Essential Thrombocythemia Pts Research Articles

Calr Variant Allele Frequency in Essential Thrombocythemia: Molecular Associations and Impact on Disease Phenotype and Outcome

Background. A mutation in calreticulin ( CALRm) is found in 30-35% of patients (pts) with Essential Thrombocythemia (ET). There are 2 main CALRm mutation types, Type 1/Type 1 like (T1) a 52bp deletion, and Type 2/Type 2 like (T2) a 5bp insertion. Other atypical mutations (T3) occur in a minority of pts. Recent study ( Guglielmelli P et al, BCJ 2023) in pts with myelofibrosis (MF) showed that higher CALR variant allele frequency (VAF) was associated with anemia at diagnosis and during FU, and to features of more advanced disease (CD34 + cell counts, ASXL1 mutation (mut), >2 mutated myeloid genes, and shorter leukocytosis-free survival. Aim. To evaluate whether the CALRm VAF in pts with ET was associated with predefined major clinical outcomes: evolution to MF, transformation to acute leukemia (AML), thrombosis, major bleeding, and survival (OS). Patients and Methods. Diagnosis of ET was strictly according to 2023 WHO and ICC to avoid mis-inclusion of prefibrotic MF. CALRm VAF was determined by capillary gel electrophoresis as the ratio (%) of areas under the curve of CALRm/ CALRm+ CALRwt. A panel of 45 myeloid neoplasm-associated genes was sequenced by NGS. Results. A total of 281 CALRm ET pts were identified from CRIMM (Florence, I), Quebec MPN Research Group centers' (Canada) and Mayo Clinic (Rochester, US) databases; 152 (54%), 101 (36%) and 28 (10%) were T1, T2 and T3 CALRm, respectively. Overall FU was 8.6y (0.3-39.4), median survival was not reached. Rate of death at 10y, 20y and 30y was 8%, 15% and 25%. MF transformation occurred in 50 pts (18%), AML in 2 (0.7%), 25 pts (8.9%) died. A major thrombotic event before or at ET diagnosis occurred in 17 (6.0 %) pts (14 arterial and 3 venous), whereas 28 pts (10.0%) had >1 major thrombosis during follow-up (53.6% arterial, 46.4% venous). Major bleeding occurred in 19 pts (6.8%; 16 at or before diagnosis). Ascertainment of correlation of CALRm VAF with predefined outcomes by continuous variable analysis (ROC curve) highlighted a significant correlation of VAF >60% with MF-free survival (MFS), with HR of 2.85 (95%CI, 1.4-5.6; P= .002. Fig. 1A). On the contrary, there was no impact of CALRm VAF as continuous variable on AML, thrombosis, bleeding and OS. We therefore used a threshold of >60% to compare main clinical and hematologic characteristics at diagnosis and outcomes during FU in pts categorized as CALR-high and CALR-low. Of all pts, 21 (7.5%) harbored a VAF >60%; of these, 52%, 19% and 29% were T1, T2, T3, respectively, compared to 54%, 37%, 8% of CALR-low (P= .008). We found no difference in age, gender, constitutional symptoms, splenomegaly, arterial and venous thrombosis at diagnosis and FU, IPSET revised risk stratification, and bleeding events. Hemoglobin was lower (12.8 g/dL (8.4-14.0) versus 13.6 (10.1-16.0); P=.02), while leukocytes and platelets did not differ. The proportion of pts with additional mutations in myeloid genes was significantly greater in CALR-high pts compared to CALR-low (66.7% vs 30.2%; P=0.01), as it was the proportion of pts with >2 mut myeloid genes (25% vs 11.6%, P=0.04). During FU, 52% of CALR-high pts (n=11) transformed to MF compared to 15% (n=39) of CALR-low (P<.0001); AML and death not differ. Anemia (<10g/dL) during the FU developed in 69% of CALR-high pts vs 18%, leukocytosis (>15x10 9/L) in 46% vs 8% and splenomegaly (greater than 5 cm from LCM) in 50% vs 12% (P<.0001 for all). The HR for anemia-free survival was 2.87 (95%CI, 1.3-6.3), for leukocytosis HR 3.71 (95%CI, 1.3-10.5) and splenomegaly HR 3.40 (95%CI, 1.2-9.2), all P<.01. MFS was significantly shorter in T1 (HR 2.0; P=0.04) or T3 (HR 2.7; P=0.03) using T2 as reference. Finally, we compared C ALR-mut, JAK2V617F mut and triple-negative (TN) ET pts. ROC analysis indicated a JAK2VAF >35% ( JAK2-high) as the best cutoff for shorter MFS. As in Fig. 1B, the MFS survival of CALR-high and JAK2-high was superimposable, and significantly shorter that in CALR/JAK2-low and TN pts. Conclusions. A CALR VAF >60% in pts with ET is associated with greater risk and shorter time to MF progression, development of anemia and splenomegaly. Similar findings in JAK2-high pts reinforce that that accumulation of mutated CALR and JAK2 alleles, evident since diagnosis, is detrimental for evolution to post-ET myelofibrosis. Longitudinal studies after diagnosis might provide further information about the kinetics of allele accumulation.

Restless Legs Syndrome (RLS) in Patients (pts) with Polycythemia Vera (PV): Is Iron Deficiency (ID) the Only Culprit?

Background: RLS is a sensorimotor disorder that causes discomfort in the legs and the urge to move them. In its etiology, there are many conditions including ID. PV is a myeloproliferative neoplasia (MPN), and in pts with PV, ID may develop during the course of the disease. In one study, 29.6% of PV pts had RLS, which was thought to be associated with phlebotomy and ID (Med Oncol. 2010;27(1):105-7). Essential thrombocythemia (ET) is another MPN, in which ID is not typically observed. In our study, we sought to evaluate the frequency of RLS in PV and to search for possible factors other than ID that might have a role in the etiology of RLS among MPN pts. Methods: Previously diagnosed pts with PV and ET, who admitted to our clinic between August and December 2021 were included. All PV pts were evaluated for the study regardless of their iron status. ET pts with ID were not included, since ET cases formed the non-ID MPN control group. Pts with a transferrin saturation below 20% and ferritin level below 20 µg/L were considered as cases with ID. Pts with comorbidities that may lead to RLS generation were excluded. Fasting plasma glucose, HbA1c values, urea, creatinine, thyroid function tests, vitamin B12, and magnesium values were measured. According to these parameters, pts with biochemical disorders that may affect the development of RLS were also excluded (Figure 1). In accordance with the PV and ET groups, pts with ID and healthy subjects (HS) were included as the positive and negative controls, respectively. Demographic characteristics, treatments, complete blood count (CBC) parameters, iron studies, and biochemical tests of the subjects were recorded. Neurological examination was performed in all cases, electromyography (EMG) was taken and evaluated for polyneuropathy. All subjects were questioned according to the RLS diagnostic criteria, and all subjects underwent Pittsburgh Sleep Quality Index (PSQI) tests. Results: In the final analysis, 27 PV, 23 ET, and 22 ID pts and 23 HS were included (Figure 1). Pts in the ID group were significantly younger than other groups (p=0.025) (Table 1). The median follow-up duration of the ET pts was significantly higher than those of others (p=0.011). Other demographic features were comparable between groups (Table 1). No significant pathology was detected in the neurological examination in all subjects. RLS was detected in 25.9%, 34.8%, and 45.5% of PV, ET, and ID pts, respectively. While there was no difference between these groups in terms of the presence of RLS, RLS was not detected in HS. In pts with PV 66% had ID, and there were no significant differences in terms of CBC parameters, iron studies, biochemical parameters, and the JAK2V617F mutational status in PV and ET pts with and without RLS. In addition, polyneuropathy was detected in one ET patient by EMG and RLS was not detected in this patient. There was no significant difference between these groups regarding median PSQI scores, but the median PSQI score was found to be significantly higher in pts with RLS (p=0.001) (Table 1). When we investigated the relationship between cytoreductive treatments and RLS in PV and ET pts, we found that the frequency of RLS was higher in pts receiving interferon-alfa (IFN-a) and anagrelide (Table 2). In pts with PV and ET, IFN-a and anagrelide usage, and magnesium (Mg) levels were found to have an impact on RLS in univariate analysis, but only Mg levels was associated with RLS in multivariate analysis (Table 3). Conclusion: In our study, the high prevalence of RLS in pts with ID and the absence of RLS among HS both indicate that our RLS questionnaire results are reliable. Although not all PV pts had ID, the prevalence of RLS was higher when compared to HS as was described previously (Med Oncol. 2010;27(1):105-7). In addition, although not significantly different, the frequency of RLS was higher in ET pts than that observed in PV cases. These results suggest that, RLS may occur during the course of the disease in MPN pts, due to factors independent of ID and other known RLS triggering conditions. In light of all these, further studies are needed to elucidate the etiology of RLS developing in pts with PV and ET. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

JAK2V617F Molecular Response to Ruxolitinib in Patients with PV and ET Is Associated with Lower Risk of Progression to Secondary Myelofibrosis

Introduction. Ruxolitinib (RUX) is approved for patients (pts) with Polycythemia Vera (PV) who are refractory or intolerant to hydroxycarbamide, based on composite endpoint of spleen volume reduction and Hct control (RESPONSE-1 trial) and Hct control (RESPONSE-2). Conversely, studies in pts with Essential Thrombocythemia (ET) were inconclusive, and the drug is not approved in that indication. Aim. The aim of current study was to analyze changes of JAK2V617F variant allele fraction (VAF) in PV and ET pts who were long-term treated with RUX, and the clinical correlates and outcome of molecular responses. Patients and Methods. The study included 65 PV and 12 ET pts; the latter had been enrolled in phase-2 studies and were still on RUX owing to continuing clinical benefits. Median time from diagnosis to RUX was 5.9y (0.6-24y), age 58y (25-87y), 50.6% were male, history of thrombosis in 21 pts (27%). A JAK2V617F mutation was found in 75 pts (97.4%), JAK2ex12 and MPLW515L in 1 pt each. At circa-annual intervals, JAK2V617F VAF was measured in granulocytes by digital PCR or highly sensitive (threshold <0.01%) RTQ-PCR. MPLW515L was measured by digital PCR. IWG-MRT criteria were used for clinical and molecular response assignment. The latter included partial (PMR: a >50% VAF reduction) and complete (CMR; JAK2V617F undetectable) molecular response, confirmed at >1y. We also considered a deep molecular response (DMR) as a confirmed VAF<2%. The nonparametric Wilcoxon rank-sum test, Kaplan-Meier estimate of survival and log-rank test were used as appropriate. Results. Median FU on RUX was 8.8y (1.3-14.1). The median RUX dose was 20 mg die (5-50mg). RUX was discontinued in 23 pts for AE (n=7, 9.1%), disease progression (n= 12, 15.6%), refractoriness/loss of response (n=3, 3.8%) or pt decision (n=1, 1.3%), after a median of 5.0y (0.8-13y). While on RUX, there were 3 thrombosis and 4 bleedings. Progression to secondary MF (sMF) occurred in 24 pts (31.1%) after a median of 6.0y (2-11.5); of these, 22 (92%) were PV, accounting for 34% of all PV compared to 16.6% of ET. Three pts (3.9%) transformed to AML after 9.2y (1.3-13.7y) and died, and 2 pts (2.6%) died after evolution to sMF while on RUX. A IWG-MRT response was reached in 92% for Hct, 59% for platelet count, 73% for leukocyte count, 77% for spleen volume (<50% palpatory). The median JAK2V617F VAF was 47% (21-98%) and 68% (15-99%) at diagnosis and RUX start, respectively. The overall mean VAF decrease was 64.6%+27.5%. A PMR was observed in 33 pts (44.2%), after a median time of 3.3y (1-7.6y), 51% and 50% of PV and ET; the baseline JAK2V617F VAF was 61.3±27.7% for PV and 32.3±10.4% for ET. A CMR (confirmed) was declared in 5 JAK2V617F mutated pts (6.5%; median baseline VAF 44.7±36.8%) of which 3 were PV, and in the MPLW515L mutated ET pt (baseline VAF 33%). A DMR was confirmed in 9 pts (11.7%; median baseline VAF 30.5±16.0), of which 6 were PV. Median time to CMR and DMR was 4.6y (1.1-7.6y) and 5.0y (2.1-12.1y), respectively. Mean duration of CM + DMR was 8y (7-12y). There was no correlation between any category of molecular response and response of Hct, platelets and spleen length, while normalization of leukocytes occurred more frequently in pts with PMR (93.8% vs 62.5%, P=0.02). Of the pts who progressed to sMF, 21 of 24 pts (87.5%) had not attained an at least PMR (P<0.0001). The HR of sMF evolution was 19.9 (95%CI, 2.4-166.7) for those who did not obtain any molecular response and 3.56 (95%CI, 0.37-34.6) for those who obtained PMR, using CMR+DMR as reference (P<0.0001) (Figure 1). By ROC analysis, a cutoff level of <60% JAK2V617F VAF at baseline (involving 35 pts, 45.5% of the entire population) was associated with a significantly greater likelihood to obtain CMR+DMR (37.1% vs 2.4%; P<0.0001) as well as PMR (60% vs 38.2%, P=0.01). All 3 pts who transformed to AML had not obtained any molecular response. Discussion. In this study, 18% of PV and ET pts receiving RUX developed sustained JAK2V617F complete plus deep molecular response (JAK2V617<2%) over long term treatment, that were associated with lower risk of progression to secondary MF; also pts attaining a PMR had reduced probability to develop sMF compared to those who did not show any changes in JAK2V617 VAF, overall reinforcing that attainment of molecular response may be a surrogate of disease modification. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Clinicohematologic and Molecular Response of Essential Thrombocythemia Patients Treated with Pegylated Interferon-Alpha: A Multicenter Study on Behalf of the German Study Group-MPN (GSG-MPN)

Cytoreductive treatment with hydroxyurea (HU) or anagrelide (ANA) aims at reducing the risk of vascular complications in essential thrombocythemia (ET), while (pegylated) Interferon-α (pegIFN) may also prevent progression to secondary myelofibrosis (SMF) or acute myeloid leukemia (AML). In contrast to polycythemia vera (PV), the accessibility to pegIFN is limited in ET due to lack of approval. To investigate the clinical benefits of pegIFN in ET, we identified within the German Study Group-Myeloproliferative Neoplasms (GSG-MPN) registry a total of 127 WHO-defined patients (pts) treated at seven University centres. In this study, we analysed clinically relevant parameters before and during pegIFN treatment and assessed the JAK2 V617F variant allele frequency (VAF) in DNA from granulocytes by droplet digital PCR (sensitivity 10-3) in JAK2 mutated pts with available biosamples. Baseline characteristics of the pts were: median age at diagnosis 37.0 years (yrs, range 8.2-77.4), median platelet (PLT) count 780 /nl (124-2,776), median white blood cell (WBC) count 8.2 /nl (3.0-17.3); 67% were female; 53% were JAK2 V617F-, 33% CALR-, and 5% MPL-mutated. According to the International Prognostic Score of thrombosis in ET (IPSET), 37% were low-, 31% intermediate-, and 30% high-risk (2% unknown). Median time from diagnosis to pegIFN start was 1.9 yrs (0.0-37.2); in 59% pegIFN was used as first-line drug, 20% were pre-treated with HU, 9% with ANA, and 11% with both. Main reasons for pegIFN start were high PLT count (39%), prior thrombosis (31%), ET-associated symptoms (9%), age >60 yrs (7%), and pregnancy (7%). Since 31 pts (24%) had ≥2 lines of treatment (LOT) with pegIFN, a total number of 161 LOT was recorded. PegIFN 2a was used in most LOT (54%), followed by pegIFN 2b (35%) and ropegIFN 2b (11%). Median total pegIFN treatment duration per pt was 2.3 yrs (0.1-18.1); 30/127 (24%) and 10/127 (8%) were treated for ≥5 yrs and ≥10 yrs, respectively. At last follow-up, 60% of pts were still on pegIFN. The discontinuation rate was highest in the first yr of treatment (14.3%). Adverse events (16%) and market withdrawal of pegIFN 2b (15%) were the two most frequent reasons for discontinuing a LOT. According to European LeukemiaNET response criteria (Barosi et al. Blood 2009), 89% of pts achieved clinicohematologic response at any time which was complete in 54% and partial in 35%. Median PLT and WBC counts at last follow-up (380 /nl and 5.5 /nl, respectively) were significantly lower compared to baseline (780 /nl and 8.2 /nl) (Figure). Only one pt progressed to SMF during pegIFN treatment, while no pt transformed to secondary AML. Vascular complications were rare with three arterial and five venous events in 469 pegIFN treatment yrs, resulting in an incidence of 0.6% and 1.1% per pt and yr, respectively. Flu-like symptoms were recorded in 41%, abnormal liver tests in 16%, and depression in 14% of LOT (grading and time points unknown). Quantitative assessment of the JAK2 V617F VAF on 70 samples from 14 pts with available DNA before pegIFN start and ≥2x thereafter (each at least one yr apart) revealed a reduction from median 30.5% (7.2-48.1) at baseline to 8.3% and 18.1% after 4 and 8 yrs of pegIFN treatment, respectively (n.s.); 5/14 pts (36%) achieved a ≥50% reduction (partial molecular response) and one pt showed a VAF <1%. In 10/127 pts (8%), pegIFN 2b was stopped due to market withdrawal and not immediately switched to an alternative drug as they had been treated for a median of 9.5 yrs (6-18): 3/10 pts maintained normalized blood cell counts until data cut-off (1.5-4.5 yrs after discontinuation); of these 3, one had 0.1% JAK2 V617F at the time of discontinuation, while the other two were JAK2 V617F negative (baseline VAF not available); 2/3 pts underwent bone marrow biopsy and showed histomorphological remission of ET. Analyses of a large series of ET pts treated with pegIFN confirm a high efficacy of the drugs in achieving clinicohematologic response. Our data, including long-term treated pts with low rates of vascular complications, disease progressions, and adverse events underscore the medical benefit of pegIFN in ET. Although reduction of the JAK2 V617F VAF was not significant, molecular responses <1% and histomorphological remissions were observed in single pts. For treatment discontinuation, molecular thresholds for JAK2 V617F and CALR mutations need to be defined in the future. FS and LLT contributed equally to this study. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Measuring the Incidence of Distress and Supportive Oncology Utilization Among Patients with Myeloproliferative Neoplasms: A Single Center Experience

INTRODUCTION Cancer related distress is an experience comprised of physical, psychological, social, and religious/spiritual factors that impact how a patient (pt) copes with illness. High levels of distress have been associated with increased healthcare utilization. NCCN guidelines recommend pts with significant distress be referred to supportive services (SS) within 6 months of screening. Pts with myeloproliferative neoplasms (MPNs) experience a substantial symptom burden that decreases their quality of life. Little is known about the prevalence of distress and the utilization of SS in pts with myelofibrosis (MF), polycythemia vera (PV), and essential thrombocythemia (ET). Hence, we designed and present results of a single center study evaluating levels of distress, SS evaluations, and frequency of hospitalizations in pts with MF, PV, and ET. METHODS Adult pts (age≥18) diagnosed with MF, PV, or ET followed at Levine Cancer Institute (LCI) in Charlotte, NC between 1/1/2017-6/30/21 were included. All included pts were established with a LCI clinician (>1 visit) and had completed an electronic distress survey (EDS), which contained sociodemographic questions and patient-reported outcomes (PROs): distress level, physical symptoms, screening for depression (PHQ-2) and anxiety (GAD-2), daily function, social support, and emotional/spiritual concerns. Pts diagnosed with another hematologic or solid tumor malignancy at the time of survey were excluded. EDS responses, mutations, disease risk assessments, SS visits, ED visits, and hospitalizations were collected retrospectively. Primary objective was to measure the proportion of pts who reported significant distress (score ≥4, based on NCCN guidelines) and were evaluated by ≥1 SS (psychiatry, social work, psychology, chaplaincy, palliative care, and integrative oncology) within 6 months of screening; the proportions with automated referrals based on system triggers (distress score ≥7, GAD-2 ≥5, or PHQ-3 ≥3), unplanned hospitalizations, and ED encounters were also measured. Disease characteristics and PROs were compared between distress groups (score ≥4, 4-6, ≥7) with Fisher's Exact test. Statistical analysis was performed in SAS v9.4; P<0.05 was considered statistically significant. This study was approved by the institutional IRB. RESULTS Pt characteristics and demographics are presented in Table 1. One hundred forty-one pts were included: PV 44 (31%), ET 49 (35%), MF 48 (34%). Median age was 63 years, and 62% were female. Seventy-five (53%) pts reported significant distress, of which 44 (59%) were ≤3 months of diagnosis. Sixty-four percent of PV pts and 60% of MF pts reported significant distress versus 37% of ET pts (P=0.016). SS and healthcare utilization is presented in table 2. The proportion of pts expressing significant distress and being evaluated by SS within 6 months of screening was 33% (n=25). Of 38 (27%) pts who met criteria for an automated referral, 15 (39%) were evaluated by SS within 6 months. Distressed pts (DPTS) had more ED visits (15% vs. 0%, P<0.001) and unplanned hospitalizations (16% vs. 6%, P=0.11). DISCUSSION Despite consensus recommendations, most DPTS were not evaluated by SS. Among DPTS evaluated by SS, social work was most frequently utilized. PV and MF pts were more likely to report distress compared to ET. Limitations to this analysis include lack of data of SS utilization outside of our system, barriers to accessing SS within our system, treatment characteristics, and impact on outcomes. Future work should identify ways to better use patient-reported outcomes to promote early intervention and access to SS. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Spleen and Liver Fibrosis Is Associated to Treatment Response and Prognosis in Philadelphia-Negative Chronic Myeloproliferative Neoplasms

Spleen and Liver Fibrosis Is Associated to Treatment Response and Prognosis in Philadelphia-Negative Chronic Myeloproliferative Neoplasms

Excess Mortality in Young Patients with Myeloproliferative Neoplasms

▪Introduction: Myeloproliferative neoplasms (MPNs) - essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PMF) - are associated with significant morbidity and shortened survival, irrespective of age (Srour et al. Br J Hematol. 2016). Despite shortened survival, young MPN patients (pts) are often classified as “low-risk” and managed with aspirin alone, phlebotomy-only (PHL), or observation instead of potentially life-prolonging cytoreductive and/or disease-modifying treatment. Age-biased risk assessment and treatment practices deprive young pts from early intervention and access to clinical trials. Our goal is to highlight the unmet need for identifying and implementing life-prolonging treatment in young MPN pts. Here, we determine and compare the excess mortality from MPNs in young (<60 years) to older pts (≥60 years) in the United States (US).Methods: In this population-based study, demographic (age, sex, race), survival, and cause-of-death data were collected for MPN pts from the US Survey, Epidemiology, and End Results (SEER) registry between 2001-2017; and for the general US population from the Centers for Disease Control and Prevention Wide-ranging OnLine Data for Epidemiologic Research (CDC WONDER) database. SEER reports cancers classified by International Classification of Diseases for Oncology, version 3 (ICD-O-3), which evolved with the WHO classification of myeloid neoplasms in 2001 for ET, PV and PMF. Cause-of-death is reported by ICD-10 codes, which we categorized into cardiovascular (CVE), second cancers (CA), acute leukemia (AL), and others. Excess, or relative mortality was determined by the ratio of observed mortality in MPN pts (Kaplan-Meier estimate) over the expected mortality of the US population matched by age, sex, race, and birth-year (actuarial estimate). A one-sided log-rank test was used. Excess mortality of young compared to older pts was determined from a random-effects model using restricted maximum-likelihood estimator method. All analyses were performed using RStudio software v 1.4.1106.Results: The SEER query identified 40,333 MPN pts (ET: 17,420 (43%), PV: 18,027 (45%), PMF: 4,886 (12%)) diagnosed at a median age of 66 years (ET: 67, PV: 65, PMF: 69) of whom 20,470 (51%) were females (ET: 10,709 (61%), PV: 7,768 (43%), PMF: 1,993 (41%)). The 10-year mortality for ET, PV, and PMF pts <60 was 13%, 18%, and 49% respectively (versus 6% for controls); and ≥60 was 59%, 59%, and 87% respectively (versus 35% for controls) (Figure 1A). Excess all-cause mortality was higher in pts <60 compared to ≥60 with ET (2.75 versus 1.82, p<0.001), PV (3.16 versus 1.92, p<0.001), and PMF (10.6 versus 5.73, p<0.001) (Figure 1B). Excess CVE mortality was higher in PV<60 compared to PV≥60 (3.36 versus 2.55, p=0.036) but not in ET or PMF. Excess CA mortality was higher in PV<60 than PV≥60 (2.36 versus 1.53, p=0.002) but not in ET or PMF. Excess AL mortality was high for all pts, particularly PMF, and was not significantly different in pts <60 compared to ≥60Discussion: Excess or relative mortality emphasizes the burden of MPN-related death with current treatment. In this population-based study, we found excess mortality in young MPN pts (<60), greater than in older pts (≥60). This difference may result from age-biased risk assessment and treatment recommendations that recommend lower intensity therapy for young pts. It may be time to revisit these recommendations since accruing evidence demonstrates long-term safety, efficacy and potential survival benefit of available cytoreductive agents. Certain treatments such as interferon-alpha (IFN) may improve survival in PV (Abu-Zeinah et al. Leukemia. 2021), and a recent randomized clinical trial established superiority of IFN over standard of care PHL in young PV pts (Barbui et al. Lancet Hematol. 2021). These data advocate for early intervention with potentially disease-modifying treatment for all pts regardless of age. These data also call into question age-biased exclusions of many young pts from participation in clinical trials of established or promising drugs.Conclusion: Excess mortality of young MPN pts (<60) is unacceptably high and greater than that of older pts (≥60). Clinical trials testing early intervention with potentially life-prolonging treatments are required. [Display omitted] DisclosuresSilver: Abbvie: Consultancy; PharamEssentia: Consultancy, Speakers Bureau. Scandura: Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Constellation: Research Funding; MPN-RF (Foundation): Research Funding; CR&T (Foudation): Research Funding; European Leukemia net: Honoraria, Other: travel fees . Abu-Zeinah: PharmaEssentia: Consultancy.

Critical Evaluation of Who 2016 Criteria for the Diagnosis of Polycythemia Vera: Distinction from JAK2V617+ Essential Thrombocythemia

IntroductionThe JAK2V617F and exon 12 mutations are critical for the diagnosis of polycythemia vera (PV) and JAK2V617F is the molecular marker of 50-60% of patients (pts) with essential thrombocythemia (ET) [Arber, DA et al. Blood. 2016;127:2391-2405]. Distinguishing these illnesses in their early stage remains a clinical problem because of this shared mutation and phenotypic characteristics [Silver, RT et al. Blood. 2013;122:1881-1886][Ancochea, A et al. Br J Haematol. 2014;167:411-417]. When the hematocrit (HCT), red blood cell (RBC) count, or hemoglobin (HGB) are increased, we distinguish PV from JAK2V617F -mutated(JAK2V617F +) ET using chromium-51 (Cr-51) labeled RBC to measure red cell mass (RCM) and iodine-135 (I135) to determine plasma volume. To define polycythemia, the World Health Organization (WHO) 2016 criteria used HCT and HGB values derived from a retrospective study which have never been confirmed [Arber].Materials and MethodsWe diagnosed PV by establishing JAK2V617F positivity, a Cr-51 measured RCM>125% of expected volume, and a marrow biopsy consistent with PV [Silver]. Utilizing a receiver operating characteristic (ROC) analysis [IBM SPSS, 23.0], we determined threshold values for HCT, HGB, and RBC to distinguish 69 PV pts from 31 JAK2V617F + ET pts who presented with “high-normal” HCT or HGB values.Results:Relevant demographic and hematologic data are shown in Table 1. The Cr-51 determined RCM of all 69 PV pts was >125%, establishing polycythemia [Silver], and was measured in 28/31 JAK2V617F + ET pts; it was normal in all (mean=95.6 ±13.1%).ROC analyses were performed to determine threshold HCT, HGB, and RBC values to distinguish PV from JAK2 V617F + ET pts. For men and women, respectively, the HCT threshold values were 49.3 and 45.8%, for HGB 16.8 and 15.2 g/dL, and for RBC 5.79 and 5.125 x106/uL . These values and those proposed by WHO 2016 are shown in Table 2. The area under the curve (AUC) for the Cr-51 RCM was 1, indicating 100.0% diagnostic specificity (spec) and sensitivity (sens) for distinguishing PV from JAK2 V617F + ET (AUC measures how well groups are distinguished and can range from 0 to 1, with 1 representing a perfect test). Figure 1 shows ROC curves representing the spec and sens of using HCT to distinguish PV from JAK2V617F+ ET. For men, the AUC for HCT was 0.846 (spec=100.0%, sens=64.9%), for HGB 0.753 (spec=100.0%, sens=55.6%), and for RBC 0.761 (spec=100.0%, sens=77.4%). For women, the AUC for HCT was 0.974 (spec=95.7%, sens=78.1%), for HGB 0.875 (spec=95.5%, sens=77.4%), and for RBC 0.924 (spec=90.9%, sens=88.0%). Blood values were less sensitive in men than in women, whereas the specificities were consistent (Table 2). Distribution curves plotted for HCT, HGB, and RBC values are shown in Figure 2. For pts with PV or JAK2V617F+ ET, the HCT values overlap in 40.8% of men and 18.3% of women. The HGB values overlap in 49.0% of men and 53.6% of women, and the RBC values overlap in 53.3% of men and 50.0% of women.Discussion:The Cr-51 RCM was 100% specific and sensitive for distinguishing PV from JAK2V617F+ ET. Our HCT and HGB values derived at the time of the diagnostic Cr-51 RCM from PV pts are concordant with those of WHO 2016 for diagnosing PV [Arber]. However, there is substantial overlap in HCT values occurring in 40.8% of men and 18.3% of women, and in HGB values occurring in 49.0% of men and 53.6% of women, which indicates low sensitivity for distinguishing PV from JAK2V617F+ ET. In the absence of performing a Cr-51 RCM, a marrow biopsy is mandatory for distinguishing them. It has been suggested that JAK2V617F + ET pts are at higher risk for thrombosis than calreticulin-mutated ET [Rumi, E et al. Blood. 123;10:1544-1551]. Since median HCT values were not reported and since neither isotope studies nor systematic marrow biopsies were performed, some alleged JAK2V617F+ ET pts who had a higher risk of thrombotic events may actually have had PV.Conclusion:Of importance, this is the first confirmation of WHO 2016 values for the diagnosis of PV. However, these values do not provide unequivocal separation of PV from JAK2V617F+ ET. In these cases, in the absence of a Cr-51 RCM, a marrow biopsy is mandatory because its distinction has serious prognostic and therapeutic implications. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Circulating Platelet Vs Megakaryocyte-Derived Microparticles Identify Myelofibrosis Patients with JAK2V617F Mutation, High Disease Burden and Ruxolitinib Response

Myelofibrosis (MF) is a clonal neoplasia of the hematopoietic stem/progenitor cells characterized by distinctive abnormalities in megakaryocyte (MK) development and platelet (PLT) activation. Therapy with Ruxolitinib (RUX), a JAK1/2 inhibitor, suppresses both clonal myeloproliferation and release of proinflammatory cytokines, reducing splenomegaly and constitutional symptoms in around half of patients (pts). However, a deeply understanding of the activated inflammatory pathways and the biological effects of RUX is still lacking. Microparticles (MPs) produced by cells may occur as a key cellular communication process in homeostasis, which may increase under inflammatory stimuli and neoplastic diseases. Most of circulating MPs are of PLT and MK origin. Their role and modulation in the inflammatory microenvironment of MF are elusive.We evaluated whether circulating MK and PLT-derived MPs are dysregulated in MF and how the inflammatory microenvironment may drive their pattern. Also, we investigated whether circulating MK and PLT-derived MPs may be considered as a novel biomarker of response to RUX.EDTA-anticoagulated peripheral blood (PB) was collected from 42 MF pts, 13 Polycythemia Vera (PV)/Essential Thrombocythemia (ET) pts and 10 age/sex-matched healthy donors (HD). Samples from MF, ET/PV pts were obtained at diagnosis or out of cytotoxic treatment for at least 3 months; 14 MF pts were studied also after 6 months of RUX therapy. Spleen response (SR) was evaluated according to the 2013 IWG-MRT criteria. PLT (CD61+CD62P+) and MK (CD61+CD62P-)-derived MPs were analysed in PLT poor plasma samples by flow cytometry (CytoFLEX, Beckman Coulter, MPs ranging 0.5-0.9 μm).MF pts were JAK2V617F (n=24), CALR (n=9) and MPL (n=4) mutated; 5 pts were TN . The mean percentage of PLT-derived MPs of JAK2V617F mutated pts was significantly increased as compared with HD (p<0.05; Fig. 1A). On the contrary, as a sort of compensatory mechanism, the mean percentages of MK-derived MPs were significantly decreased in JAK2V617Fand TN pts as compared to HD (p<0.05, respectively; Fig. 1B). Interestingly, among MPNs, PLT-derived MPs were significantly increased in ET pts only as compared with HD (p<0.05).MF pts were at low/intm-1 (n=16), or at intm-2/high IPSS score (n=26). Higher-risk (HR)- JAK2V617F pts only showed a significantly increase of PLT-derived MPs along with a significant decrease in the percentage of MK-derived MPs as compared to lower risk (LR)- JAK2V617F and HD (p<0,0001, respectively; Fig. 1C-D).Remarkably, at baseline, contrary to pts with no response (NR; n=7), pts achieving a SR (R; n=7) showed a low PLT-/MK-derived MPs ratio (Fig. E, baseline), as result of the reduction of MK-derived MPs in NR pts (p<0,05) (Fig. 1G). Accordingly, it may prompt to consider this ratio as potential predictive marker to RUX response. After 6 months of RUX, the PLT-/MK-derived MPs ratio of R pts was significantly decreased as compared with that of NR pts (p<0,01) (Fig. 1E, 6-months post-RUX); this is mainly due to the strong reduction of PLT-derived MPs in R pts (p<0,001) (Fig. 1F).To evaluate whether inflammatory status may play as a key regulator of MPs, we correlated the level of crucial inflammatory factors (Interferon (IFN)-γ, Interleukin (IL)-1β, IL-6, IL-8, Tumor Necrosis factor (TNF)-α, Thrombopoietin (TPO)) to circulating MPs. Surprisingly, we reported a highly inverse relationship between levels of IFN-γ (r=-0,5534; p<0,01), IL-1β (r=-0,4648; p<0,01), TNF-α (r=-0,4444; p<0,05) and MK-derived MPs percentages, highlighting an impaired response to inflammation. Concomitantly, we observed a positive correlation between IL8 with MK-derived MPs hinted at its implication in MK dysregulation. The percentages of PLT-derived MPs were positively correlated with only TPO plasma levels (r=0.4299; p<0.05), that may influence PLT/MK-derived MPs ratio by activating PLT.Overall our results demonstrate that in MF pts the inflammatory status may contribute to drive MK and PLT-derived MPs dysregulation. We also show that the mutation status impacts the proportion of circulating MK-and PLT-derived MPs, suggesting a role of mutated JAK2 in MPs biogenesis/clearance and, ultimately, in cell (MK, PLT) to cell communication. Interestingly, MK vs PLT-derived MPs pattern may be a biomarker of disease identifying JAK2V617F -mutated pts at high IPSS risk and RUX responsive.DF, MB, FR and FP, LC equally contributed [Display omitted] DisclosuresMartinelli:Ariad/Incyte: Consultancy; Pfizer: Consultancy; Celgene: Consultancy; Amgen: Consultancy; Johnson&Johnson: Consultancy; Roche: Consultancy.

Phenotypes of JAK2-Mutated Polycythemia Vera and Essential Thrombocythemia with and without Thromboembolic Events: Results of the Hinc-207 (OSHO #91) Study

Thrombosis is the major cause of morbidity and mortality in polycythemia vera (PV) and essential thrombocythemia (ET). Age ≥60 years (y) and/or history of thrombosis labels patients (pts) as high-risk for thrombosis. Yet, thrombosis frequently occurs prior to the diagnosis of PV/ET. In a multicenter study of the East German Study Group (HINC-207; OSHO #091), the interaction between age and time occurrence of the first thrombosis as risk factors for thrombosis after diagnosis was studied. Methods After IRB approvals, JAK2 mutated adults with PV or ET were prospectively enrolled in 9 centers and centrally stratified in a one to two ratio (group A: pts with a history of thrombosis; group B: pts without thrombosis) with a pre-planned minimum of 60:120 pts. Based on a longitudinal and cross-sectional design, clinical and laboratory data at diagnosis, last follow-up, and thrombosis (for group A) were collected. Thrombosis prior to diagnosis was labeled as A1 and thrombosis after diagnosis as A2. Thrombosis risk factors were grouped into age-, previous thrombosis-, thrombosis prior to PV/ET-, cardiovascular (CV)-, thrombophilia-, and disease- (JAK2 allele burden, Hct, and WBC) related. Additionally, therapies [aspirin (ASS), anticoagulation, phlebotomy, and cytoreduction] and data from a study-own patient questionnaire were included. All pts signed informed consent. The primary endpoint was the phenotypic diversity in JAK2-mutated ET and PV pts with or without thrombosis. Results From April to Dec, 2019, 246 pts were recruited. Data on 237 pts (median age 62y; 59% females, 58% PV) are available. At diagnosis, pts in group A (n=71, median age 59.5y) tended to be younger than those in group B (n=166, median age 63y) (p=0.07). Yet, 70.4% thrombotic events (venous: median age 46.5y; arterial: median age 57y) occurred in A1 and correlated with younger age (p=0.03). Only 3 pts developed a second event after diagnosis. These were counted in A2 (n=24, median age at thrombosis: 61y). Overall, thrombosis occurred either prior to or within the first 3y after diagnosis in 63/71 (89%) pts. Age&amp;gt;60y could not be identified as a risk factor for thrombosis or type of thrombosis at any time point. The 5 y probability of no thrombotic event after diagnosis in pts &amp;gt;60y was 90.4% vs. 89.2% for pts &amp;lt;60y (p=0.8) and that of a thrombotic event &amp;gt;3y after diagnosis in pts &amp;gt;60y was 3.7% vs. 4.9% for pts &amp;lt;60y (p=0.7). Similarly, A1 did not correlate with A2 (p=0.3). With 1691 patient-years for the entire cohort, the incidence of thrombosis after PV/ET diagnosis was 0.7 for arterial and 0.6 for venous events per 100 patient-years. Smoking was more prevalent in pts &amp;gt;60y (p=0.003) and was not associated with thrombosis. Irrespective of age, hypertension (65%, p=0.03), hyperlipidemia (19%, p=0.008), and diabetes (16.4%, p=0.05) were frequent and correlated with A2 while atrial fibrillation (p=0.03) and inherited thrombophilia risk factors (p&amp;lt;0.00) with A1. JAK2 allele burden (median 19%) and Hct &amp;gt;45% (median 45%) at diagnosis correlated strongly with age &amp;gt;60y (p=0.005) but not with A, A1, or A2, although Hct &amp;gt;45% at diagnosis correlated with A2 in PV (p=0.001). Surprisingly, a Hct &amp;gt;45% at thrombosis was more frequently present in A1 (55%) vs A2 (30%) (p&amp;lt;0.00). Median WBC at diagnosis was higher in B compared to A (p=0.004), strongly associated with age &amp;gt;60y (p&amp;lt;0.00) but not with A2. WBC &amp;gt;15% at thrombosis did not correlate with A. Age rather than thrombosis was the trigger for cytoreduction [82% hydroxyurea (HU) in B pts &amp;gt;60y vs 53% in A pts &amp;lt;60y] (p&amp;lt;0.00). In PV, ASS did not correlate with thrombosis (25% of pts in B did not receive ASS). Cytoreduction, interval between diagnosis and cytoreduction, nor the duration of exposure correlated with thrombosis. Conclusions: The majority of thrombotic events occurred prior to or within the first 3 years after the diagnosis of JAK2 mutated PV/ET and were associated with CV-risk factors rather than older age. Phenotypic features such as Hct &amp;gt;45%, high WBC, and JAK2 allele burden were associated with age &amp;gt;60y and less with thrombosis. Their value as surrogate markers for therapeutic interventions to reduce thrombosis needs to be critically evaluated in larger series. Whether adequate PV/ET- or CV-risk- treatments account for the low rate of CV events after diagnosis (despite a higher incidence of CV-risk factors) compared to the general population could not be answered due to study design and needs to be addressed prospectively. Disclosures Al-Ali: Novartis: Honoraria, Research Funding; Celgene: Honoraria, Research Funding.

Highly Reduced Survival in ET and PV Patients with Vascular Complications during Follow-up - Real World Data from the Swedish MPN Registr

Background Patients diagnosed with myeloproliferative neoplasms (MPNs) are at an increased risk of vascular events. A paucity of population-based studies investigating risk factors exist. We conducted a nested case-control study to explore the relative importance of risk factors, treatment, and blood counts for vascular complications in Essential Thrombocythemia (ET) and Polycythemia Vera (PV), and their impact on life expectancy. Patients and Methods All newly diagnosed MPN patients (pts) are reported to the Swedish national MPN registry as mandated by Swedish law. 922 ET pts and 763 PV pts diagnosed from January 2010 through September 2015 with a 3 or 6-year follow-up were included. Pts identified as having a vascular complication were assigned a control patient matched by MPN subtype, gender and age. Blood counts, EPO and JAK2V617F mutation status at diagnosis were recorded, as was co-morbidity, smoking habits and vascular complications prior to diagnosis. At the time of vascular complication cytoreduction, anti-thrombotic therapy and blood counts were investigated. In controls these parameters were registered at the corresponding time from diagnosis. MPN therapy is recommended in Nordic guidelines that closely mirror those issued by the ELN. Statistical analyses Differences in the distribution of variables were analyzed using Mann-Whitney test. Chi square test was used for comparison between groups. Overall survival estimations were calculated by Kaplan-Meier analysis and compared using Log Rank test. Multivariate analysis was performed by unconditional logistic regression. Results At diagnosis ET and PV pts with complications were older compared to the whole ET and PV cohorts, mean ages 73 and 65 years respectively in ET (p&lt;0.001), 73 and 68 years in PV (p&lt;0.001). No significant differences in blood counts, EPO, JAK2 V617F mutation status or vascular events prior to diagnosis were seen compared to the whole cohorts. Neither did cardiovascular risk factors nor smoking habits differ. The vast majority of pts in the study were high risk according to ELN criteria. Seventy-one ET pts (8%) suffered at least one vascular complication during follow-up. 49 thromboembolic and 22 hemorrhagic; 1.4 and 0.6 events/100 patient-years respectively. Median time from diagnosis to vascular complication was 24 months (0-71). Most common thromboembolic events were cardiac, DVT/LE and cerebral. Gastrointestinal (GI) and cerebral were the most frequent hemorrhagic complications. At time of event there were no significant differences in mean hemoglobin (Hgb), hematocrit (Hct) or platelet counts. Mean white blood cell (WBC) count was 9.1 x109/L in the complication group compared to 7.1 x109/L in controls (p=0.063). Frequent use of cytoreductive therapy and/or anti-thrombotics may have contributed to a lack of difference between treated and untreated pts in ET. 81 (11%) of the PV pts had at least one vascular event after a median time of 24 months (0-89). 59 of these thromboembolic and 22 hemorrhagic; 2.5 and 0.9 events/100 patient-years respectively. Cerebral ischemic events were the most frequent, followed by DVT/LE and cardiac, in hemorrhage G-I and cerebral. At time of vascular event the mean WBC was 13.5 x109/L compared to 9.6 x109/L in controls (p&lt;0.001). No significant differences were found in Hgb, Hct or platelets. Cytoreductive therapy was given to 51% of complication pts compared to 79% of controls (p&lt;0.001). Similar differences were found in use of anti-thrombotic prophylaxis; 86% compared with 99% (p=0.007). In multivariate analysis, only cytoreductive therapy, odds ratio (OR) 0.26 (p=0.001) and antithrombotic therapy OR 0.10 (p=0.043) remained as significant protective factors. The estimated 5-year survival was significantly impaired in ET pts who suffered a vascular event compared the matched controls without vascular complication, 65% and 81%, respectively (p=0.020). The same was seen in PV, 60% compared to 85% in the controls (p&lt;0.001). Causes of death will be reported. Conclusions In this population-based study the main finding was that survival of PV and ET pts with vascular complications is highly reduced compared to controls. At the time of complication blood values, with the exception of WBC in PV, do not show any significance. This finding clearly demonstrates that the cytoreductive treatment per se is protective, and underscores the negative impact of undertreatment in PV. Figure Disclosures Samuelsson: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; CTI Bio: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; AOP Pharma: Honoraria.

PF681 IMPACT OF MYELOPROLIFERATIVE NEOPLASMS (MPNS) AND PERCEPTIONS OF TREATMENT GOALS AMONGST PHYSICIANS AND PATIENTS IN 6 COUNTRIES: AN EXPANSION OF THE MPN LANDMARK SURVEY

Background:Previous patient (pt) and physician surveys in North America, Europe and Japan have extensively documented the high symptom burden associated with myeloproliferative neoplasms (MPNs) such as myelofibrosis (MF), polycythemia vera (PV) and essential thrombocythemia (ET). No such data are available for the rest of the world.Aims:To evaluate pt‐ and physician‐reported perceptions of symptom burden, treatment goals and disease management.Methods:A cross‐sectional survey of pts with MPNs and physicians treating pts with MPNs was conducted in China, Turkey, Russia, Taiwan, South Korea and Saudi Arabia. No pt data were collected in Saudi Arabia. Independently recruited respondents completed an online survey measuring their perceptions of the impact of MPNs.Results:A total of 506 pts (MF: n = 147; PV: n = 168; ET: n = 191) completed the survey (52% female; median patient age ± SD: 60.0 ± 10.69 years). Most pts were experiencing symptoms for ≤1 year prior to MPN diagnosis (83%). A total of 240 physicians (68% hematologists, 32% hemato‐oncologists) completed the survey. At consultation, only 36% of physicians used a validated symptom assessment form; 39% used their own rating method. Many pts also did not recognize that their symptoms could be MPN‐related. For example, fatigue/tiredness was one of the most commonly reported symptoms to physicians (69% MF, 40% PV, 54% ET); however, many pts did not think their fatigue resulted from MPNs (18% MF, 25% PV, 18% ET). Consistent with this, physicians (43%) indicated that pts could only identify few/some of their symptoms as MPN‐related.A high proportion of physicians (94%) and pts (82%) felt that MPN symptoms reduce a pts’ quality of life (QoL). Furthermore, 83% of physicians reported that even mild‐moderate symptoms can have a negative impact on QoL.Despite this, while more physicians than pts ranked a better QoL as a key treatment goal, reducing MPN symptoms seemed to be a priority more commonly for pts (72% MF; 68% PV; 68% ET) than physicians (61% MF, 43% PV, 55% ET) (Figure). Slowing/delay in disease progression as a treatment goal was more common for physicians than pts in PV.As well as a high symptom prevalence, pts reported a substantial emotional burden associated with their disease: 78% MF, 59% PV and 57% ET pts were anxious/worried about their condition. Overall, a high burden on activities of daily living (ADL) was reported, especially in MF.Only 28% physicians felt in complete agreement with their pts on treatment goals. Furthermore, one quarter of pts were dissatisfied with their doctor's understanding and support of their treatment goals, and pts reported often feeling worse than their physician was aware (62% MF; 42% PV; 47% ET). Interestingly, approximately half of pts still expressed high satisfaction with their doctor's management and treatment of their MPN.Summary/Conclusion:This study revealed a lack of understanding of MPN symptoms among pts; physicians agreed that their pts could identify few MPN‐related symptoms. Although physicians acknowledge adverse impact of symptoms on QoL, more pts than physicians see reducing symptoms as a treatment goal. Despite reported pt satisfaction in disease management, pt‐ physician disconnects are apparent, demonstrating a need for improved communication. A need for standardization in symptom assessment was also highlighted, which could result in improved pt understanding of MPNs. Subtle differences from survey results in other geographies would be discussed.image

Next-Generation Sequencing (NGS) in Childhood Myeloproliferative Diseases (MPD)

Driver mutations of JAK2, CALR and MPL are found in >90% of adults with BCR-ABL1-negative myeloproliferative neoplasms (MPN). In children, the presence of clonal markers ranges between 22 and 40%, and inherited forms of MPD, such as familial erythrocytosis (FE) and hereditary thrombocytosis (HT), are common. Data on the mutational spectrum and biology of childhood MPD are limited. The aims of this study were: a) to evaluate the ability of a next-generation sequencing (NGS)-based 44-gene analysis to better characterize wild type (WT) MPD, and b) to identify non-canonical and/or non-driver mutations in children and adolescents with MPD.Eighty patients (pts) aged ≤20 years (yrs) at diagnosis of MPD, observed between June 1980 and September 2015, were first investigated with standardized methods for driver mutations of MPN (JAK, MPL, CALR), for genes involved in FE (HRE, EpoR, HIF2α, HIF1α, VHL, PHD1-3, STAT5, LNK, TET2) and HT (THPO, MPL, LNK and TET2). Then, a 44-gene panel providing diagnostic information in myeloid malignancies and in rare inherited erythrocytosis/thrombocytosis (JAK2, CALR, MPL, ASXL1, CBL, C-Kit, CSF3R, CUX1, DNMT3A, ETNK1, EZH2, IDH1, IDH2, IKZF1, KRAS, LNK, NFE2, NRAS, PTPN11, RUNX1, SETBP1, SF3B1, SRSF2, TET2, TP53, U2AF1, ZRSR2, BPGM, EGLN1 (PHD2), EPAS1 (HIF2A), EPOR, GATA1, GELSOLIN, HBA1, HBA2, HBB, JAK2,MPL, RUNX1, SH2B3, SRC, THPO, VHL, WAS) was employed to better characterize these diseases. Sequencing analyses of DNA from mononuclear peripheral blood cells were performed in 57/80 pts.Eighty pts (M 41, F 39; median age at diagnosis: 149/12 yrs, range 3 months-1911/12 yrs), investigated by standardized methods, were retrospectively classified according to the WHO 2016 criteria as follows: 35 essential thrombocythemia (ET) (10 JAK2V617F, 2 CALR type1, 6 CALR type2, 1 CALR atypical, 16 WT), 9 polycythemia vera (PV) (4 JAK2V617F, 5 WT) and 3 primary myelofibrosis (PMF) (1 JAK2V617F, 2 WT). Twenty-three pts with MPLS505N or MPLV501A mutations and 10 pts with HIF mutations (3 pts) and/or anamnestic criteria of FE (7 WT) were considered HT and FE, respectively. The NGS-based 44-gene panel was applied to 57 MPD pts (11 JAK2V617F, 6 CALR, 12 MPLS505N, 2 MPLV501A, 3 HIF2α and 23 WT). According to the WHO 2016 criteria, 27 pts were ET, 14 HT, 8 FE, 7 PV and 1 PMF. By using the NGS panel, clonal markers were found in 12/23 (52%) pts with MPN WT: HBB and PDH2 in 2 FE, MPLW515_P518>KT in 1 ET pt and non-driver mutations in 9 pts (7 ET, 1 PF and 1 PV). Furthermore, two non-canonical driver mutations, MPLC322G and JAK2G301R were identified in 1 CALR type2 ET and in 1 JAK2V617F PV, respectively. An additional MPLV501M mutation was found in 1 MPLS505N HT. Taken together, among the 57 pts 18 (32%) had one (11/18=68%) or two (7/18=39%) non-driver mutations. Eight of the 34 pts (23.5%) with a clonal marker had additional non-driver mutations, that was single in 6 pts. Within the familial MPD, a single non-driver mutation was found in 3/8 FE pts (37.5%), while no mutations were detected in HT pts. Considering the functional classification of non-driver mutations, we found mutations in signaling (CBL, LNK/SH2B3, CSF3R, KIT, SETBP1) and splicing (U2AF1, ZRSR2) genes in ET and PMF pts, and mutations of epigenetic regulation genes (TET2, ASXL1, DNMT3A) in PV, FE and ET pts (Table 1). The co-occurrence of driver and non-driver mutations in the same individual is illustrated in the circos plot (Figure 1).The use of a NGS-based 44-gene panel in acquired and familial pediatric MPD enabled to identify driver and non-driver mutations, not otherwise detected by conventional methods, with a substantial proportion of MPD pts (81%) showing mutations in the genes analyzed. Interestingly, we found additional neoplastic mutations in some pts with FE. Although the utilized NGS-based panel proved useful to better characterize children and adolescents with MPD, 19% of our pts still remain without any identified clonal marker. Further targeted NGS and whole genome sequencing may enable to better define MPD children without molecular markers. [Display omitted] DisclosuresMalaspina:Sapienza University, Rome: Other: Resident in Hematology. Foà:ABBVIE: Other: ADVISORY BOARD, Speakers Bureau; CELGENE: Other: ADVISORY BOARD, Speakers Bureau; AMGEN: Other: ADVISORY BOARD; INCYTE: Other: ADVISORY BOARD; NOVARTIS: Speakers Bureau; ROCHE: Other: ADVISORY BOARD, Speakers Bureau; GILEAD: Speakers Bureau; JANSSEN: Other: ADVISORY BOARD, Speakers Bureau; CELTRION: Other: ADVISORY BOARD.

Comparative Genomic and Expression Analysis of Chronic and Blast-Phase Cells in Patients with Myeloproliferative Neoplasms

Background. Progression to acute myeloid leukemia (sAML) occurs in 20% of myelofibrosis (MF) and 10% of polycythemia vera (PV) or essential thrombocythemia (ET). sAML has dismal outcome with median survival of <6 months. We recently reported that a restricted set of mutations predict for leukemic transformation in MPN (Vannucchi AM, Leukemia 2013; Tefferi A, Blood Adv. 2016). However, the molecular mechanisms underlying transformation to sAML are poorly characterized, in particular the relationships between the clones establishing the chronic phase and the one dominating the leukemic phase.Aim. To study clonal heterogeneity and clonal progression in the leukemic transformation of MPN we performed whole exome (WES) and trascriptome (RNAseq) sequencing of paired samples (chronic (CP)/blast phase(BP).Patients and Methods. WES and RNAseq was done on CD34+ or blast cells of 12 paired samples from 5 PMF, 3 PET-MF, 1 PPV-MF, 3 ET pts who transformed to sAML. In addition, a myeloid neoplasm-relevant 34-gene panel was used for target NGS sequencing of paired samples plus an additional 23 samples collected from MPN pts at leukemic phase (15 PMF, 3 PET-MF, 3 ET, 2 PV).Results. In the entire series, 20 pts (57%) were JAK2 V617F mutated at CP, 8 CALR (23%; 6 type-1 and 2 type-2) and 7 (8.6%) MPL mut, while 4 (11.4%) were triple-negative. JAK2 variant allele frequency (VAF) declined by ≥50% (n=3; 15%) or became undetectable (n=4; 20%) whereas 3 heterozygous pts (15%) became homozygous at the time of BP. One of the 8 CALR mut cases halved its VAF, whereas no meaningful VAF changes were observed in MPL mut pts. The most frequent mutated genes detected by NGS at BP, other than driver mutations, were ASXL1 (51.4%), RUNX1 (37.1%), TET2 (17%), SRSF2 (16%), IDH1 (14%), TP53 (14%), NRAS (14%), FLT3 (14%), U2AF1 (11%) and KRAS (11%); three (8%) cases were mutated for EZH2DNMT3A, CBL and PTPN11, 2 cases for IDH2, SH2B3, SF3B1 IKZF1, SETBP1 and ZRSR2, and 1 case for ABL1, ATV6, BRAF and ARID1A. There were also 5 CEBPA-mutated pts, 3 of which, unlike none of 27 CEBPA-mutated de novo AML, showed an in-frame 6-bp duplication polymorphism (p. P196_197insHP) reported in 20-40% of all de novo AML and <1% of healthy population (rs762459325). Compared to the CP of the 12 paired samples, 10 pts (83%) acquired novel mutations, 3 of which acquired ≥3 variants. RUNX1 and ASXL1 were those with the highest number of acquisition (n=7 and 5, respectively). Conversely, loss of variants was observed only in ASXL1 (n=3).By WES analysis, on average 60.000 variants per paired sample unique to the BP compared with CP were identified. However, no recurrent abnormalities were found in the 12 paired samples outside the above listed mutations found by target sequencing. For RNAseq analysis, transcripts were annotated according to UCSC hg19 for a total of 25,369 genes. We found large transcriptional differences between CP and BP with 129 transcripts differentially expressed (23 up- and 106 down-regulated) and 4,155 isoforms (2,120 up- and 2,035 down-regulated). Among the most abnormally expressed transcripts we selected 8 genes (5 down-regulated: LCN2, PDGFB, PRTG, CRISP3, PF4; 3 up-regulated CDKN2, SH2D1A and LIN28) for validation by QRT-PCR based on the extent of differential expression. PF4 and CDKN2 were confirmed to be down-regulated and over-expressed in BP, respectively (P<0.0001). Analysis of RNA-seq data for fusion genes revealed 10 fusion genes acquired during BP; however, only 3 of them were confirmed by Sanger sequencing (2 cases of BCR-ABL, 1 case of KMT2A- MLLT3 and 1 case of CBFB-MYH11). Pathway analysis included Gene Set Enrichment Analysis and Signaling Pathway Impact Analysis. Six pathways were significantly deregulated in BP compared with CP: Mitotic Spindle (P<0.0001); Androgen response (P=0.004); TGF-beta signaling (P=0.04); Apoptosis (P=0.03); PI3K-AKT-MTOR signaling (P=0.04); Reactive Oxygen Species- Pathway (P=0.03).Conclusions. Comprehensive comparative analysis of genomic and RNA abnormalities acquired in the transition from CP to BP in MPN has not been previously reported. Our data indicate that BP is associated with significant changes in mutation complexity and RNA expression, overall affecting different intracellular pathways whose further characterization might help to identifying potential targets for therapy. DisclosuresNo relevant conflicts of interest to declare.

Dynamics of Telomere Length Reflect the Clonal Suppression Seen with the Telomerase Inhibitor Imetelstat in Patients with Essential Thrombocythemia

Dynamics of Telomere Length Reflect the Clonal Suppression Seen with the Telomerase Inhibitor Imetelstat in Patients with Essential Thrombocythemia

JAK2V617F Clonal Architecture in MPNs during JAK2 Inhibitor Treatment

IntroductionThe Myeloproliferative Neoplasms (MPNs) are characterized by a recurrent point mutation of JAK2 gene (JAK2 V617F). This mutation, which usually affects only one of the JAK2 gene alleles in Essential Thrombocythemia (ET), frequently becomes homozygous in Polycythemia Vera (PV) and Myelofibrosis (MF) due to homologous mitotic recombination. A JAK2 V617F-mutated disease is strongly associated with a specific constitutional JAK2 haplotype, designated 46/1(GGCC), (Nat Genet 2009; 41:446) with complete linkage disequilibrium although the risk of developing MPNs is independent of the 46/1 haplotype. Furthermore, JAK2 V617F specifically arises on the 46/1 allele in most cases, thus predisposes to the development of MPN (Leukemia 2010; 24:1533; Nat Genet 2009; 41:446). These observations suggest that it is possible to define the JAK 2V617F clonal architecture starting from 46/1 SNP allele burden and the homologous recombination frequency.Aim and Methods The aim of the study was to investigate changes in the JAK2 V617F clonal structure in patients affected by PV, ET or MF and treated with ruxolitinib, a JAK1/JAK2 inhibitor recently approved for MF and PV and under investigation in ET pts intolerant of or resistant to hydroxyurea. We used a recently described methodology (Leukemia 2014;28:460) combining allele burden evaluations of both 46/1 and JAK2 and the frequency of mitotic recombination to derive the percentages of JAK2 V617F clones in MPN patients in 46/1 heterozygous patients for rs12343867 polymorphism (C/T). The JAK2 allele burden values were confirmed independently by two RTQ-PCR methods, according to Lippert (sensitivity, 0.8%) and to Larsen (sensitivity, 0.08%) method.Results We analysed 40 patients (pts) affected by MPNs (12 PV, 1 ET and 27 MF) treated with ruxolitinib over 1 to 5 years (yrs) of follow up (FU); 13 patients (32.5%) presented a reduction of at least 10% of JAK2 V617F allele burden values at latest FU: 7/12 PV (58.3%), 1/1 ET (100%), 6/27 PMF (22.2%). Among these, 9 pts with at least two years of FU were eligible for the study. A quantification of JAK2 homozygous (V617F/V617F), heterozygous (JAK2 V617F/wt) and wild type (wt/wt) clones was obtained using the methodology described above. We found a median reduction of JAK2 V617F/V617F and JAK2 V617F/wt clones of 32.31 % and 8.82 %, respectively, in PV (n.4); 12.22% and 17.86%, respectively, in MF (n.4); 35.99% and 100%, respectively, in ET (n.1). Furthermore, an almost complete molecular remission (CMR) was seen in two PV patients with 4 and 5 yrs of FU respectively and in one ET patient after 5 years of treatment. In these patients we observed reduction of homozygous clones of 99.60%, 86.91% and 100%, respectively, and the residual JAK2 allele burden was due to the persistence of JAK2 V617F/wt clones (Figure). Conversely, in one patients with an increase in JAK2 allele burden from 39% to 45% after 1,5 yrs under ruxolitinib, we observed an increase in JAK2V617F/wt but not in JAK2 V617F/V617F clones.Conclusion. Taken together, these results showed that ruxolitinib may preferentially target the homozygous clones inducing in some cases an almost complete molecular remission with prolonged treatment. Future analysis will be performed to study the clonal architecture in an increased number of patients treated with JAK inhibitors as single agent or in combination with other drugs. [Display omitted] DisclosuresVannucchi:Shire: Speakers Bureau; Novartis Pharmaceuticals Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Baxalta: Membership on an entity's Board of Directors or advisory committees.

Long Term Follow up of a Phase 2 Study of Ruxolitinib in Patients with Splanchnic Vein Thrombosis Associated with Myeloproliferative Neoplasm

Long Term Follow up of a Phase 2 Study of Ruxolitinib in Patients with Splanchnic Vein Thrombosis Associated with Myeloproliferative Neoplasm

Ph-Negative Chronic Myeloproliferative Neoplasms – Population Analysis, a Single Center 10-years’ Experience

Objectives and background. Nowadays chronic myeloproliferative neoplasms (MPN) other than chronic myelogenous leukemia undergo renaissance of interest. It results from advances in decryption of molecular mechanisms of pathogenesis and invention of target drugs. Epidemiological information is needed to assess potential effect and additional costs of new diagnostic and therapeutic techniques. The objective of our study was to review experience of MPN diagnostic and treatment in our center for past ten years.Methods. Our institution serves as primary hematological outpatient department for a half of Saint-Petersburg city with about 2 million inhabitants. We reviewed patients’ charts to obtain information about incidence, symptoms, diagnostic test results, treatment options and relationship to prognostic factors. Statistical methods included descriptive statistics, nonparametric ANOVA for frequencies comparisons and Kaplan-Meyer method with log-rank test for survival comparisons in Statistica 7.0 package.Results. Since 2004 to 2013 there were 570 newly diagnosed MPN patients (pts) in our center. This group consisted of primary myelofibrosis (PMF) (203 pts; 126 female, 77 male; median age 63 years, range 16-83 years), essential thrombocythemia (ET) (201 pts; 146 female, 55 male; median age 58 years, range 23-78 years), polycythemia vera (PV) (166 pts; 96 female, 70 male; median age 57 years, range 20-85 years).The incidence rates were stable during study period: PMF incidence varied from 0.65 to 1.35 with mean of 1.01 new patient per 100 000 inhabitants per year; ET had incidence from 0.60 to 2.1 with mean of 1.00 and PV had incidence from 0.5 to 1.15 with mean of 0.83. The most prevalent symptoms of disease were: splenomegaly (65.5%), constitutional symptoms (fever, night sweats, weight loss) (31.0%), anemia (36.3%) thrombosis (24.1%) for PMF; fatigue (33.2%), headache and dizziness (25.6%), arthralgia (21.8%), erythromelalgia (15.8%) for ET; plethora (82.5%), headache and dizziness (52.4%), fatigue (31.3%) for PV. JAK2V617F was detected in 49.7% of PMF pts, 57.8% of ET pts and in 97.7% of PV pts. Thrombosis rates according WHO IPSET-thrombosis system risks‘ groups of ET and PV pts were: low-risk group 3.33% (3/90), intermediate-risk group 11.1% (13/117) and 39.4% (63/160) in high-risk group with highly significant (p<0.0001) differences between risks’ groups. There were 169 lethal outcomes in the analysed group (102 PMF; 31 ET; 36 PV). Ten-years overall survival rates were 49.8% in PMF pts, 84.6% in ET pts and 78.3% in PV pts. (fig.1). Overall survival in PMF was significantly influenced by risk stratification as IPSS, DIPSS and DIPSS+. Survival curves according DIPSS+ groups are presented in fig.1.Conclusions. Patients with MPN are presented in substantial number; therefore need much finance for novel therapy introduction. Risk stratification systems has high predictive value. Innovative drugs treatment results should be evaluated in comparison with historical control. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

JAK2V617F Complete Molecular Remission in Long-Term Follow-up of Patients with Polycythemia Vera and Essential Thrombocythemia Treated with Ruxolitinib

Polycythemia vera (PV) and essential thrombocythemia (ET) are myeloproliferative neoplasms (MPN) characterized by the presence of JAK2V617F mutation in >95% and 60% of patients (pts), respectively. This mutation usually affects one allele in ET while most PV pts are homozygous due to mitotic recombination. Acquisition of the JAK2V617F mutation is strongly associated with the germline 46/1 predisposition haplotype. Ruxolitinib is a JAK1/JAK2 inhibitor recently approved for myelofibrosis (MF) and under investigation in PV and ET pts intolerant or resistant to hydroxyurea. We enrolled 24 pts, 11 with PV and 13 with ET, in the phase II INCB18424-256 trial that overall included 34 PV and 39 ET pts. 21/24 pts were still on treatment at 5 years (yr), of which 19 JAK2V617F mutated. Results of the PV cohort have been reported recently (Verstovsek et al. Cancer, 2014): with a median follow up of 35 months (mo), the JAK2V617F allele burden decreased by a mean of 8%, 14%, and 22%, respectively, after 12, 24 and 36 mo. The proportion of pts who achieved a reduction ≥50 % at any time during the 1st yr, 2nd yr, and 3rd yr were 5.9%, 14.7%, and 23.5%, respectively, but no patients achieved a complete remission. In our series of pts we evaluated the JAK2V617F allele burden by two RTQ-PCR methods, according to Lippert (sensitivity, 0.8%) and to Larsen (sensitivity, 0.08%) method. We also analysed by next generation sequencing (NGS; Ion Torrent platform) a series of MPN-associated mutations including TET2, ASXL1, IDH1/2, LNK, CBL, SRSF2, EZH2 and MPL at baseline and at 5 yr of treatment in ruxolitinib treated pts who achieved a >25% JAK2V617F allele burden reduction at 5 yr (n=13/19). JAK2V617F allele burden decreased by a mean of 7%, 11%, and 19% at 12, 24 and 36 mo, and decreased further by a mean of 28% after 60 mo. Three (1 PV, 2 ET) of 19 pts (16%) achieved a 50% or greater allele burden reduction after 2 yr; no additional pts achieved this degree of allele burden reduction even in prolonged follow up. These 3 pts further improved their molecular response to a complete molecular response (CMR) after 5 yr of treatment. Their mean JAK2V617F allele burden was 46.6% at baseline, 28.3%, 16.3%, 8.7% and 0% after 1 yr, 2 yr, 3 yr and 5 yr, respectively. The JAK2 CMR was confirmed in at least one independent sample at 3 mo after first discovery. At this last timepoint, the PV pt was in complete haematological remission according to ELN criteria, the 2 ET pts were in partial remission due to platelet count still >400x109/L: 422x109/L and 812x109/L, respectively. BM histopathology in the 2 ET pts at 5 yr, while they were in CMR, showed still evidence of megakaryocyte hyperplasia. In the PV pt, histopathology at 5 yr is pending; evaluation at 3 yr, a time when she was in complete hematologic remission and JAK allele burden had decreased from 69 to 8%, showed normalization of cellularity, megakaryocyte and myeloid lineage compared to baseline but still slight erythroid hyperplasia. All 3 pts had normal karyotype at baseline that remained unchanged thereafter. CMR for JAK2V617F was confirmed by NGS. The 2 ET pts achieving CMR did not show any additional mutations, while the PV pts presented a TET2 Y867H mutation with an allele burden of 48.9% and 52%, respectively at baseline and 5 yr. No recurrent mutations in genes other than JAK2 were found in all other examined cases at baseline or at 5 yr. In 3 informative pts, we also analysed the proportion of JAK2V617F homozygous, heterozygous and wild type clones by the method of Hasan et al (Leukemia 2013) based on allelic discrimination of 46/1 haplotype and JAK2. We found that JAK2V617F/V617F clones were reduced by a mean of 95.5%, JAK2V617F/WT showed an uneven trend with a mean reduction of 45.54% while JAK2WT/WT conversely increased (mean 61.43%) at 5 yr, suggesting that in a subset a patients who present significant reduction of VF allele burden ruxolitinib may preferentially target the homozygous clones. Until now, complete molecular remission in PV pts has been described only in patients treated with interferon. Our data suggest that a subset of pts who present a rapid and sustained reduction of the JAK2V617F allele burden under ruxolitinib may eventually reach a condition of CMR with prolonged treatment. However, similar to findings with interferon, mutations establishing clonality, such as in TET2, may still persist in patients who eventually show the disappearance of JAK2V617F mutated subclones. DisclosuresVerstovsek:Incyte: Research Funding. Vannucchi:Novartis: Membership on an entity’s Board of Directors or advisory committees, Research Funding.

Splanchnic Vein Thrombosis Associated with Myeloproliferative Neoplasms: A Study of the AGIMM & IWG-MRT Groups in 519 Subjects

Philadelphia-negative Myeloproliferative Neoplasms (MPN), including Polycythemia Vera (PV), Essential Thrombocythemia (ET), Myelofibrosis (Primary [PMF] and secondary to PV and ET [PPV-, PET-MF] and unclassified MPN (U-MPN), are associated with an increased risk of venous thrombosis in unusual sites, such as splanchnic vessels (SVT). SVT can lead to complications such as portal hypertension, esophageal and gastric varices, ascites,hepatic failure and biliopathy. According to a meta-analysis MPN is the underlying cause of portal vein thrombosis (PVT) in 31.5% and Budd Chiari syndrome (BCS) in 40.9% of cases (Smalberg, 2012); a more in-depth analysis of clinical characteristics and evolution of MPN-associated SVT has been hampered by heterogeneity of cohorts comprising small number of cases. We conducted a retrospective multicenter study in patients (pts) with SVT associated with WHO2008-diagnosed MPN, with the aim to describe patient characteristics, disease course and prognostic factors with potential implications for clinical practice. Data were collected from 16 international hematologic centers in the framework of the Italian AGIMM and the IWG-MRT groups. We collected 519 cases of pts with PVT, splenic or mesenteric vein thrombosis (75.1%) and BCS (24.9%) associated with MPN. We used as comparator a cohort of 1686 controls (Ctr) represented by MPN without (w/o) SVT: 741 ET (43.9%), 684 PV (39.7%), 261 PMF (15.5%). Frequency of MPN associated with SVT was 37.8% ET (n=196), 36.8% PV (n=191), 15.4% MF (n=80), 10% U-MPN (n=52). Median follow-up was 89.9 months (mo) (range 0.5-430). For SVT vs Ctr group females were 54.5% vs 44.4% in PV (P=0.001), 68.4 vs 63.5% (p=0.13) in ET, 63.7% vs 29.1% in PMF (p<0.0001); median age at MPN diagnosis (dg) was 43.5 yr (range 12-90) vs 60.6 yr (range 12-93) (p<0.0001). Age at SVT dg was 44 yr (range 15-85). In 240 cases (46.7%) MPN and SVT dg were coincident, in 121 (23.6%) SVT occurred before MPN dg (median 26 mo, range 4-307) and in 153 (29.8%) during MPN follow up (median 68 mo, range 4-362). JAK2V617F mutation was found in 94% PV vs 94% in Ctr, 84% vs 61% ET (p<0.0001), 88.1% vs 68% PMF (p=0.006) and in 93% U-MPN. Erythropoietin-independent colonies (EEC) were evaluated in 111 SVT pts and found in 80 (72%), accounting for 38/48 PV (79%), 31/44 ET (70.5%), 9/12 PMF (75%) and 2/7 U-MPN (28.6%). At dg, SVT PV pts had lower hemoglobin levels than Ctr: median was 17.4 g/dL vs 18.5 g/dL (p<0.0001) in male, 16.9 g/dL vs 17.7 g/dL (p=0.0006) in female. A co-existing thrombophilic status was found in 38.5% SVT vs 11.8% of Ctr (p<0.0001). Recurrent SVT occurred in 12.2% of pts with a rate of 1.6% person/year (CI 1.2-2.1); risk of venous thrombosis other than SVT was increased in SVT group vs Ctr (p=0.02), with no difference for arterial thrombosis. Hemorrhage was more frequent in SVT group (32%) vs Ctr (7.2%)(p<0.0001), mainly related to esophageal varices, which were present in 66.9% of SVT pts. There was no difference in evolution to MF and acute leukemia (AL) for PV and ET pts with and w/o SVT, while risk of AL was lower in MF with SVT (p<0.00001). Overall survival was shorter in ET pts with SVT vs Ctr (p<0.0001). In PMF survival was better in SVT group (p<0.00001) and was associated with a higher proportion of SVT pts in lowest risk categories: IPSS low 65%, intermediate-1 20%, intermediate-2 10% and high 5% compared with 15%, 34%, 25% and 26% in Ctr group. At last FU, 79/519 pts (15.2%) had died; causes of death were evolution to AL (15.4%), other cancers (13.8%), disease progression without AL (10.8%), SVT (10.8%), hepatic failure and venous thrombosis other than SVT (7.7% each), heart failure and arterial thrombosis (6.2% each), hemorrhage (5.5%), renal failure and infection (4.6% each). Therapy after SVT included anticoagulation in 77%, antiaggregant in 21.2% and combination in 1.8%; 70% received cytotoxic drugs; 12.4% were treated with transjugular porto-systemic shunt. Beta blocker therapy was used in 48.5% of pts and correlated with improved survival (p=0.041) MPN associated with SVT correlated with younger age and female sex and might antedate the clinical phenotype in a quarter of the patients. MPN-associated SVT equally affected PV and ET, was more likely to occur in the presence of JAK2V617F or underlying thrombophilia and predicted recurrent venous but not arterial thrombosis. The apparent association of SVT with better or worse prognosis in PMF and ET, respectively, requires further investigation. DisclosuresNo relevant conflicts of interest to declare.