, HR 2.7; 95% CI 1.3–5.8). The present study provides practically useful risk signals for fibrotic transformation in ET and facilitates identification of patients who require close monitoring and appropriate counseling.

Essential Thrombocythemia Versus Pre-Fibrotic/Early Primary Myelofibrosis: Discrimination By Laboratory and Clinical Data

In clinical practice there is an active interest to evaluate whether laboratory or clinical parameters would help to distinguish WHO-defined essential thrombocythemia (ET) and pre-fibrotic / early primary myelofibrosis (pre-PMF) in patients presenting with thrombocytosis given the very different outcome and treatment options.A first step in this direction was initiated by Carobbio et al. (Am J Hematol.2012;87:203-204), who used hemoglobin (Hb) level, white blood cell (WBC) count and serum lactate dehydrogenase (LDH) level in a dichotomized fashion, resulting in a step-by-step algorithm (the so-called Bergamo algorithm).The aim of the present study was to extend and improve this algorithm. In addition to the laboratory parameters, leftshift in the peripheral blood cell count (presence of single erythroblasts or myelocytes, metamyelocytes, promyelocytes or myeloblasts) and splenomegaly were also tested as presumptive parameters. The second, more important approach was to look not necessarily at each parameter in a stepwise order, but to develop a logistic regression model.Only patients diagnosed with ET or pre-PMF according to the 2008 WHO diagnostic criteria with a complete dataset (age at diagnosis, complete blood counts, left-shift, LDH-levels and presence of splenomegaly), consistent diagnosis between bone marrow (BM) morphology and clinical findings, platelet count greater than 450 x 109/L and no evidence for masked/early stages of polycythemia vera were eligible for this study. These criteria were met by 359 patients who were included in the study.Results from the first application of the Bergamo algorithm on our cohort are given in Table 1. The expanded algorithm, which includes leftshift and splenomegaly increased sensitivity with regard to pre-PMF and the number of undetermined cases could be reduced to 93 (Table 1).In an alternative approach, a logistic regression model was used, which weights the information contained in the laboratory parameters and in the dichotomous variable splenomegaly in an optimal, data-driven way and exploits the full information of the continuous laboratory parameters, instead of dichotomizing them. Leftshift was removed from the final model due to obvious negligibility for the sake of model parsimony.While step-by-step procedures deliver a prediction in the form of a patient's direct classification into either ET or pre-PMF (or undetermined), a logistic regression model transforms each set of a patient's characteristics into a predicted probability for pre-PMF. The final model's calibration plot shows a good agreement between observed and shrunk predicted pre-PMF probabilities; accordingly, the Hosmer-Lemeshow test shows a non-significant test result (p=0.255).The predicted shrunk pre-PMF probability can be used as a prediction score ranging from 0 (ET) to 1 (pre-PMF). It is calculated using the following formula:Score = 1 / [1+exp(-21.01-0.249*Hb+0.613*log2(WBC) + 2.63*log2(LDH) +1.04*Splenomegaly)]Here, log2 denotes the binary logarithm (1 is inserted for presence of splenomegaly, zero otherwise). To transform this score into a dichotomous classification rule (ET vs. pre-PMF) a cutoff equal to 0.438 is proposed which leads to approximately equal sensitivity and specificity in our data.Utilizing only dichotomized laboratory parameters we could reproduce the results of the Bergamo algorithm yielding a sensitivity and specificity of about 50% among our study cohort. Expanding these parameters by leftshift and splenomegaly, we achieved an increase of these values and provide predictions also for previously undetermined cases. Finally, we demonstrated that a risk score formula based on statistical modeling is able to exploit the information contained in the same predictor variables in a much more efficient way (Table 1). Although, according to the WHO criteria, BM biopsy examination persists as an integral part of the final diagnosis, laboratory parameters may provide clinicians with additional information to suspect pre-PMF in a patient with a presumptive clinical diagnosis of ET. However, in this context it should be underscored that our formula and the proposed cutoff for the resulting score need to be externally validated in other large cohorts of patients presenting with thrombocythemic myeloproliferative neoplasms, and most important, in prospective clinical trials. [Display omitted] DisclosuresKrauth:Celgene: Honoraria; Novartis: Honoraria; Takeda: Honoraria; Amgen: Honoraria; BMS: Honoraria; Janssen Cilag: Honoraria; AOP Orphan Pharmaceuticals AG: Honoraria. Gisslinger:AOP Orphan Pharmaceuticals AG: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; PharmaEssentia: Consultancy, Honoraria; Janssen Cilag: Honoraria; Shire: Honoraria; Takeda: Honoraria.

MPL-Mutated Essential Thrombocythemia: A Morphologic Reappraisal

Background:Myeloproliferative leukemia virus oncogene (MPL)-mutated essential thrombocythemia (ET) is uncommon, with a cited incidence of less than 5%, while that of MPL-mutated primary myelofibrosis (PMF) is at least twice as frequent (Blood. 2006;108:3472;Blood.2008;112:141). MPL-mutated ET cohorts also have higher reported rates of fibrotic progression than their MPL wild type counterparts (Blood. 2014;124:2507). These observations suggest the possibility that some instances of MPL-mutated ET might actually represent prefibrotic PMF.Methods:Patients were recruited from institutional databases of the Mayo Clinic, Rochester, MN, USA. Diagnoses were according to the 2016 World Health Organization (WHO) criteria (Blood. 2016;127:2391). Study inclusion criteria required the availability of bone marrow biopsy slides for central review by one of the authors (C.A.H.). Central pathology review included assessment of bone marrow cellularity and extent of tri-lineage proliferation, megakaryocyte morphology and grading of reticulin fibrosis. Data was additionally collected from MPL-mutated patients with PMF, for comparison. Standard statistical methods were used for statistical analysis, including calculation of survival data (JMP® Pro 13.0.0, SAS Institute, Cary, NC, USA).Results:A total of 665 patients with ET were annotated for their driver mutational status; 18 (2.7%) were reported out as being MPL-mutated; by comparison, among 867 patients with PMF, 47 (5.4%) were signed out as MPL-mutated. Among the 18 cases with MPL-mutated ET, bone marrow slides were available for central pathology review in 14 patients (Table 1). The latter were subsequently reassigned the diagnosis of either prefibrotic PMF (n=8; 57%) or were felt to be morphologically consistent with true WHO-defined ET (n=6; 43%). Comparison of these two distinct histopathological patterns, i.e. true ET vs reassigned prefibrotic PMF, was respectively characterized by lower (median 35%, range 30-50) vs higher (median 65%, range 40-80) bone marrow cellularity (P<0.001), ET (n=6) vs PMF (n=8) consistent megakaryocyte morphology (P<0.001) and presence of tri-lineage proliferation (0% vs 100%; P<0.001); in contrast the degree of reticulin fibrosis was similar between the two (P=0.1) (Table 2).The reassigned prefibrotic PMF (n=8), vs confirmed ET (n=6), cases also displayed a higher frequency of increased serum levels of lactate dehydrogenase (60% vs 0%; P=0.02), higher likelihood of displaying hemoglobin levels below the sex-adjusted reference range values (29% vs 0%; P=0.1), leukoerythroblastosis (14% vs 0%; P=0.2), constitutional symptoms (13% vs 0%; P=0.2) and a higher incidence of thrombosis history at presentation (38% vs 0%; P=0.04) (Table 2). Interestingly, reassigned prefibrotic PMF also displayed a narrower MPL mutational spectrum compared to those confirmed as ET (MPLW515L/K incidence 100% vs 60%; P=0.04). The incidences of abnormal karyotype and high risk molecular mutations (ASXL1, SRSF2 and U2AF1) were similar between the two.We documented a higher incidence of post-diagnosis thrombosis in prefibrotic PMF (25% vs 0%; P=0.1) but similar rates of leukemic transformation (0% for both) and fibrotic progression (38% vs 33%); when all 665 ET patients were assessed for myelofibrosis-free survival, MPL-mutated cases (prior to central review) displayed significantly worse outcome, compared to patients with other driver mutations (Figure 1a). Median overall survival in confirmed MPL-mutated ET, ET re-classified as PMF, and MPL-mutated PMF was not reached, 11.6 and 5.3 years, respectively (confirmed ET vs PMF, P=0.01; ET re-classified vs PMF, P=0.04; confirmed ET vs ET re-classified as PMF, P=0.54) (Figure 1b).Conclusions:The current study suggests that the majority of routinely-assigned MPL-mutated ET probably represents prefibrotic PMF, when morphologically scrutinized. Prior to central pathology review, we show a higher rate of fibrotic progression in MPL-mutated ET, compared to patients with other driver mutations; accordingly, after central pathology review, the similar rate of fibrotic progression between morphologically confirmed MPL-mutated ET and those reassigned as prefibrotic PMF further suggests the latter to be biologically more akin to PMF, despite its ET-consistent morphologic features. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Integrative Next Generation Sequencing of Myeloproliferative Neoplasms and Correlation of Genetic Variations to Disease Severity

INTRODUCTIONMyeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell diseases characterized by the overproduction of differentiated myeloid cells. In classical BCR-ABL negative MPNs -essential thrombocythemia (ET), polycythemia vera (PV), prefibrotic primary myelofibrosis (prePMF) and overt myelofibrosis(MF) - driver mutations are described in JAK2, CALR and MPL genes. However, there is no compelling evidence to explain how each mutant gene can lead to phenotypically distinct and/or overlapping diseases, nor is it understood how additional gene aberrations modulate MPN phenotype. In an attempt to understand the molecular events that underlay clinical characteristics of MPNs, we sequenced hematopoietic cells of MPN patients with a focus on MF landscape. METHODSPatients were consented to MI-ONCOSEQ study approved by the University of Michigan IRB. MI-ONCOSEQ is a CLIA-certified Next Generation Sequencing (NGS) platform designed to identify genetic aberrations in a panel of 1,711 genes. MI-ONCOSEQ test can identify somatic point mutations, small insertions/deletions (indels), and copy number alterations by comparing the tumor sample (blood or bone marrow derived myeloid cells) to the matched normal sample (buccal swab or saliva derived normal cells). The assay also includes gene expression and gene fusion analysis of 24,774 capture targets based on transcriptome sequencing. Significant genetic variants were reported based on tumor burden in sample, as samples were collected at various stages of disease progression and treatment. Diagnoses of ET, PV, prePMF, or overt MF were confirmed by 2016 WHO classification as close to the time of sample collection as possible. RESULTSA cohort of 166 patients with suspected classical MPNs were enrolled, of which 32 were excluded from analysis due to diagnosis of other myeloid malignancy or a benign condition. Of the 134 evaluable patients, 97 (age range 33-84 yrs) were determined to have WHO-defined overt MF and 37 (age range 20-83 yrs) were determined to have WHO-defined ET, PV, or prePMF (14, 15, and 8, respectively). Most (95% of overt MF and 90% of ET/PV/prePMF) harbored driver mutations in JAK2, CALR, or MPL. In total, 167 genes were found to be mutated in 97 patients with overt MF (51 with primary MF, 46 with post-PV/ET MF) (Figure 1) as compared to only 37 genes in 37 patients with ET/PV/prePMF (Figure 2). There was a significant difference (p<0.0001) between the number of genetic variants in overt MF (4 per patient, range 0-9) as compared to ET/PV/prePMF (2 per patient, range 0-7). Of note, RAS pathway genes (NRAS, KRAS, and NF1) were found to be mutated only in overt MF (24% of cases) and not in ET/PV/prePMF. A comparison of genetic variant rate in ET to PV was also found to be significant (p<0.0007) 1 vs 3 variants per patient respectively, whereas prePMF presented a genetic variant landscape that was in between ET and PV. Both primary and post-PV/ET MF had the same average variant rate of 4 per patient. CONCLUSIONSTo our knowledge, this is the largest integrative (NGS, gene expression, and transcriptome) sequencing study in patients with MPNs to date. Our results illustrate the following: 1) MF is likely an evolutionary disease arising from ET/PV/PrePMF by accumulating mutations, 2) RAS pathway activation might play a role in the transformation of ET/PV/PrePMF to overt MF and contribute to the proliferative nature of the disease, 3) Contrary to prior reports we observed an increasing mutation rate from ET < prePMF < PV < overt MF, 4) The aggressive nature of PV might be partly explained by a higher mutation burden compared to ET, 5) PrePMF displays an intermediate number of mutations which correlates with the clinical phenotype. Gene expression analysis to determine activated pathways and multivariate analysis to correlate clinical phenotype and gene to gene relationships are in progress. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

The prognostic relevance of serum lactate dehydrogenase and mild bone marrow reticulin fibrosis in essential thrombocythemia.

The 2016 World Health Organization (WHO) diagnostic criteria for myeloproliferative neoplasms (MPN) underscore the prognostically-relevant distinction between essential thrombocythemia (ET) and prefibrotic primary myelofibrosis (pre-PMF). In addition, leukocytosis has been identified as an important prognostic marker in otherwise WHO-defined ET. However, controversy remains regarding the objectivity of morphologic criteria in distinguishing ET from pre-PMF and the precise prognostic cutoff values for leukocytosis. Serum lactate dehydrogenase (LDH) level might be a biologically more accurate measure of leukocyte turnover and a more sensitive marker of pre-PMF, in otherwise WHO-defined ET. In the current study of 183 consecutive patients with WHO-defined ET, the presence of grade 1 bone marrow (BM) fibrosis did not affect presenting clinical or laboratory features; in contrast, increased serum LDH at diagnosis was associated with leukocytosis (p = .002), thrombocytosis (p < .001), palpable splenomegaly (p = .03) and higher international prognostic score (IPSET) (p = .002); serum LDH did not correlate with BM fibrosis, JAK2/CALR/MPL or TET2/ASXL1 mutations. In univariate analysis, risk factors for survival included age ≥60 years (p = .002; HR 10.2, 95% CI 2.3-44.6), male sex (p = .02; HR 3.2, 95% CI 1.2-8.2), leukocyte count ≥15 × 109 /L (p = .007; HR 4.7, 95% CI 1.5-14.6), and increased serum LDH (p = .002; HR 3.7, 95% CI 1.5-9.1), but not BM fibrosis (p = .17). In multivariable analysis, age, sex and serum LDH remained significant; serum LDH also remained significant, in the context of IPSET (p = .003) and in patients with leukocytosis (p = .003). We conclude that serum LDH level carries an independent prognostic value for survival in ET and might represent a biologically more accurate surrogate for leukocytosis.

Impact of High Molecular Risk Mutations on Overall Survival in WHO-Defined Essential Thrombocythemia and Prefibrotic Primary Myelofibrosis

We investigated a cohort of 200 patients diagnosed with essential thrombocythemia (ET, N=115) or prefibrotic primary myelofibrosis (prePMF, N=85). All diagnoses were performed by strictly adhering to the 2016 WHO criteria. Investigations into the molecular genetic markup of these patients were performed using next generation sequencing methods for the main genes involved in myeloproliferative neoplasms, JAK2, CALR and MPL. Additionally, four more genes considered as the most commonly mutations associated with an elevated risk for early death or leukemic transformation in PMF, comprising of ASXL1, EZH1, IDH1/2 and SRSF2 were analyzed.The median age at diagnosis in the cohort was 58,8 years, 56,4 years for ET patients and 60,7 years for prePMF patients. Median observation time was 8 years, 8,5 years in the ET group and 7,4 years in the prePMF group. 120 (60%) patients were JAK2V617F positive, 75 (65,2%) ET and 45 (52,9%) prePMF. 54 (27%) patients showed CALR positivity, 21 (18,3%) ET and 33 (38,8%) prePMF. Only a few patients were MPL positive, 8 (4%) in the whole cohort, 4 (3,5%9 ET and 4 (4,7%) prePMF. Triple negative patients, showing none of the above three mutations were 18 (9%), 15 ET (13%) and 3 prePMF (3,5%).We investigated, whether the presence or number of high molecular risk mutations between the two diagnostic groups had an effect on overall survival. Each group was divided into two categories: patients with no high molecular risk mutation and patients with one or more high molecular risk mutations. Among the ET patients, 86 (74,8%) showed no such mutation, whereas 29 (25,2%) had one or more. In the prePMF group, 73 (85,9%) displayed no mutation and 12 (14,1%) having one or more. The difference between ET and prePMF regarding the number of high molecular risk mutations was not statistically significant (p=0,075678).Additionally, we examined the difference within each diagnostic group (Figure 1). Here, we divided each portion of the cohort into three categories: patients with no high molecular risk mutation, patients with one high molecular risk mutation and patients with two or more high molecular risk mutations. Of the 29 ET patients with one or more high molecular risk mutations, 7 had two or more, of the 12 prePMF patients 4 respectively.Comparing the overall survival between ET and prePMF patients, a clear significant difference favoring ET patients could be observed (Figure 2A). No significant difference regarding overall survival was detected between patients with or without one or more high molecular risk mutations (Figure 2B). Looking at differences in overall survival within each diagnostic group with regards to the number of high molecular risk mutations, neither in the ET nor in the prePMF cohort a significant difference could be found (Figure 2C, D).In conclusion, our investigation shows that the most common high molecular risk mutations have no significant impact on overall survival in WHO-defined ET and prePMF patients. [Display omitted] [Display omitted] DisclosuresGisslinger:AOP Orphan: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Baxalta: Consultancy, Honoraria. Thiele:Novartis: Consultancy, Honoraria; Incyte Corporation: Consultancy, Honoraria. Kralovics:Qiagen: Membership on an entity's Board of Directors or advisory committees; AOP Orphan: Research Funding.

The Prognostic Relevance of Serum Lactate Dehydrogenase and Mild Reticulin Fibrosis in Essential Thrombocythemia

BackgroundThe International Working Group for Myeloproliferative Neoplasms (MPN) Research and Treatment (IWG-MRT) previously published on 1104 patients with "essential thrombocythemia (ET)" and identified 180 (16%) misdiagnosed cases with early/prefibrotic primary myelofibrosis (PMF); the latter diagnosis was associated with inferior overall (OS), leukemia-free (LFS) and myelofibrosis-free (MFFS) survival (J Clin Oncol. 2011; 29:3179). Among the 891 patients with "true" World Health Organization (WHO)-defined ET, risk factors for OS included age ≥60 years, leukocyte count ≥11 x 10(9)/L and history of thrombosis (Blood2012120:1197). In the current study, we explored the possibility that increased serum lactate dehydrogenase (LDH) level or mild grade-1 reticulin fibrosis might identify occult cases of early/prefibrotic PMF in otherwise WHO-defined ET and contribute to disease prognostication.MethodsStudy patients were selected from the Mayo Clinic institutional database of MPN based on their meeting the 2008 WHO criteria for diagnosis of ET (Blood. 2009;114:937). The degree of bone marrow (BM) reticulin fibrosis was based on "real life" BM reports from Mayo Clinic hematopathologists and often in accordance with the European consensus scoring system (Haematologica 2005;90:1128). Serum LDH levels were obtained at time of diagnosis or within 12 months of diagnosis, in the absence of any treatment. Information on the two most frequent non-driver mutations seen in ET (i.e. TET2 and ASXL1) was available in a subset of the patients (Blood 2015 126:354). Statistical analyses considered clinical and laboratory parameters obtained at time of diagnosisResultsPatient characteristics:183 patients (57% females) were evaluable for BM reticulin grading; median (range) levels were for age 59 years (15-88), hemoglobin 14 g/dL (9.1-17.1), platelets 812 x 10(9)/L (454-3300) and leukocyte count 8.5 x 10(9)/L (3.1-31.5). Palpable splenomegaly was reported in 27 (15%) patients and 12% displayed leukoerythroblastosis (LES). Driver mutational status was JAK2 in 72%, CALR 17%, MPL 2% and triple-negative in 9%. Thrombosis history at diagnosis was obtained from 13% of the patients and 12% experienced the same post diagnosis. Risk stratification according to the International Prognostic Scoring System for ET (IPSET) was 19% high, 43% intermediate and 38% low (Blood2012120:1197). BM reticulin fibrosis was graded "0" in 113 (62%) patients and "1" in 70 (38%). Serum LDH information was available in 110 patients (median194 U/L; range 135-669) and was increased in 31 (28%) patients. Mutational status for TET2 and ASXL1was available in 76 patients with mutational frequencies of 8% each.Clinical and laboratory correlates for mild reticulin fibrosis and serum LDH:We found no significant correlation between mild reticulin fibrosis (grade-1) and a number of clinical parameters, including age, sex, hemoglobin level, leukocyte count, platelet count, driver mutational status, LES, presence of palpable splenomegaly, thrombosis history or serum LDH (p=0.36). In contrast, increased serum LDH was associated with increased leukocyte count (p=0.002), increased platelet count (p<0.001), presence of palpable splenomegaly (p=0.03) and higher IPSET score (p=0.002); there were no significant correlations with age, sex, hemoglobin level, LES, thrombosis history, driver mutational status or TET2/ASXL1mutations.Survival analysis:After a median follow-up of 91 months, 42 (23%) deaths, 2 (1%) leukemic transformations, 7 (4%) fibrotic progressions and 22 (12%) thrombotic events were documented. In univariate analysis, risk factors for OS included age ≥60 years (p=0.002; HR 10.2, 95% CI 2.3-44.6), male sex (p=0.02; HR 3.2, 95% CI 1.2-8.2), leukocyte count ≥15 x 10(9)/L (p=0.007; HR 4.7, 95% CI 1.5-14.6), and increased serum LDH (p=0.004; HR 3.7, 95% CI 1.5-9.1), but not BM reticulin fibrosis (p=0.17). In multivariable analysis, age, sex and LDH remained significant; serum LDH also remained significant for OS, in the context of IPSET, whereas it did not appear to influence thrombosis-free survival (p=0.58), LFS (p=0.84) or MFFS (p=0.34).ConclusionsThe current study suggests that serum LDH might supersede leukocyte count as an independent risk factor for overall survival in ET; in contrast, mild reticulin fibrosis was irrelevant in terms of both prognostic value and disease phenotype. DisclosuresNo relevant conflicts of interest to declare.

Prefibrotic Primary Myelofibrosis As an Entity Distinct from Other Philadelphia-Chromosome Negative Myeloproliferative Neoplasms - Data from the Austrian Reclassification Project

Introduction:The distinction between essentialthrombocythemia(ET) and early, prefibrotic primary myelofibrosis (prePMF) by strictly applying the criteria of the WHO classification results in a newly defined subgroup of myeloproliferative neoplasm (MPN) in which the frequency and severity of clinical features are currently poorly characterized.Since prePMF was usually summarized under the subgroup of ET in previous classifications, little is known about the frequency of prePMFamong MPN. The importance of accurate diagnosis, however, is underlined by various publications that could demonstrate a significant impact on management and outcome of these patients.Aims:The aim of this study was to describe the clinical characteristics and symptoms at diagnosis of prePMF as a distinct entity and to evaluate the course of the disease in regard to survival, transformation into overt myelofibrosis and acute leukemia.Methods:All patients with representative bone marrow biopsies at presentation and complete clinical data at time of diagnosis and follow up were included in this study. All patients included were recruited from the MPN cohort of the Medical University of Vienna.Results:In total, 807 MPN patients diagnosed according to the WHO 2008 criteria were analyzed. The relative frequency of prePMF in our cohort was 17.6% (n=142) as opposed to 27.4% (221) in ET (Fig. 1). The median age for prePMF patients was 63.4 years (range 26.9-88.1) and 55.1% were female. The majority showed an elevated platelet count (median 770 G/l, range 78-2869), hemoglobin levels were on the lower end of the normal range in both genders (median 13.9, range 8.1-18.4 and 13.2, range 7.9-16.2 in men and women respectively). Leukocyte counts in the upper range of normal were common (median 9.87, range 4.0-46.0). The lactate dehydrogenase levels (LDH) were markedly elevated (median 303, range 153-729 with an institutional cut-off of 250 U/L). Therewasalso a considerate proportion of patients with splenomegaly (39.8%). Further, 22.6% of patients reported constitutional symptoms such as night sweats and weight loss. Fiber grade of 1 of a three-graded score in the bone marrow biopsy was reported in 26.2% of cases. 27.0% of patients presented withleftshiftingwith a few peripheral blasts. JAK2 positivity was found in 57.1%, CALR in 32.7 and MPL in 3.3% of cases. Only 5.9% were triple negative. 5-, 10- and 20-year survival rates were 87.6%, 67.0% and 28.8% respectively (38.2% of patients followed to death). Cumulative rate of progression into overt fibrosis was 34.2% after 10 and 58.8% after 20 years (Fig. 2).Discussion:Our data highlight important features of prePMF. Firstly, compared to ET, it has a later onset. More importantly, thrombocytosis is not a feature limited to ET, but is also frequently seen in prePMF and is therefore not suitable to accurately characterize MPN at time of diagnosis. However, leukocytosis and elevated LDH levels are features uncommon for ET as is fiber grade > 0 that is almost never seen in the WHO-defined ET, but relatively common in prePMF. Splenomegaly and presence of a few blasts are generally signs of beginningextramedullaryhematopoiesis are therefore more commonly associated with early stages primary myelofibrosis. Lastly, overall survival and fibrosis-free survival is substantially impaired in prePMF in comparison to data previously published for ET and similar to polycythemiavera.In conclusion, prePMF is a distinct entity, that while sharing some features of ET, most notably thrombocytosis, shows several striking features that should be regarded when investigating newly diagnosed MPN patients. [Display omitted] [Display omitted] DisclosuresGisslinger:Baxalta: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; AOP Orphan: Consultancy, Honoraria.

Myeloproliferative neoplasms: Morphology and clinical practice.

In myeloproliferative neoplasms (MPNs), controversy persists regarding the usefulness and reproducibility of bone marrow (BM) features. Disagreements concerning the WHO classification are mainly focused on the discrimination between essential thrombocythemia (ET) and prefibrotic/early primary myelofibrosis (prePMF) and prodromal polycythemia vera (PV). Criticism mostly refers to lack of standardization of distinctive BM features precluding correct morphological pattern recognition. The distinction between WHO-defined ET and prePMF is not trivial because outcome is significantly worse in prePMF. Morphology was generally considered to be non-specific for the diagnosis of PV. Recent studies have revealed under-diagnosis of morphologically and biologically consistent PV.

Spleen enlargement is a risk factor for thrombosis in essential thrombocythemia: Evaluation on 1,297 patients.

Spleen enlargement, present in 10-20% of Essential Thrombocythemia (ET) patients at diagnosis, is a feature clinically easy to assess, confirmable by echography with a very low chance of misinterpretation. Nonetheless, the clinical and prognostic role of splenomegaly has been seldom evaluated. From 1979 to 2013, 1297 ET patients retrospectively collected in the database of the Lazio Cooperative Group and Bologna University Hospital were evaluable for spleen enlargement at diagnosis and included in the analysis. On the whole, spleen was enlarged in 172/1297 (13.0%) patients; in most cases (94.8%) splenomegaly was mild (≤5 cm). Patients with splenomegaly were younger, predominantly male, presented higher platelet count and JAK2V617F allele burden and had a lower incidence of concomitant cardiovascular risk factors. At least one thrombotic event during follow-up occurred in 97/1,125 (8.6%) patients without spleen enlargement compared to 27/172 (15.7%) patients with spleen enlargement (P = 0.003). Despite comparable use of cytoreductive/antiplatelet therapies in the two groups, the cumulative risk of thrombosis at 5 years was significantly higher in patients with baseline splenomegaly (9.8% versus 4.4% in patients without splenomegaly, P = 0.012). In multivariate analysis exploring risk factors for thrombosis, splenomegaly retained its negative prognostic role, together with previous thrombosis, leucocyte count and male gender. Baseline splenomegaly seems to be an independent additional risk factor for thrombosis in nonstrictly WHO-defined ET patients. This data could be useful in the real-life clinical management of these patients.

JAK2V617F-Positive Patients with Essential Thrombocythemia or Early Primary Myelofibrosis: The Impact of Histological Diagnosis on Outcome

IntroductionIt is acknowledged that an accurate histological diagnosis may distinguish Essential Thrombocythemia (ET) from early Primary Myelofibrosis (early-PMF), which is projected to worse outcome in terms of survival and disease evolution into acute leukemia (AL) or overt myelofibrosis (MF). It is also accepted that the outcome of ET is related to the mutational status, with JAK2V617F mutation having a negative impact. In previous analyses, outcome data derived from the admixture of the two variables, histology and mutational status. Here, we present a large cohort of ET/early-PMF patients positive for the JAK2V617F mutation, with the aim to evaluate the impact on outcome of the sole histological definition.MethodsA clinic-pathologic database of ET patients followed in four Italian Hematology Centers was created and a total of 475 WHO-diagnosed ET or early-PMF JAK2V617F-positive patients was collected. Bone marrow specimens were performed or reviewed at local institution. Baseline clinical/molecular characteristics and outcome measures (vascular complications, disease transformation/progression, overall and event-free survival) were evaluated. In all patients, JAK2V617F allele-burden was assessed in granulocyte DNA by using ipsogen JAK2 MutaQuant Kit (qPCR). The study was approved by the Ethic Committee of each participating Centers.ResultsOverall, 329 WHO-defined ET and 146 early-PMF patients positive for the JAK2V617F mutation were included in the study. Median follow-up was 6.6 years (range: 0.5-32.4). Compared to ET patients, early-PMF patients presented with older age (median, 57 versus 53.5yr, p=0.02), lower hemoglobin levels (median, 14.2 versus 14.5 g/dl, p=0.01), higher leukocyte count (median, 10.4 versus 9.5x109/l, p=0.01), and higher incidence of spleen enlargement (35.9% versus 13.9%, p<0.001). JAK2V617F mutation was heterozygous in 90% and 87% of ET and early-PMF patients, respectively (p=0.34). Use of antiplatelet and cytoreductive therapies was also comparable in the two groups. During follow-up, 32 (9.7%) ET and 18 (12.3%) early-PMF patients experienced a total of 59 thrombotic events (arterial: 49%), with an incidence rate of 1,3% patients/yr. The cumulative incidence of thrombosis was 8% and 14% at 5 and 10 years, respectively. Overall, 27 patients (5,6%) and 6 (1.2%) patients evolved to MF and AL, respectively. The cumulative incidence of disease progression into MF/AL was 2% and 5% at 5 and 10 years, respectively. At last contact, 28 (5.8%) patients had died, at a median age of 77.5 years (20-88), for an overall survival of 93.8% at 10 years. In early-PMF compared to ET, the 10-year survival rates (91.6% and 95%, respectively, p=0.75), leukemic transformation rates (6% and 1.2%, respectively, p=0.45) and rates of thrombosis (6.7% and 2.2%, p=0.12) were comparable. However, progression to overt MF at 5 years (4.4% and 0.9%, respectively) and 10 years (11.5% and 1.5%) was significantly worse (p=0.004). Multivariable analysis confirmed this finding and also identified homozygosity for the JAK2V617F mutation (p=0.008) as additional risk factor for disease evolution into secondary MF.The rate of composite outcomes (thrombosis, evolution into overt MF or AL and death) was significantly higher in early-PMF (3.1% vs 2,3% pts/yr) with a combined event-free survival of 69% versus 82% in ET patients at 10 yrs (figure 1).Conclusions. This study eliminates the confounding factor of different molecular status on outcome by focusing on a large cohort of WHO-defined ET/early-PMF patients, all carrying the JAK2V617F mutation. Overall, the study validates the clinical relevance of strict adherence to WHO criteria on prognosis, and particularly on disease progression into secondary MF. [Display omitted] DisclosuresPalumbo:Novartis: Honoraria, Other: Advisory Board. Martinelli:MSD: Consultancy; BMS: Speakers Bureau; Roche: Consultancy; ARIAD: Consultancy; Novartis: Speakers Bureau; Pfizer: Consultancy.

Clinical Impact of Bone Marrow Morphology for the Diagnosis of Essential Thrombocythemia: Comparison Between the British Standards (BCSH) and the WHO Criteria

Background Accurate diagnosis of essential thrombocythemia (ET) continues to be a challenging issue for both hematopathologists and clinicians. Diagnosis is usually performed by applying either the 2014 British Committee for Standards in Haematology (BCSH) guidelines or the 2008 World Health Organization (WHO) criteria. While the WHO classification requires bone marrow morphology (BM) as a major criterion, the BCSH guidelines allow diagnosis also based solely on clinical symptoms and is more focused on exclusion of the other subtypes of myeloproliferative neoplasia (MPN). However, prefibrotic/early stages of primary myelofibrosis (prePMF) may also present with thrombocytosis, while failing to meet the diagnostic signs and symptoms characterizing overt PMF. Moreover, a small fraction of polycythemia vera (PV) patients may present with low hemoglobin and hematocrit levels, but a platelet count in keeping with BCSH- and WHO-defined ET, thus mimicking phenotypically ET at onset (masked PV). Clinical outcome in prePMF patients is considerably worse than in ET patients, while treatment strategies are likely to change for prePMF patients with the use of interferon-alpha or JAK1/2-inhibitors.Aims The aim of this study was to investigate the prognostic relevance of BM morphology for ET diagnosis as underscored by the WHO classification versus the first set of the BCSH criteria that do not include BM evaluation.Methods A clinic-pathological database including 450 MPN patients was created by clinicians and hematopathologists from a major Austrian center. Treatment-naive BM biopsies were centrally re-reviewed by three of the authors, who were completely blinded to initial data (except for age and gender). Follow-up data, including clinical course and mutation status, were analyzed after the completion of the histopathology review. For purpose of this study we selected two cohorts of ET patients presenting with a sustained platelet count > 450x10^9/L: (1) 209 ET patients in accordance with the diagnostic requirements of the BCSH (A1-A3) that included no BM biopsy examination. (2) 152 patients in strict agreement with the diagnostic guidelines of the WHO including BM biopsy evaluation as major criterion. Both cohorts were compared and analyzed to regarding their presenting clinico-pathological data, driver mutation status, and follow-up. Diagnosis of post-ET myelofibrosis or progression into overt myelofibrosis with myeloid metaplasia was made according to previously published criteria.Results Following the BCSH criteria, 209 patients were diagnosed as ET. When reclassifying those cases according to the WHO criteria including BM morphology examination, 80 (38.3%) patients were diagnosed as prePMF and 14 (6.7%) as PV and two were diagnosed as PMF (0.9%). Comparison of clinical features of BCSH-ET and WHO-ET revealed significant differences in LDH levels and palpable splenomegaly at diagnosis. Fibrosis-free survival was significantly shorter in BCSH-ETs (Fig. 1A) as was overall survival (Fig. 1B). When reclassifying the BCSH cohort according to WHO criteria, progression-free and overall survival were significantly shorter in WHO-confirmed prePMF (Fig. 1C and 1D).Summary/Conclusion The striking differences in outcome are certainly linked with the entry of many prePMF cases in the BCSH-confirmed cohort. The inclusion of these cases, as well as cases with masked PV demonstrates, that BCSH criteria A1-3 may lead clinicians to refrain from performing BM biopsy in patients with elevated thrombocyte counts, which impairs accurate diagnosis with subsequent inadequate management and inferior prognosis. Our results highlight the central role of BM biopsy to achieve accurate diagnosis and differentiation of ET and prePMF. [Display omitted] DisclosuresGisslinger:Geron: Consultancy; AOP ORPHAN: Consultancy, Honoraria, Research Funding, Speakers Bureau; Sanofi Aventis: Consultancy; Novartis: Honoraria, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen Cilag: Honoraria, Speakers Bureau.

Thrombotic risk assessment in 185 WHO-defined essential thrombocythemia patients: single center experience.

Thrombosis risk in essential thrombocythemia (ET) patients can be assessed using different prognostic systems. Conventional risk factors include age more than 60 years and history of previous thrombosis. In addition, other factors such as JAK2 V617F mutations, cardiovascular risk factors, leukocytosis more than 11 × 109/l, thrombophilic factors and platelet count more than 1500 × 109/l are used in different hematology centers as high-risk features for thrombosis. Our study compared different risk model groups for thrombosis in 185 WHO-defined ET patients at the Hospital of Lithuanian University of Health Sciences Kaunas Klinikos. We found that patient distribution in low, intermediate- and high-risk groups varies using different risk stratification models. The biggest difference in risk assignment is evident in patients who are older than 60 years and have no other risk factors and in patients who are younger than 60 years but have other risk factors.This observation suggests that new prospective randomized clinical trials are needed to better stratify patients at risk for thrombosis.

Calreticulin Mutation Status Predicts Improved Disease Outcome in Prefibrotic Primary Myelofibrosis but Not in WHO-Defined Essential Thrombocythemia

The genomic landscape of myeloproliferative neoplasms (MPNs) has altered dramatically due to the recent discovery of somatic mutations of calreticulin (CALR). This discovery enables for the first time molecular information, in addition to JAK2V617F, to be used in the majority of MPN patients as an affirmative variable to discriminate MPNs from reactive myeloid proliferations. The clinical course of essential thrombocythemia (ET) or primary myelofibrosis (PMF) in patients carrying the CALR mutation was reported to be more indolent than in JAK2 positive patients and was associated with increased survival. Our aim was to investigate whether the impact of CALR expression on prognosis and clinical outcome is different in prefibrotic/early PMF (prePMF) compared to WHO-ET.In a cohort of 348 adult patients with the clinical diagnosis of either ET or PMF mutational analysis for CALR was available. Eligibility criteria for the study included: availability of mutation analysis for JAK2, MPL and CALR; availability of representative, treatment-naive bone marrow biopsy (BM); availability of a histological and clinical consensus on the diagnosis; complete long-term documentation of clinical data and outcome.Consenting clinico-pathological findings in our cohort were consistent with 115 cases showing WHO-ET and 85 patients with prePMF. In comparison to WHO-ET, prePMF revealed minor/borderline age- and gender-matched anemia, slight increase in serum LDH level and leukocyte count, minor to slight splenomegaly, and an occasional left shift in granulo- and erythropoiesis with occurrence of a few myelo-and/or erythroblasts (table 1). An accurate differentiation between both MPN entities was shown to exert a significant difference in terms of overall and relative survival and hematologic transformation into overt PMF and AL. The present study revealed a different CALR mutation frequency in ET in contrast to most of the investigations published recently. We observed CALR mutations in 18% of WHO-ET; JAK2, MPL and CALR wildtype (wt) was observed in 13% of WHO-ET. The discrepancy in the frequencies of CALR positivity in our ET cohort to most of the recently published studies may be due to our strict adherence to the WHO criteria for diagnosis of ET. Regarding prePMF, we observed CALR mutations in 39% of the patients. 92% of the JAK2 and MPL wt subgroup carried the CALR mutation, with JAK2, MPL and CALR wt being observed in only 3% of prePMF.The most remarkable differences between WHO-ET and prePMF were seen in the comparison of the overall survival (figure 1). While the CALR mutation did not have any beneficial influence on survival in WHO-ET, it was associated with a superior overall survival in prePMF. Such a striking difference was not seen at the time of transformation into overt myelofibrosis, and there was only a slightly shorter time to progression to fibrosis in CALR wt prePMFs. There was a trend showing that CALR mutated prePMF patients have shorter thrombosis-free survival compared to CALR wt prePMF patients. There was no impact of the CALR mutations on thrombosis-free survival in WHO-ET.The present data confirm that WHO-ET and prePMF are biologically different sub-entities of MPNs. In prePMF, almost 100% of patients are now associated with a known disease-causing mutation. Our data support the classical clinical approach in the diagnosis of thrombocytosis, using BM histology to differentiate WHO-ET from prePMF and to estimate the outcome of the disease more accurately. Table 1:Total cohort (N=200)WHO-ET (N=115)prePMF (N=85)PAge at diagnosis, years0,04median58,8556,460,7range19-8819-8427-88Sex0,587male784335female1227250Hb, g/dL<0,001median14,114,313,5range8,1-17,68,8-17,68,1-16,6WBC, x109/l0,054median9,258,999,6range4,01-24,544,92-22,34,01-24,54Platelets, x109/l0,739median770770794range78-2530414-249078-2530Palpable splenomegaly<0,001No.51 (12 unk, 1 splenectomy)16 (7 unk, 1 splenectomy)35 (5 unk)%25,513,941,2Fibrotic transformations<0,001No.24 (10 unk)6 (1 unk)18 (9 unk)%125,221,2Thrombotic events0,439No.39 (1 unk)22 (1 unk)17%19,51920prev thrombosis0,042No.503416%2530,418,8JAK2 V617F pos0,08No.1207545%6065,252,9CALR pos0,001No.542133%2718,338,8MPL pos0,189No.844%43,54,7JAK2/MPL/CALR wt0,0029No.18153%9133,5 [Display omitted] DisclosuresThiele:AOP Orphan Pharmaceuticals: Consultancy, Honoraria; Incyte Corporation: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Shire: Consultancy, Honoraria, Research Funding; Sanofi: Consultancy, Honoraria.

Mutations and Long-Term Outcome of 217 Young Patients with Essential Thrombocythemia or Early Primary Myelofibrosis

IntroductionYoung adults with Essential Thrombocythemia (ET) or early Primary Myelofibrosis (early-PMF) are a category of patients projected to a prolonged survival but also to an extended utilization of medical resources. Mutations, including those in the calreticulin (CALR) gene, have been reported to affect main clinical features and outcome in large cohorts of patients with Ph-negative MPNs. However, no data are available on mutational status and long-term outcome in young MPN patients.MethodsA clinic-pathologic database of ET patients followed in 5 Italian Hematology Centers was created. A total of 217 WHO-diagnosed ET or early-PMF patients ≤ 40 years at diagnosis was retrieved from the general database of 2635 patients. All bone marrow biopsies were reviewed at local institution. Baseline clinical/molecular characteristics and outcome measures (thrombosis, hemorrhages, secondary MF and AL, second neoplasia, death, overall and event-free survival) were evaluated. JAK2V617F allele-burden was assessed in granulocyte DNA by using ipsogen JAK2 MutaQuant Kit (qPCR). CALR mutations were identified by next generation sequencing (NGS) approach on GS Junior (Roche-454 platform); MPL mutations were evaluated by using ipsogen MPLW515L/K MutaScreen Kit.ResultsOverall, 197 WHO-defined ET and 20 early-PMF (age range: 16-40, median 34) were included in the study. Mutational frequencies were 61% for JAK2, 25% for CALR, 1% for MPL and 13% for triple negative. Baseline clinical characteristics and use of antiplatelet/cytoreductive therapies were comparable in ET and early-PMF, although frequency of triple negative was higher in the early-PMF cohort.Compared to the JAK2 positive population, both CALR and triple-negative patients showed higher platelet count and lower hemoglobin and hematocrit levels (Table 1).Median follow-up was 10.2 years (range: 0.5-37.5). During follow-up, 19 (9,6%) ET and 3 (15%) early-PMF patients experienced a total of 31 thrombotic (arterial: 38%) and 12 hemorrhagic events, with an incidence rate of 0.91% and 0.39% patients/yr, respectively. The cumulative incidence of thrombosis was 0,14% and 0,24% at 15 and at 20 years, respectively.Overall, 10 patients (4,6%) and 1 (0,4%) patients evolved to MF and AL, respectively; 10 developed a second neoplasia. The cumulative incidence of disease progression into MF/AL was 0,03% and 0,13% at 15 and at 20 years, respectively. At last contact, 6 (2,7%) patients had died, at a median age of 61 years (20-71), for an overall survival of 98% at 15 years. Causes of death were related to the myeloproliferative neoplasm (disease evolution or thrombotic complications) in all patients but one. Event-free survival was similar in the ET/early-PMF cohorts considering both every event separately and all together.In univariate analysis, male sex (p=0.003), previous thrombosis (p=0.001), splenomegaly (p=0.037), JAK2V617F (p=0.019) were associated with increased thrombotic risk; in multivariate Cox analysis, only previous thrombosis and male sex remained significant (p=0.012). Baseline splenomegaly was the only predictive factor for subsequent hemorrhages (p=0.017). Abnormal karyotype was associated with secondary MF (p=0.013) and also with second neoplasia (p<0.001). Together with JAK2V617F positivity and leukocytosis >11x109/L, abnormal karyotype was also associated with worse survival in univariate analysis. However, in multivariate analysis only JAK2V617F mutation remained as negative predictor of survival (p=0.019). Also, multivariable analysis confirmed JAK2 mutation and splenomegaly as independent risk factors for cumulative events.ConclusionsWith the limitations due to the low number of early-PMF, the outcome of young adults with early-PMF and true ET seemed to be comparable. The correlation of abnormal karyotype with MF transformation and second neoplasia suggests the need for an accurate cytogenetic analysis at diagnosis. Mutational status did influence disease phenotype, in terms of baseline characteristics and prognosis. Indeed, JAK2 mutational status confirmed a negative prognostic role for thrombosis and survival, while event-free survival was significantly better in triple-negative patients. Notably, causes of death were mostly related to the hematological malignancy, pointing out the substantial impact that this generally indolent disease may acquire in young adults. [Display omitted] DisclosuresLatagliata:Novartis: Consultancy; Bristol Myers-Squibb: Consultancy; Celgene: Consultancy; Shire: Consultancy. Cavo:Janssen: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; BMS: Consultancy, Honoraria; Millenium: Consultancy, Honoraria; Onyx: Honoraria.

Personalized management of essential thrombocythemia—application of recent evidence to clinical practice

The World Health Organization (WHO) classification system has recently strengthened the diagnostic criteria for essential thrombocythemia (ET) by lowering the threshold platelet count, underscoring its morphological distinction from early/prefibrotic myelofibrosis (MF) and incorporating molecular markers of clonality. The International Working Group for Myeloproliferative Neoplasms Research and Treatment (IWG-MRT) examined the clinical relevance of this process in 1104 cases of locally diagnosed ‘ET' and showed worse overall, leukemia-free and fibrosis-free survival, and a higher risk of bleeding in early/prefibrotic MF (n=180) vs WHO-defined ET (n=891). The risk of thrombosis was similar between the two entities and, in WHO-defined ET, was predicted by thrombosis history, older age, cardiovascular risk factors and JAK2V617F. A prognostic model based on these risk factors identified patient groups in ET with residual risk of thrombosis, despite treatment with conventional therapy. The main objectives of the current perspective are to underscore the prognostic importance of morphological confirmation in the diagnosis of ET and provide management recommendations, in both WHO-defined ET and early/prefibrotic MF, based on observations from the aforementioned IWG-MRT and other studies. In so doing, we are fully cognizant and sympathetic of the fact that some of our recommendations need to be tested in prospective controlled studies.