Essential Thrombocythemia Research Articles

Marrow Hypercellularity Does Not Exclude the Diagnosis of Essential Thrombocythemia (ET)

Background: The 2022 WHO criteria do not list bone marrow cellularity as a criterion for ET diagnosis (dx) 1, but a review discussing the International Consensus Classification criteria states that the marrow should be normocellular for age, with rare cases of mild hypercellularity 2. The ELN also cited normocellularity as a key factor in differentiating ET from polycythemia vera (PV) or prefibrotic myelofibrosis (MF), further suggesting that normocellularity is the expected standard in ET 3. However, we encountered a number of cases in our hematology practice with increased cellularity in bona fide ET patients (pts). Therefore, we decided to more systematically review the marrow cellularity and its prognostic impact. Methods: Medical records were queried for pts with ET per the ICD, versions 9-10. The dx of ET per WHO 2022 was confirmed by manual review. Cases lacking marrow biopsy were excluded. Structured query language was used for automated extraction of clinical, lab, and molecular findings. We utilized our previously described natural language processing pipeline to extract cellularity information from marrow reports 4. All hematopathology reports of hypercellular marrows were manually reviewed by 3 observers for confirmation and a randomly selected subset of the core and clot sections were reviewed for histomorphology and cellularity by 2 expert hematopathologists and 1 histomorphologist, blinded to pt age and clinical information prior to their review. Quantitative cellularity was determined independently and then congruently for consensus. Qualitative cellularity was defined using (100-age) ± 20% as the normal range with increases above this range considered hypercellular for age. Disease progression was defined as either progression to post-ET MF (PETMF) or direct transformation to acute myeloid leukemia. Transformation to PV was defined as pts with a JAK2 mutation for whom PV was thoroughly excluded at the time of ET dx but who developed absolute erythrocytosis and met the PV WHO diagnostic criteria later in their disease course. We performed univariable and multivariable analysis of progression, PV transformation, thrombosis and mortality risk using Cox proportional-hazards models. Overall (OS), progression-free (PFS), PV-free (PVFS) and thrombosis-free (TFS) survival were estimated using Kaplan-Meier methods. Results: 382 pts met WHO defined ET with marrow dx, of which 145 had pre-treatment diagnostic marrows available for review at Weill Cornell. In the other 237, the diagnostic biopsies had either been performed after treatment was initiated or only the report was available. Thirty-three (23%) were described as hypercellular and 112 (67%) were not. Review of 20 randomly selected marrows from the hypercellular group confirmed age-adjusted hypercellularity ranging from 30 to 80%. The hypercellular pts were significantly older at dx compared to those without hypercellularity (59 vs 50 yrs, p <0.001, Table 1). We identified no other significant differences in blood counts at dx, sex, driver mutation or thrombosis history between the groups. Univariate and multivariate analyses demonstrated no significant difference between the groups in PFS (HR 1.29, p=0.871), TFS (HR 1.39, p=0.671) or OS (HR 0.50, p=0.487) using age, thrombosis history and sex as covariates. A Cox model could not be generated for PVFS due to the low number of events. The 15-year PFS for pts with hypercellularity vs those without was 97% and 94% respectively ( p=0.56, Figure 1), 15-year PVFS was 100% and 67% respectively ( p=0.12), 15-year TFS was 79% and 87% respectively ( p=0.53) and 15-year OS was 84% and 81% respectively ( p=0.74). Conclusion: Our data to date suggests that hypercellularity is of importance diagnostically but not prognostically. Nearly a quarter of our pts with WHO ET had marrow that was hypercellular for age at dx. Pts with increased marrow cellularity tended to be older but were clinically indistinguishable from the remainder in terms of driver mutation, blood counts and thrombosis history. Univariate and multivariate analyses demonstrate that hypercellularity does not confer increased risk of progression, thrombosis or mortality. Thus, hypercellularity alone should not be used as a factor for excluding ET dx.

Clinical Study of Lymphocyte Subsets in Patients with BCR/ABL Negative Myeloproliferative Neoplasms

Background Myeloproliferative neoplasms (MPNs) are stem cell-derived clonal myeloid malignancies characterized by abnormal proliferation of one or more lineages of myeloid cells in the bone marrow resulting in varying degrees of increase in peripheral blood cells.BCR-ABL-negative MPN mainly include essential thrombocythemia (ET), polycythemia vera (PV) and myelofibrosis (MF). It is still unclear that the pathogenesis of MPN,but a large number of studies have shown that MPN has abnormalities in the immune microenvironment. Aiming to investigate the potential contribution of lymphocyte subsets to the pathogenesis of MPN, we investigated the peripheral blood lymphocyte subsets in MPN patients with different clinical characteristics. Methods A total of 123 patients (57 ET, 17 PV and 49 PMF) with MPN admitted to the First Affiliated Hospital of Nanchang University from October 2020 to February 2023 were retrospectively studied. Dynamic data of lymphocyte subsets were collected. The levels of peripheral lymphocyte subsets were measured by flow cytometry before treatment, and their association with clinical characteristics was analyzed. Results: Among 123 patients with MPN，57 patients were diagnosed with ET with a median age of 62 years (range, 20-86), 17 patients were diagnosed with PV with a median age of 53 years (range, 19-70), 49 patients were diagnosed with PMF with a median age of 63 years (range, 26-81). 55 patients had varying degrees of splenomegaly, of which 14 (24.6%) patients with ET, 32 (65.3%) patients with PMF, and 9 (52.9%) patients with PV. Further comparing the incidence of splenomegaly in patients with ET, PV and PMF, it was found that the incidence of splenomegaly with PMF and PV was significantly higher than ET patients. There were significant differences in lymphocyte subsets counts in MPN patients compared to controls. We found that CD3+ T-cell counts, CD3+CD8+ T-cell counts, CD16+CD56+ NK-cell counts, CD19+CD3-B-cell counts, and Treg counts were reduced in patients in the MPN group in comparison to controls.And patients with PMF have reduced CD3+ T-cell counts, CD4+ T-cell counts and Terg-cell counts compared to ET patients. In different driver mutations patients we find that with CALR mutation had significantly lower CD16+CD56+ NK cell counts compared to controls,JAK2V617F mutation had significantly lower CD3 +T cell counts, CD3 +CD4 +T cell counts, CD3 +CD8 +T cell counts, CD16 +CD56 +NK cell counts, CD19 +CD3 -B cell counts compared to controls,triple negative patients had significantly lower CD3 +T cell counts, CD8 +T cell counts, CD16 +CD56 + NK cell counts compared to controls. Different clinical presentations have different immune characteristics.Patients with ET who develop splenomegaly show decreased CD8+ T cell counts compared to non- splenomegaly patients. We did not obtain similar findings in splenomegaly patients with ET and PV.Overt-PMF patients had lower of CD3+ T cell counts, CD4+ T cell counts, CD8+ T cell counts, Treg cell counts compared to pre-PMF patients. Conclusion PMF patients having more impaired immune function than ET and PV patients. Immune function was impaired differently in MPN patients with different driver mutations, The immune function of JAK2V617F mutations and triple-negative patients is more severely impaired than CALR mutated patients. Patients with splenomegaly, and overt-PMF patients have more impaired immune function.This is also consistent with the prognostic differences between the different clinical characteristics of MPN.

Progression to Myelofibrosis in Patients with Essential Thrombocythemia: A Real-World Analysis from the Prospective MOST Study

Background: Essential thrombocythemia (ET) is a myeloproliferative neoplasm (MPN) characterized by clonal blood cell proliferation, excessive platelet production, constitutional symptoms, and increased risk of vascular complications, as well as a risk of progression to myelofibrosis (MF). Previous prognostic studies of patients with ET have largely been based on retrospective analyses, and limited prospective data exist regarding disease progression. The prospective Myelofibrosis and Essential Thrombocythemia Observational Study (MOST) collected real-world data from patients with ET. This analysis evaluates disease progression in patients with ET enrolled in MOST. Methods: MOST (NCT02953704) enrolled patients with ET aged ≥60 years, or with a history of thromboembolic events, or who were receiving ET-directed therapy (excluding aspirin only). Baseline clinical characteristics data were collected as previously described (Yacoub A. CLML. 2021). For this analysis, progression from ET to MF was defined as meeting 1 or more of the following criteria during the study period: 1) Bone marrow biopsy with fibrosis grade ≥2 or pathologic diagnosis of MF; 2) death owing to MF/myelodysplastic syndrome/acute myeloid leukemia; 3) circulating blasts >1% and new/worsening splenomegaly (SPM); 4)new/worsening SPM and ≥2 of white blood cell (WBC) count >11×10 9/L, hemoglobin (Hb) <10 g/dL, and platelet count <100×10 9/L. Median (range) follow-up was 57.3 months (42-70). Results: Of the 1237 patients with ET enrolled in MOST; 53 (4.3%) met criteria for progression to MF. Among patients with progression, most had progressed due to fibrosis (criteria 1, 56.6%); 15.1%, 11.3%, and 28.3% of patients progressed due to criteria 2, 3, and 4, respectively. Notably, only 176 patients (14.2%) enrolled in the study had bone marrow data available. Comparison of the enrollment characteristics of patients with and without progression identified no differences in age at enrollment or diagnosis (Table 1). However, time from diagnosis to enrollment and from diagnosis to end of study were significantly longer in patients with progression than those without (median 7.9 vs 4.2 years, median 12.7 vs 9.0 years, respectively; both P=0.001). Of all enrolled patients with vs without progression tested for known driver mutations, a higher percentage with progression were JAK2-positive vs those without progression (80.6% [29/36] vs 69.7% [598/858]). At enrollment, the percentages of patients with vs without progression receiving ET-directed therapies were similar (94.3% vs 94.8%). Among patients with vs without progression, mean baseline Hb was significantly lower (12.5 g/dL vs 13.1 g/dL; P=0.026), mean WBC counts were significantly higher (10.4×10 9/L vs 7.4×10 9/L; P<0.001), and mean platelet counts were comparable (418.6×10 9/L vs 455.0×10 9/L; P=0.466). MPN-SAF TSS was similar for patients with vs without progression at baseline. Fewer patients with vs without progression had ≥1 thrombotic events (1.9% [1/53] vs 3.7% [44/1184]) during the study, whereas a higher percentage of patients had ≥1 hemorrhagic events (7.5% [4/53] vs 1.3% [15/1184]). Conclusions: This real-world analysis of data from MOST showed that 4.3% of patients with ET progressed to MF during the study period. Compared with patients without progression, patients with ET to MF progression had longer duration of disease, higher WBC count, and lower Hb at enrollment; symptom burden at enrollment was similar between the 2 groups. One limitation of this study is the lack of bone marrow data for the majority of patients, suggesting a possible underestimation of progression to MF. These findings and further analysis of MOST data will add insight into disease progression in patients with ET and facilitate clinical management of this patient population.

Clinical and Disease Characteristics of Patients with Myelofibrosis and Essential Thrombocythemia Who Harbor a Calreticulin (CALR) Gene Mutation: Subanalysis of the MOST Study

Background: Calreticulin(CALR)gene mutations are the second most frequent driver of disease in myelofibrosis (MF) and essential thrombocythemia (ET). Compared with patients with JAK2 mutations, those with CALR mutations are considered to have lower-risk disease; however, prospective data on clinical characteristics and disease progression for patients with CALR mutations are limited. This study compared the disease characteristics and treatment patterns of patients with MF or ET who had CALR mutations vs those who had JAK2 mutations at enrollment in the Myelofibrosis and Essential Thrombocythemia Observational Study (MOST; NCT02953704). Methods: Patients enrolled in MOST were aged≥18 years with clinical diagnoses of MF or ET at clinical practices within the United States. Patients with MF included those with primary or secondary MF who were low risk (or intermediate-1 by age >65 years alone) per the Dynamic International Prognostic Scoring System (Passamonti F, et al. Blood. 2010;115:1703-1708). Patients in the ET cohort had a clinical diagnosis of ET and were ≥60 years or had history of thromboembolic events or were receiving ET-directed therapy at enrollment. Descriptive statistics were used to summarize the data. The median (range) follow-up time for CALR- and JAK2-positive patients was 52.8 (43-68) months and 56.6 (42-70) months, respectively. ET progression was defined as transformation to MF; MF progression was defined as worsening of objective clinical and laboratory assessments of disease. Results: A total of 881 patients ( CALR-positive, n=137 [16%]; JAK2-positive, n=750 [85%]; 6 patients had both CALR and JAK2 mutations) were included in this study. A summary of patient and disease characteristics are presented in Table 1 and Table 2. At enrollment, 25% and 75% of CALR-positive patients had a diagnosis of MF and ET, respectively, vs 16% and 84% of JAK2-positive patients. The majority of patients in both groups were women ( CALR-positive, 56%; JAK2-positive, 65%). CALR-positive patients were younger at enrollment and at diagnosis compared with JAK2-positive patients (median age at enrollment, 63.0 [24.0-89.0] vs 70.0 [26.0-93.0] years, P<0.001; median age at diagnosis, 59.3 [21.0-87.0] vs 66.3 [22.0-93.0] years, P<0.001). The majority of patients in this analysis (79% of CALR-positive, 90% of JAK2-positive) were receiving MPN-directed therapy at enrollment. The most common therapies in the CALR cohort were hydroxyurea (51%), interferon (12%), and anagrelide (8%); the common therapies among patients in the JAK2 cohort were hydroxyurea (66%), aspirin only (10%), and ruxolitinib (8%). Disease burden at enrollment was also assessed. The percentages of patients with white blood cell (WBC) count >10×10 9/L or platelet count >400×10 9/L were similar for both CALR- and JAK2-positive patients (13% vs 20% and 53% vs 51%, respectively). Percentages of patients with splenomegaly (SPM) were similar for CALR- vs JAK2-positive patients at enrollment (11.0% vs 13%). The mean MPN-SAF TSS was similar at baseline for CALR- and JAK2-positive patients (15.1 vs 16.5). The percentage of patients with MPN-SAF TSS >25 was 12% in the CALR-positive and 16% in JAK2-positive cohorts. Disease complications and progression were also assessed. Thrombotic and hemorrhagic events during the study period were infrequent in both CALR- and JAK2-positive patients (2% vs 4% and 1% vs 3%, respectively). Rates of disease progression were similar for CALR- and JAK2-positive patients, both for MF progression (50% vs 61%) and for ET progression to MF (2% vs 5%). Leukemic transformation occurred in 6 (4%) CALR-positive patients and 43 (6%) JAK2-positive patients. Deaths due to disease progression occurred in no CALR-positive patients and in 18 (2%) JAK2-positive patients. Conclusions: The results of this real-world analysis of the MOST study demonstrate that despite nearly 80% of CALR-positive patients receiving MPN-directed treatment, a substantial percentage of this group did not meet treatment goals, including control of symptom burden, WBC and platelet counts, and SPM. In addition, disease progression was observed in 50% of the patients with MF in the CALR-positive cohort. Further analysis of the MOST study may provide insight into optimal management of patients with CALR mutations.

Do Hematologic Parameters Predict Thrombosis or Disease Transformation in Essential Thrombocythemia?

Background: Patients with essential thrombocythemia (ET) are burdened with an increased risk of thrombosis and disease transformation, both significant contributors to morbidity and mortality. However, based on the available literature, there are limited tools available to predict the development of these complications. Particularly, the association between hematologic parameters and thrombosis is unclear, making risk stratification and disease management challenging. Utilizing a large retrospective database, we assessed the impact of hematocrit (Hct), red blood cell count (RBC), white blood cell count (WBC), and platelet count (Plt) on the subsequent development of thrombosis and disease transformation to myelofibrosis (MF), polycythemia vera (PV), and acute leukemia. Methods: We included ET patients treated at our institution between 2007 and 2021. The index time was date of diagnosis or date of first contact at Mount Sinai Hospital for patients with a prior history of ET. Hematologic parameters (Hct, RBC, WBC, Plt) were documented at three-month intervals after the index time. Patients were included in the study if they had at least three sets of laboratory values prior to the outcome of interest. For each hematologic parameter, we performed univariate cox analysis of time to thrombosis or progression to either MF, PV, or acute leukemia. Each lab parameter was analyzed as a time dependent covariate, taking into account the length of time the patient was above or below the threshold of interest. Hct and plt were specifically evaluated as dichotomous variables, with a cut off of less than or greater than 45% for Hct based on CYTO-PV results. For plt, two cut-off values were used: less than or greater than 400 (based on ELN response criteria) and less than or greater than 600 (based on Cortelazzo et al HU treatment goal) in plt/microliter. Results: We identified 430 patients who met criteria and were included in the analysis. Our cohort of patients was mostly female (61%), non-Hispanic (66%), white (64%), JAK2 mutated (60%), with an average age at diagnosis of 56 years and a median follow-up time of 33 months. 41 (7%) patients had a history of prior thrombosis. There was a total of 23 major thromboses that occurred after the index time with 12 venous and 11 arterial thrombotic events. 38 patients progressed to post ET-MF, 20 patients developed post ET-PV, and 10 patients transformed to acute leukemia. For the assessment of thrombotic risk, there were no significant associations between any of the hematologic parameters and this outcome. We also evaluated the risk of thrombosis in the JAK2 positive subset of patients (n of 15), and did not find any significant association with any of the lab parameters (in particular, for hct < 45%, p > 0.99). For transformation to MF, plt < 400 x10 9/L was associated with an increased risk of the development of post-ET MF (HR 2.2, p 0.016), and the same was seen with plt < 600 x10 9/L (HR 2.2, p 0.044). The development of PV was less likely with a hct lower than 45% (HR 0.03, p < 0.001), with similar results seen for plt < 400 x10 9/L (HR 0.2, p 0.03) and plt < 600 x10 9/L (HR 0.2, p 0.002). For transformation to acute leukemia, plt < 400 x10 9/L (HR 8.3, p 0.008) was associated with an increased risk of this complication. Conclusions: In this retrospective cohort of 430 patients with ET, we found no associations between four different hematologic parameters over time with thromboses. In particular, this data once again argues against aiming to achieve a particular platelet goal to minimize thrombosis in ET patients. The lack of association between hematologic parameters and thrombotic risk was similarly exemplified in our subset of JAK2 mutated ET patients. Pertaining to disease transformation, plt count appeared to be the most predictive out of all of the parameters, with lower plt values corresponding to increased risk of both post-ET MF and acute leukemia, which both warrant further exploration. A hct level of less than 45% appeared to be protective against the development of post-ET PV. Significant limitations of our study include the retrospective nature as well as the small number of events of interest that our patients experienced. Future studies must continue to focus on surrogate endpoint validation in order to more reliably predict thrombotic events as well as disease progression in patients with ET given the significant morbidity and mortality that such events incur.

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.

Myelofibrosis Is Associated with Poor Cardiovascular Outcomes after Heart Failure Hospitalization

Background: Myeloproliferative neoplasms (MPN), including essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF), are at high risk of cardiovascular (CV) disease including heart failure (HF). Prior studies have suggested patients with MPN are at increased risk of HF. Among patients with MPN, those with MF have the most aggressive disease with significantly shortened survival. However, data on CV outcomes among patients with MF are sparse. Therefore, we examined CV outcomes among patients with MPN hospitalized for HF. Methods: This was a retrospective cohort analysis of the National Readmission Database (NRD) of adult patients with a primary diagnosis of HF from 2017 and 2018 with a history of MPN (N = 4632), which were identified using ICD-10 codes. The primary outcome was 90-day unplanned CV-related readmission (readmission for HF, arterial thrombotic event [ATE], or venous thromboembolism [VTE]). Secondary outcomes were index hospitalization death and 90-day any-cause unplanned readmission. Propensity scores (PS) for estimating probability of MF were calculated using non-parsimonious multivariable logistic regression that included all baseline patient characteristics examined. PS weighting (PSW) was utilized to adjust for potential confounders. Patients with MF were compared with patients with ET or PV and standardized mean difference (SMD) was calculated for variables before and after PSW. Imbalances between groups were significant if SMD for a given covariable was ≥ 0.10. Hazard ratios (HR) were estimated for 90-day readmission outcomes using Cox proportional hazards regression and odds ratio (OR) for estimating index hospitalization death were calculated using logistic regression. Results: A total of 3748 patients with ET or PV (2639 ET, 1109 PV) and 884 with MF were included. Prior to PSW, patients with MF were older (mean age 77.7 vs 74.3 years), more likely to have anemia (53.8% vs 47.2%) and less likely to be female (44.9% vs 56.1%), have systolic HF (39.9% vs 46.1%), and cardiogenic shock (1.6% vs 3.4%) compared with ET/PV, Table. After PSW, baseline characteristics were well balanced between groups. After PSW, MF was associated with increased risk of 90-day CV readmission (HR 1.18, 95% CI 1.08 - 1.30), index hospitalization death (OR 1.67, 95% CI 1.38 - 2.01), and 90-day any-cause readmission (HR 1.26, 95% CI 1.17 - 1.35). Additionally, MF was associated with increased risk of 90-day HF readmission (HR 1.24, 95% CI 1.12 - 1.38) but not ATE (HR 0.62, 95% CI 0.47 - 0.81) or VTE-readmission (HR 0.72, 95% CI 0.43 - 1.19), Figure. Conclusions: Patients with MPN admitted with HF have high rates of 90-day CV-related and any-cause readmissions. MF was associated with higher risk of 90-day CV-related, HF, and any-cause readmission compared with patients with ET or PV. Patients with MF had higher risk of index HF hospitalization mortality compared with ET or PV. More investigation is needed in order to identify risk factors for adverse CV outcomes in patients with MPNs with HF, particularly those with MF. Although preventing thrombotic complications and managing CV risk are part of routine care for ET and PV patients, this study highlights the importance of incorporating CV risk management in MF patients.

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.

An Innovative Dynamic Nomogram for Stratifying Survival Prognosis in Essential Thrombocythemia Patients with a History of Thrombosis

Background:Essential thrombocythemia (ET) with a previous history of thrombosis was classified as high risk according to the revised International Prognostic Score for Thrombosis in ET. However, prognostic factors are not well established in this patient population. With the aim of enhancing patient outcomes, we endeavored to develop a prognostic nomogram specifically for patients with ET and a prior history of thrombosis. Methods:We included 318 ET with previous arterial or venous thrombosis or both from January 2008 to June 2022 in our study. We used multivariable Cox proportional hazards regression to build a dynamic prognostic nomogram for this patient population. Harrell C Index was used for nomogram discrimination. Internal validation was performed by bootstrap resampling. The area under the receiver operating characteristic curve (AUC) was used to determine the nomogram's performance. Results:Based on the IPSET model, out of the 318 patients, 148 were categorized as having an intermediate risk (score of 1-2), while 170 patients were classified as high risk (score greater than or equal to 3). Substantial statistical significance was observed in the overall survival between these two groups, underscoring the ability of the IPSET model to stratify prognosis in essential thrombocythemia patients with a history of thrombosis . We further used multivariable cox regression analysis and found that Age≥60 years (HR=5.68 [95% CI:1.44-22.47], p=0.013), splenomegaly (HR=5.66 [95% CI:1.74-18.43], p=0.004), abnormal karyotype (HR=5.28 [95% CI:1.38-20.25], p=0.015), white blood cell counts (HR=1.09 [95% CI:1.02-1.18], p=0.014), and hemoglobin (Hb, HR=0.97 [95% CI:0.95-0.99], p=0.006) were independently risk factors for survival. We created a nomogram as well as a web portal that enables survival predictions based on individualized parameters ( https://cae29l-jia-chen.shinyapps.io/DynNomapp/ ). The C Index of the nomogram was 0.818. The AUC of 3-year, 5-year, and 10-year survival of the nomogram were 0.854, 0.769, and 0.813, respectively. Sex biases were observed at Hb levels that contribute outcome heterogeneity in such ET patients. Conclusions : We provided a new dynamic nomogram that can well evaluate the survival prognostication for a given ET patient with a previous history of thrombosis, with a good discrimination and excellent performance.

Impact of Kidney Dysfunction on Overall Survival in Myeloproliferative Neoplasms: A Single-Center Retrospective Study

Introduction: Myeloproliferative neoplasms (MPN) are clonal hematopoietic stem cell disorders that can lead to the deposition of fibrous tissue, and by a propensity toward extramedullary hematopoiesis. The progression of kidney function and frequency of chronic kidney disease (CKD) in patients with MPN is unknown, although CKD is linked to increased mortality. In our study, we aimed to investigate the relationship between kidney function as measured by glomerular filtration rate (eGFR) and MPN disease and risk of thrombosis. Moreover, we analyzing the risk factors for CKD, impact of different treatment modalities and effect of CKD on survival. Patients & Method: We haveretrospectively screened 762 patients between Jan 1989 to May 2019 with MPN at Princess Margaret Cancer Centre. Diagnosis, of Polycythemia (PV), essential thrombocytosis (ET), and myelofibrosis (MF; comprising PMF, post-ET-PMF, and post-PV-PMF) was required as defined by the WHO classification. Patients with other MPNs (CNL, CEL, HES, MDS/MPN, MPN-U, Mastocytosis accelerating phase MPN and blast phase) or missing serial creatinine measurement or their CKD attributed to other causes (diabetic nephropathy, High blood pressure, polycystic kidney disease obstructive uropathy, Glomerulonephritis before MPN diagnosis and other) were excluded, resulting in study sample of 232 patients. The total cohort was subdivided according to the calculated eGFR, (ml/min/1.73m2) into eGFR1 (≥90, n=154), eGFR2 (60-89, n=12), and eGFR3 (<60, n=66). eGFR was collected retrospectively, because of small number of patients, we combined eGFR2 and eGFR3 in one group. Overall Survival (OS) was calculated using the Kaplan-Meier and log-rank test was used to assess impact variables of interest. Cox proportional hazards model was used to assess for prognostic factors of OS as well as to assess the joint effect of potential prognostic factors. Results: Median age for the total cohort was 58 years (range;18-88.3), 54% were male. Median follow-up duration was 86 months (range:45.5-135). Diagnosis of MPN involved ET; n=21(9%)), PV; n=32 (14%) and MF; n=179 (77%). JAK2V617F status was documented in 219 patients; 67% were positive; of 106 patients analyzed for CARL 40.6% were positive. Cardiovascular risk factors were higher in PV and MF than in ET (59.4%, 57% &38%) respectively. A higher uric acid and LDH levels were found in PV and MF. A total of 19% had a history of thrombosis and rate was higher in ET (28.6%) than PV (21.9%) or MF (16.8%). Further patient's characteristics summarized in Table1. Kidney biopsy performed in 8 patients. The most prominent histological finding included focal segmental glomerulosclerosis (n=3), Ig A nephropathy (n=3), mesangial hypercellularity and sclerosis, extramedullary haematopoiesis (n=1) and lupus nephritis (n=1). The risk factors for CKD based on eGFR group are presented in (Table 2). MPN diagnosis is a significant risk factor for kidney function (p=0.0117). In MF a higher rate of eGFR 88.5% compared with PV and ET. JAK2V617 demonstrates a significant impact on abnormal eGFR (p=0.05);. IPSS and DIPSS score are a significant risk factor for kidney dysfunction (p=0.0014, and 0.0074 respectively). High uric acid levels and neutrophil counts were higher in high eGFR group (p=0.0014, and 0.0074 respectively). No association found between thrombosis and high eGFR. Hydroxyurea treatment does not have an impact on CKD, however, more patients received Ruxolitinb in abnormal eGFR (p=0.001). CKD has significant impact on OS. The 5 years OS for eGFR1 was 75% (95% CI 67%-81%), and for abnormal eGFR was 63.9% (95% CI 52%-73%), p=0004 (Fig 1). Conclusion: Higher incidence of kidney dysfunction associated in MF compared to PV and ET, there was no association between thrombosis and high eGFR as we excluded all other cause of CKD. MF with abnormal eGFR associated with high DIPSS score. MPN patients with kidney dysfunction significantly affects OS, which indicate close monitoring and prospective study is required.

Loss of Heterozygosity of Chromosome 9p and Progression in MPNs

Introduction Copy-neutral loss of heterozygosity (LOH) of chromosome 9p, concomitant with mutated JAK2, can occur in myeloproliferative neoplasms (MPNs), and may be the most common chromosomal aberration in patients with polycythemia vera (PV). The prevalence of LOH of 9p varies amongst the different MPNs and is highest in PV where it has been reported to be between 30-70%. The reported prevalence of LOH of 9p is 20-50% and 10-20% in patients with myelofibrosis (MF) and essential thrombocythemia (ET), respectively. A hallmark feature of MPNs is the tendency to progress to more aggressive disease phenotypes (i.e., PV/ET to MF to accelerated- or blast-phase MPN) through the acquisition or loss of cytogenetic and molecular clonal markers. Although loss of LOH of 9p likely contributes to progression in MPNs, its pathologic role is still incompletely defined. Methods We conducted a retrospective review of patients at a single-center, tertiary-care institution who were diagnosed with an MPN, either chronic, accelerated or blast-phase (MPN-AP/BP), from January 1 st, 2017 until July 1 st, 2023. All patients underwent a microarray-based chromosome analysis using the I Scan System with the Global Diversity Array-8 (GDA) v1.0 Array BeadChip. Mutational profiling was done using the NextGENe software (SoftGenetics LLC) and MiSeq Reporter, and variant annotation and filtration was performed using VarSeq (Golden Helix). Results Fifty-two patients with MF were identified. Twenty-eight patients (53.8%) were found to have LOH of 9p, 15 of whom had secondary MF (7 with preceding ET and 8 with preceding PV). Eight of 9 patients (88.9%) with PV-MF harbored LOH of 9p, vs. 6 of 13 (46.2%) with ET-MF. The median cell fraction affected was 70% (range, 5-95%) and the median JAK2 variant allele frequency (VAF) was 75% (range, 16-97%). Eleven of the 24 patients without LOH of 9p harbored JAK2 mutations, at a median VAF of 40%. Nine patients (32.2%) with LOH of 9p had abnormal cytogenetics by conventional karyotyping, compared to 8 (33.3%) without LOH of 9p. Eleven patients (39.3%) with LOH of 9p were MIPSS-70 v2 high or very high risk, compared to 10 (41.7%) patients without LOH of 9p. Nine patients (32.1%) with LOH of 9p were DIPSS-plus intermediate-2 or high-risk, compared with 9 (37.5%) patients without LOH of 9p. Twenty patients with MPN-AP/BP were identified, of whom 11 had MPN-AP and 9 had MPN-BP. Four patients (20%), all with MPN-BP, had LOH of 9p. Median JAK2 VAF in these patients was 50% (range, 38-80%), vs. 4% (range, 3-48%) in the 6 patients with JAK2 without LOH of 9p. Two of 19 patients (10.5%) with ET were found to have LOH of 9p, with a corresponding JAK2 VAF of 70% and 20%. Twelve of the 17 patients (70.6%) who did not have LOH of 9p had a JAK2 mutation, at a median VAF of 27% (range, 4-44%). One patient with LOH of 9p had a thrombotic event, vs. 4 of 17 patients (23.5%) without LOH of 9p. Three of 9 patients (33%) with PV were found to have a LOH of 9p, with a median corresponding JAK2 VAF of 61% (range, 55-81%). Median JAK2 VAF for the other 6 patients (all with a JAK2 mutation) was 34% (range, 26-46%). One patient with LOH of 9p had a thrombotic event vs. 3 of 6 patients (50%) without LOH of 9p. Discussion The highest prevalence of LOH of 9p in patients with an MPN was seen in those with MF (>50%), followed by PV, MPN-AP/BP and ET. These results are generally in line with those previously reported, though the prevalence in PV was lower than other studies (likely due to small sample size). The prevalence of LOH of 9p in ET-MF was more than four times higher than in ET, suggesting that LOH of 9p may be an acquired cytogenetic aberration involved in ET progression. LOH of 9p was seen in almost 90% of PV-MF vs. 33% of PV patients, further supporting that LOH of 9p may be implicated in MPN progression. Notably, LOH-9p was seen in far fewer patients with accelerated- or blast-phase disease. It is likely that clonal evolution of MPNs to MPN-AP/BP is driven more so by the acquisition of high-risk mutations (e.g., TP53, ASXL1, U2AF1) and less by changes such as LOH of 9p and increased JAK2 VAF. In summary, our data largely confirms previous reports regarding the prevalence of LOH of 9p in MPNs while suggesting a role for the gain or loss of LOH of 9p in the progression of these hematologic cancers.

Exploratory Study on Impact of Comorbid Sleep Apnea Treatment in Patients with Polycythemia Vera and Essential Thrombocythemia

Background: Systemic inflammation has been implicated in the progression of myeloproliferative neoplasms (MPNs), polycythemia vera (PV) and essential thrombocythemia (ET). Obstructive sleep apnea (OSA) is a highly prevalent disorder that can lead to TNF-driven systemic inflammation. OSA leads to oxidative stress and NF-kB driven inflammatory gene expression through the mechanistic pathways of intermittent hypoxia and autonomic activation. We therefore sought to understand the prevalence of OSA in patients with MPNs and the feasibility of understanding the impact of treating comorbid sleep apnea in patients with PV and ET. Methods: Patients with PV and ET diagnosed using the 2008 or 2016 WHO criteria underwent STOP-BANG questionnaires to evaluate for the likelihood of OSA. Based on the finding of 3 or more positive responses on STOP-BANG questionnaire (PLoS One 2015;10:e0143697), patients underwent further evaluation with polysomnography or home sleep apnea test to diagnose OSA at an American Academy of Sleep Medicine-certified sleep laboratory (Figure 1). Patients with apnea-hypopnea index (AHI) of 5 or more events per hour and Eastern Cooperative Oncology Group scale score of 0-2 underwent continuous positive airway pressure therapy (CPAP). Effects of CPAP therapy on MPN-symptom assessment form total symptom scores (MPN-SAF TSS), JAK2V617F, MPL and CALR allelic burden, and exploratory endpoints of changes in inflammatory and thrombotic markers were ascertained (Figure 1). Comparisons with observational cohorts were planned to ascertain changes in the above endpoints at 0-, 3- and 6-months intervals (Figure 1). Based on a 40% reduction in allele burden (SD of 25%) and correlation of 0.5 between paired measurements, it was estimated that using a paired t-test with 27 evaluable patients will provide a 95% power to detect a 20% change in JAK2V617F burden from 40% to 20%. Similarly, assuming a 50% correlation (SD of 16) between pre- and post-therapy MPN-SAF TSS scores, 27 evaluable patients will provide a 80% power to detect a change of 10 at the two-sided 0.025 significance level. Results: Screening for OSA in patients with ET and PV revealed a high prevalence of OSA risk based on STOP-BANG scores. 26/29 males (mean age 63.6±11.8 years; BMI 29±3.3) and 16/26 females (mean age 61.5±12.8 years; BMI 28.2±6.5) had STOP-BANG scores of 3 or more. 8 patients with PV and ET have so far been enrolled into this study. 6/8 patients (age ranges from 41-74 years; 4 females and 2 males) with OSA (AHI 5-56 events/hr; 4% oxygen desaturation index 4.7-30/hr) underwent CPAP therapy. 1/6 patients in the CPAP arm did not tolerate CPAP and was excluded. 5/6 patients completed study procedures as did 2 additional patients without OSA in the observational study arm. Of 5/6 patients undertaking CPAP, 3/5 had the JAK2V617F mutations whereas 2/5 had the CALR mutation. JAK2V617F allele burdens at baseline in 2/5 patients were 80.7% and 4% at baseline and reduced to 73% and 1% at 6 months respectively whereas the third patient had undetectable JAK2V617F burdens throughout the study. All except one patient experienced improvement in MPN-SAF TSS scores after 6 months of CPAP therapy. While all 5 patients treated with CPAP showed improvements in C-reactive protein levels, analysis of NFkB1, TNF and IL-6 transcript levels showed mixed results. Similar mixed results were found with hypoxia-inducible factor (HIF) target gene expression ( SLC2A1, VEGF-A, EDN1) and markers of iron turnover (% transferrin saturation, transferrin, iron and ferritin levels) despite reduction in erythropoietin values in 4/5 patients with CPAP therapy at 6 months. Conclusions: Given the significant likelihood of OSA in patients with PV and ET (as based on STOP-BANG scores of 3 or more), there is need to evaluate and treat for OSA. Preliminary results show abnormalities in inflammatory markers with reductions in C-reactive protein and erythropoietin levels following CPAP therapy even though mixed results were noted in inflammatory and HIF-target gene transcripts, and markers of iron turnover. Larger studies and longer follow-up are required to understand the impact of OSA on not only the thrombotic and inflammatory milieu in patients with MPNs, but also the benefit of treating on prevention of disease progression and thrombotic manifestations common in MPNs. Funding: Huntsman Interventional Trial Grant CTO #HCI-17-HEM 28.

Combined Myeloid and Lymphoid Malignancies in 13 Elderly Patients

Disclosures Myeloid malignancies such as myelodysplasia (MDS) often evolve from age related clonal hematopoiesis (CH) with progression of variant allele frequencies. The Philadelphia negative myeloproliferative neoplasms (MPN) polythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF) are associated with mutations in JAK2, CALR, or MPL. Multiple myeloma (MM) and monoclonal gammopathies (MGUS) are felt to be age related, and the malignant cell is of lymphoid origin. Burkitt's Lymphoma is associated with EBV exposure and dysregulation of c-myc. However the etiology of most lymphoproliferative disorders (LPD) is not defined, but immune dysregulation may be causative. The combination of myeloid and lymphoid malignancies are not recognized to be a common occurrence; however within a three year period 13 patients with combined myeloid and lymphoid malignancies were detected in a single community practice. DATA Five patients had combined myeloid and lymphoid malignancies diagnosed concurrently. Three had a lymphoid disorder and then developed a myeloid disorder. Five had a myeloid disorder followed by a lymphoid disorder. Three patients had multiple myeloma (MM) and two had MGUS. Initially all patients responded to standard therapies, One patient at 87 years died from end stage renal disease likely related to her myeloma. Another patient with CLL and PV died at 92 years from an epithelial malignancy. Concurrent diagnoses Age at diagnosis (years) CLL ET 76MGUS MDS 77MM MDS 78MM MDS (RSBA) 85 5) DLBCL MF. 60 LPD/MM followed by a Age at initial diagnosis (years) and time to second diagnosis myeloid disorder. 1) MZL MF 58 15 months 2) MM ET 83 7 months 3) CLL PV 86 4 years Myeloid disorder followed by a LPD/MGUS MDS DLBCL 76 3 monthsMDS MGUS 78 30 monthsTP CLL 15 60 yearsET MyF 77 65 monthsET CLL 60 15 years (CLL chronic lymphocytic leukemia, DLBCL diffuse large B cell lymphoma, MF myelofibrosis, MyF mycosis fungoides, MZL mantle zone lymphoma, RSBA ringed sideroblastic anemia, TP inherited thrombocytopenia) JAK2 mutations were found in three of the four ET patients and in the one PV patient. One MF patient and one ET patient were negative for the JAK2 and CALR mutations. The mutation status of the other MF patient was not known. At diagnosis the patient with inherited thrombocytopenia was suspected to have a myeloid disorder. Combined myeloid and lymphoid malignancies is not well defined and is a seemingly uncommon event. Yet an Italian study demonstrated that MPN patients with JAK2 mutations have a 2.8-3.4 fold increased risk of developing a LPD compared with an age matched population (1). The linkage is unclear. Immune senescence may be important for the development of LPD observed in the elderly. Also long term latency of many years between the JAK2V617F mutation acquisition and MPN presentation has been documented (2). The occurrence of both myeloid disorders and LPD is not well recognized. Future studies may provide insights into the mechanisms underlying these disorders. Increasing genetic complexity and immune senescence associated with aging likely plays a major role. The limitations of this study are its small size, single community investigator, retrospective clinical nature, and the lack of gene sequencing and other molecular studies in most if not all of the patients. This observation was noted over three years in a single community practice which strongly implies that combined occurrence may be more common than recognized and suggests that further investigation is warranted. Boxer none, Denes none

The Epidemiology of Cardiovascular Disease in African American Patients with Myeloid Neoplasms: A SEER Data Analysis

Introduction: Cardiovascular disease (CVD) mortality rates are higher in cancer survivors compared to the general population. Numerous studies have reported racial disparities in CVD mortality among cancer survivors. However, there is a lack of research exploring CVD mortality specifically in African American (AA) patients (pts) with myelodysplastic syndromes (MDS) and myeloproliferative neoplasms (MPN). To address this gap, we conducted a comprehensive population-based study to analyze cardiovascular mortality in the AA population with MDS and MPN. Methods and Statistical analysis: In Surveillance, Epidemiology, and End Results (SEER) database using the 17 registries, we identified cases of essential thrombocythemia (ET), Polycythemia Vera (PV), Primary Myelofibrosis (PMF), and Myelodysplastic syndromes (MDS) in AA population diagnosed between 2001-2020, with the diagnosis age >=20. CVD deaths included deaths from heart diseases, hypertension without heart disease, cerebrovascular diseases, atherosclerosis, and diabetes mellitus, based on the SEER Causes of Death Register and International Classification of Diseases (10th Revision, ICD10). Death rates were calculated by dividing the number of deaths over person-years of follow-up. We also estimated the standardized mortality ratios (SMR by dividing the observed cardiovascular deaths rates in our sample over expected CVD death rates of general population with no cancer, matched to age, gender and ethnicity. All analyses were performed by SEER*Stat 8.4.1.2 and R 4.2.2. Results: The study included 8135 patients, with following diagnoses: ET (n= 2317), PV (n= 1231), PMF (n= 377) and MDS (n= 4210). Overall, 2640 of the total study population (32.45%) died, of which 39.5% were CVD deaths. The mean follow up for PV, ET, PMF and MDS cohorts was 6.44, 5.95, 3.67 and 3.82 years, respectively (Table 1). The CVD mortality rate per 1,000 person-years in PV, ET and PMF subgroups were 17.9, 14.95, and 29.6, respectively. Notably, the rate was highest in the MDS subgroup, 40.37 compared to other subgroups (P<0.01). Comparing the CVD mortality of each risk group to the general US AA population, we observed significantly increased CVD SMRs. These were highest in PMF and MDS (SMR, 3.07; 95% CI, 2.2-4.16 and 2.25; 95% CI, 2.08-2.43, respectively), followed by PV (SMR, 1.75; 95% CI, 1.47-2.06) and ET (SMR, 1.67; 95% CI, 1.45-1.92).When comparing CVD mortality to the general CVD mortality rate in the AA population, we found higher rates across all age groups, including SMR, 13.16; 95% CI, 4.27- 30.72 in 20-29 yrs, SMR, 5.4; 95% CI, 2.95- 9.06 in 30-39 yrs, (SMR, 2.20; 95% CI, 1.92- 2.52) in 60-69 yrs, (SMR, 1.87; 95% CI, 1.67- 2.1) in 70-79 yrs (Figure 1). Conclusion: Our analysis highlights the magnitude of CVD-related deaths in the AA population with MDS and MPN. Among studied subgroups, the impact was highest in patients with MDS. This could be explained by a shared mechanism of CVD pathogenesis with MDS and clonal hematopoiesis of indeterminate potential (CHIP). In addition, we report a higher risk of CVD mortality at younger ages in AA pts relative to older age group. Because CVD-related mortality is high in AA with MDS and MPN, introduction of preventative cardiology services after diagnosis might be warranted to improve survival.

Quantification of JAK2 V167F in Patients with Myeloproliferative Neoplasms: Comparison of NGS and Digital PCR with Quantitative PCR

Introduction: JAK2 V617F is the most common mutation in the Philadelphia-negative myeloproliferative neoplasms (MPN), detected in 97% of polycythemia vera (PV), and approximately 55% of essential thrombocythemia (ET) and primary myelofibrosis (PMF) cases. According to the WHO, JAK2 V617F positivity is a major criteria for PV, ET or PMF diagnosis. But JAK2 V617F quantification at diagnosis could be useful since a high allelic frequency (or VAF) has been associated with increased symptom burden in PV, risk of thrombotic events in ET and progression in PMF. The current gold standard technique for JAK2 V617F quantification is allele-specific quantitative PCR (qPCR). However, digital PCR (dPCR) is increasingly being employed since it permits absolute quantification of JAK2 V617F without the need for a standard curve. QPCR vs. dPCR comparisons have shown high conformance between the two methods. Moreover, next-generation sequencing technologies (NGS) are increasingly used for MPN diagnosis. The aim of this study was to evaluate the concordance between dPCR and NGS for JAK2 V617F quantification at diagnosis. Methods: JAK2 V617F was quantified in the same sample of genomic DNA, extracted from total leukocytes from peripheral blood or bone marrow at diagnosis, by digital PCR (dPCR) and by NGS. The Absolute Q™ Liquid Biopsy dPCR Assay (JAK2 12600) was used in the QuantStudio™ Absolute Q™ Digital PCR System (Applied Biosystems) with 25 ng DNA. This assay quantifies the number of JAK2 WT-VIC and JAK2 V617F-FAM positive signals in 20000 partitions, determined as copies JAK2 V617F/µl input sample, and expressed as percentage VAF, with a limit of detection of 0.1%. NGS was performed with the MiSeq (Illumina) platform and the targeted 30-gene panel Myeloid Solution™ (SOPHiA GENETICS) using 200 ng DNA. VAF was determined as the number of variant reads divided by the number of total reads (reported as a percentage), with a limit of detection of 2.5%. Statistical analyses were performed using R-commander version 2.8. P-values <0.05 were considered statistically significant. Results: The quantification of JAK2 V617F was carried out in a total of 52 patient samples with both techniques. Of the 52 patients, 5 had a diagnosis of ET and 47 had PV. The average VAF of JAK2 V617F using dPCR was 14.1% and 48.2%, and 17.1% and 47.6% using NGS for ET patients and PV patients, respectively. The concordance of positivity for JAK2 V617F between the two methods was 100%. With dPCR, the average VAF of JAK2 V617F was 44.62% (range 2.7%-100%). With NGS, the average VAF of JAK2 V617F was 44.95% (range 2.5%-96.5%), with an average coverage/read depth >3500 reads. At diagnosis, there was no difference in the mean VAF of JAK2 V617F determined using dPCR vs. NGS (44.62 vs. 44.95, p=0.792, paired Student t-test). There was an excellent correlation between the VAF of JAK2 V617F determined using dPCR vs. NGS (Pearson correlation coefficient 0.944, p<0.001; Figure 1). Only 7 samples had a deviation >10% in the VAF quantification. These determinations are indicated in orange in the graph and listed in the table . The cause of 2/7 deviations might have been a limited DNA volume/concentration available for dPCR. The high concordance of variant quantification by dPCR andNGS was maintained for JAK2 V617F with low VAFs (≤20%, mean 12.0% vs. 11.8%, respectively; p=0.840) and high VAFs (≥80%, mean 90.6% vs. 89.9%, respectively; p=0.858). Conclusions: Overall, excellent correlation was observed between the VAF of JAK2 V617F obtained using dPCR and NGS, showing that NGS is a robust quantification method. However, 7 samples had a difference >10% VAF, with a deviation >25% in 3 cases. Standardization of molecular techniques for JAK2 V617F quantification is important if the VAF is to be monitored during MPN patient follow-up as a biomarker for disease evolution and for response to treatment, with VAF reductions shown for pegylated interferon and ruxolitinib. DPCR might be better suited for follow-up quantification due to its higher sensitivity and lower price, while NGS at diagnosis, apart from detecting and quantifying JAK2 V617F at baseline, has the advantage of providing information on other gene mutations with prognostic value.

Glycated Hemoglobin (HbA1c) and Thrombotic Risk in Polycythemia Vera and Essential Thrombocythemia

BACKGROUND: Essential thrombocythemia (ET) and polycythemia vera (PV) are BCR::ABL1 negative myeloproliferative neoplasms (MPNs) characterized by overproduction of one or more mature myeloid cell lineages and high thrombotic risk. Diabetes mellitus (DM) is a rare cardiovascular (CV) comorbidity in MPNs and the optimal treatment target levels of glycated hemoglobin (HbA1c) in MPNs remain unknown. OBJECTIVE&METHODS: This multicenter study was conducted in Croatia and Serbia in the period between 01/1997 and 01/23 and investigated clinical correlations of HbA1c in ET and PV patients whose diagnoses were reassessed according to 2016 WHO criteria. We retrospectively collected data regarding diabetic ET and PV patients with available HbA1c at disease diagnosis, stratified them according to HbA1c levels, and compared their clinical outcomes to a control group of 93 non-diabetic ET and PV patients. Outcomes of interest were time to thrombosis (TTT; death as a censoring event) and overall survival (OS). Survival analyses were based on Kaplan-Meier method and performed with log-rank test and the Cox-regression analysis. The study was approved by Ethics Committees from all participating centers. RESULTS: We included 109 MPN patients (33 ET and 76 PV) with DM (all type II); median age was 69 years (range 37-86), 60 (55%) were females, 81 (74.3%) were JAK2- and 10 (9.2%) CALR-positive. Ninety-two (84.4%) patients were classified as high-risk (age>60 years or prior thrombosis), 68 (62.4%) received hydroxyurea (HU), 91 (83.5%) had arterial hypertension, 44 (40.4%) hyperlipidemia, and 36 (33%) were smokers. The median follow-up time was 38 months; 16 (14.7%) thrombotic (13 arterial and 3 venous) events and 25 deaths (22.9%) occured during this time. Median HbA1c in diabetic MPN patients was 6.8% (range 4.8-16.2%). There were no associations of HbA1c with disease phenotype, age, sex, mutational status, prior thrombosis, presence of individual CV risk factors, or any of the blood cell count components (p>0.050 for all analyses). ROC curve defined the optimal HbA1c cut-off level of ≥7.2% for the best discrimination of thrombotic events in MPN patients with DM. Diabetic MPN patients with low HbA1c (<7.2%) had similar TTT (median 182 months) as non-diabetic MPN patients (median 197 months) whereas those with higher HbA1c (≥7.2%) had significantly worse TTT (median 124 months; HR 3.76, p=0.012), as presented in Figure 1A. The detrimental effect of high HbA1c was evident in high-risk (HR 3.2, p=0.031) but not in low-risk diabetic MPN patients (p=0.115). Also, JAK2-negative diabetic MPN patients with higher HbA1c had inferior TTT when compared to their counterparts (HR 28.17, p<0.001), with no difference among JAK2-positive patients (Figure 1B). There were significant interactions between high HbA1c, thrombotic risk, and advanced age (p=0.026), higher leukocytes (p=0.028), higher erythrocytes (p=0.007), higher platelets (p=0.034), higher hematocrit (p=0.007) and higher hemoglobin (p=0.013), with older age and higher blood counts favoring higher thrombotic risk associated with high HbA1c. There was no difference in OS when comparing non-diabetic to diabetic MPN patients with respect to HbA1c (p=0.209). In the multivariate Cox regression model, high HbA1c (HR 5.04, p=0.013) remained as the only variable associated with inferior TTT among diabetic MPN patients when additionally controlling for age, sex, history of thrombosis, presence of JAK2 mutation, HU treatment, baseline leukocyte counts, and the presence of at least one other CV risk factor. DISCUSSION: This study demonstrated that diabetic MPN patients with low (<7.2%) HbA1c had similar TTT as non-diabetic patients suggesting that stringent control of DM in MPNs is extremely important; this effect was most evident in JAK2-negative diabetic MPN patients. Also, significant interactions with high trombotic risk were found between high HbA1c, older age, and different myeloid cell lineages, suggesting that uncontrolled DM acts synergistically with MPN clone and underlies CV development. However, no correlations between HbA1c and blood cell counts were detected, indicating that HbA1c measurements may not be accurrate in MPNs for DM diagnosis. The lack of association of high HbA1c with OS is probably related to optimal post-thrombotic management. Future studies are needed to elucidate optimal HbA1c values for the diagnosis and treatment of DM in MPNs.

Classification of Philadelphia-Negative MPN As Low Risk and High Risk MPN Based on Peripheral Blood Values and Molecular Genetics Only

Background: Philadelphia-negative myeloproliferative neoplasms (Ph -MPN) are characterized by overproduction of differentiated hematopoietic cells mediated in the majority of cases by mutations in JAK2, MPL or CALR (MPN driver genes). Ph - MPN include polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF) and MPN, unclassifiable (MPN-U) which differ in clinical presentation, prognosis, fibrosis and leukemic transformation rate as well as therapeutic options. However, WHO based classification requires experienced pathologists, in particular to diagnose prefibrotic PMF as high risk MPN, and thus remains observer dependent. Aim: Observer independent classification of Ph - MPN solely based on molecular genetics and peripheral blood (PB) parameters. Patients and Methods: We analyzed 267 Ph - MPN cases diagnosed as ET (n=76), PV (n=74), PMF (n=68) or MPN-U (n=49) following the WHO4R classification including only patients with an MPN driver mutation (median age: 68 years [22-91]; female: 41%; median follow-up: 5 years). All samples were analyzed by cytomorphology and whole genome sequencing (median coverage 100x). Mutation status of 20 genes associated with myeloid malignancies were analyzed in detail. Results: Genomic landscape of the MPN cohort showed mutations in JAK2 in 222 (83%) (n=132: single mutation; n=90: either mutation and copy neutral loss of heterozygosity or mutation and 9p gain), in CALR in 36 (14%), and in MPL in 9 (3%) patients. The median number of mutations per patient was two (range: 1-6). Within the cohort, 141 patients (53%) harbored MPN driver mutations only, while in 126 (47%) one to 5 additional mutations were found. The most frequent additional mutations were ASXL1 (n=50), TET2 (n=49; thereof 15 biallelic), SRSF2 (n=26), DNMT3A (n=18), U2AF1 (n=11) and TP53 (n=9; thereof 3 biallelic). Regarding PB parameters, high WBC (≥11×10 9/ L) were detected in 127 patients (48%), high PLT (≥450×10 9/ L) in 116 (43%) and anemia (HB <♂12 or ♀11 g/dL) in 50 patients (19%). We then performed Cox regression analyses for overall survival (OS) including only genetic abnormalities and PB values. In univariate analyses, biallelic TET2 inactivation ( TET2bi: hazard ratio/HR: 3.789), RUNX1 (n=4; HR: 13.479), ASXL1 (HR: 1.886), SRSF2 (HR: 3.218) mutations as well as high PLT (HR: 0.440), high WBC (HR: 1.998) and PB blasts >1% (n=57; HR: 1.904) showed significant associations with OS (for all p<0.02), while no effect was observed for MPN driver mutations, DNMT3A and monoallelic TET2 mutations. In addition, anemia showed a trend towards poor prognosis (HR: 1.595; p=0.079). Following this, we determined high and low risk MPN. In the absence of thrombocytosis, high risk MPN was defined if any of the four following risk factors were present: i) mutation in ASXL1 or SRSF2 or RUNX1 or TET2bi, ii) PB blasts >1%, iii) high WBC or iv) anemia. In the presence of thrombocytosis, at least two of these risk factors were required (Figure 1). Survival analysis revealed a significantly worse median OS of high risk (n=137; 51%) compared to low risk MPN (n=130; 49%) (8 years vs. not reached; p<0.001). This proposed novel stratification reflected prognosis better than WHO entities (median OS: MPN-U: 7 years; MF: 8 years; PV/ ET not reached; overall p=0.001) (Figure 1A). All 76 ET cases (100%) and 44/74 PV cases (59%) were classified as low risk MPN, while 63/68 PMF cases (93%) and 44/49 MPN-U cases (90%) were classified as high risk MPN (Figure 1B). Within low risk and high risk MPN, no significant OS differences were observed between the WHO entities ( p=0.114 and p=0.355, respectively). Conclusions: JAK2-pathway mutated Ph - MPN can be categorized into low and high risk MPN based on molecular genetics and PB values only. The presence of these objectively assessable risk factors in a patient with ET or PV warrants for a profound reevaluation of bone marrow histology (eventually by a reference pathologist for MPN) and clinical course before a high risk MPN (including prefibrotic PMF) can be ruled out. Whether the predictive value of low risk MPN based on molecular genetics and PB values only could be sufficient to omit BM biopsy in selected patients, needs to be evaluated in further prospective studies.

Enhanced Cardiovascular Risk Assessment Incorporating Natural Language Processing and Qrisk-3 Score Determination in Patients with Essential Thrombocythaemia

Introduction: Fundamental to management of patients with essential thrombocythaemia (ET) is assessment, and reduction of thrombotic risk. We present a machine learning approach to summarise patient electronic health records (EHR) to determine prevalence of cardiovascular comorbidities and risk factors. We then review use of the QRISK-3 score to assess cardiovascular risk. Methods: We used a natural language processing (NLP) pipeline to identify mentions of hypertension (HTN), hypercholesterolaemia (HC), diabetes mellitus (DM), smoking (SM), unspecified thrombosis (VTE), deep vein thrombosis (DVT), pulmonary embolism (PE), portal vein thrombosis (PVT), myocardial infarction (MI) and stroke (CVA) in EHR. CogStack is an information retrieval and extraction architecture incorporating structured and unstructured EHR components. Data extracted from CogStack was processed by a medical concept annotation toolkit (MedCAT). MedCAT was used to disambiguate and capture synonyms and acronyms for Systematized Nomenclature of Medicine-Clinical Terms (SNOMED-CT) concepts. Using deep learning MedCAT determined linguistic and grammatical context such as negation, subject, and temporality. The base MedCAT model was trained in an unsupervised manner on >18 million EHR documents and this was further fine-tuned through 500 clinician annotated haematology documents. MedCAT mapped mentions of relevant concepts to respective SNOMED-CT codes and total counts were aggregated and grouped by individual patient. Manual validations were performed and an optimizer was applied to convert counts to a binary state by applying a threshold, above which a patient's condition was inferred to be present (Fig. i). QRISK-3 is an advanced validated score incorporating age, ethnicity, body mass index and other cardiovascular risk factors to determine 10-year cardiovascular risk in people aged 25-84. Results: 12905 documents from 560 ET patients were reviewed (median 20 per patient, IQR 8-34). In the manual validation dataset (n=120), MedCAT achieved excellent real-world F1 scores (model accuracy) for most concepts (HTN 0.91, HC 0.81, DM 1.0, VTE 0.73, CVA 0.87 and MI 0.67). Using a threshold of >2 mentions to define a positive population; HTN was identified in 21.3% (119) of patients, DM in 4.6% (26), MI in 3.6% (20), CVA in 7.7% (43), VTE in 8% (45), DVT in 1.4% (8), PE in 1.8% (10), PVT in 1.3% (7) and positive smoking status in 6.6% (37). HC was identified in 9.6% (54) using a threshold >1. 52% (28) of patients with HC and 69.2% (18) of those with DM also had HTN. Obesity was not identified in any patients using this approach. Patients with a diagnosis of HTN were more likely to have CVA than those without (15:104 vs 28:413, p=0.03). Patients with HTN were also more likely to have VTE (13:106 vs 19:422, p=0.01). Of patients with CVA/MI; 58.1% (25) /55% (11) had this event pre or at diagnosis and 30.2% (13)/ 10% (2) while receiving cytoreductive therapy. QRISK-3 analysis was performed in 32 patients with prior thrombosis and baseline criteria to evaluate predictive value; then 137 patients classified as low or intermediate (LIM) risk and not receiving cytoreductive therapy. Mean QRISK-3 was 8 in the thrombosis group, validating its relevance, and 2.5 (p<0.0001, Fig. ii) in the LIM cohort. Using the recognised QRISK-3 score threshold of >7.5 to define a high-risk population, 5.1% (7) patients from the LIM group were reclassified as high-risk due to additional comorbidities relevant to QRISK-3 including HTN in 8% (11), migraine 7.3% (10), DM 2.2% (3), severe mental illness 2.9% (4) and antipsychotic medication 0.7% (1). Discussion: We describe a novel approach to cardiovascular risk assessment in patients with ET, incorporating machine learning, allowing large volume data analysis, and detailed risk assessment using QRISK-3 scoring. We provide a rare ‘real-world’ report on the prevalence of comorbidities in this group, confirming increased CVA and VTE in patients with HTN. A previous report of 891 patients with ET showed prevalence of 5% for CVA, 2% for MI and 4% for VTE, suggesting that detection rate using our approach is within acceptable limits (Carobbio et al., Blood, 2011). Finally, as a novel finding, we show that QRISK-3 scoring is predictive of increased thrombotic risk and identifies a small group of patients who should be considered high-risk and may benefit from cytoreductive therapy, that are not detected using standard approaches.

An Atypical Somatic Calr Variant Acquired in Cis to a Germline Calr variant Induces Constitutive Signaling of the Thrombopoietin Receptor and Results in Essential Thrombocythemia

Acquired mutations in the gene encoding the endoplasmic reticulum (ER) chaperone calreticulin (CALR) are responsible for ~ 30% of essential thrombocythemia (ET) and myelofibrosis (MF) cases. Two CALR mutations, a deletion of 52 base pairs (del52) and an insertion of 5 base pairs (ins5) are the most frequent in ET and MF patients. All CALR mutations result in a +1-frameshift leading to 1) the replacement of the negatively-charged wild-type (WT) C-terminus that binds calcium in the ER by a positively-charged mutant tail including 44 residues that are common to all CALR mutant proteins and 2) the loss of the ER retention KDEL; together leading to the deregulation of calcium homeostasis. The CALR mutants are also secreted and bind to MPL in the ER but induce its constitutive dimerization and downstream signaling pathways at the cell surface. A 16-year-old girl presented with a platelet count of 797 x 10 3/mL rising to 1,228 x 10 3/mL within 2 years. After Informed Consent, we detected two atypical CALR variants in her blood cells by NGS analysis: V1 (c.1122-1125del) at 47% variant allele frequency (VAF) and V2 (c.1227-1231del) in cis of the V1 leading to V1-V2 (c.1122-1125del ; c.1227-1231del) at 5% VAF. The presence of V1 in blood and nails from the propositus and her healthy mother confirmed its germline origin. The V1-V2 was only found in the propositus at 5% in isolated monocytes and at very low levels in NK and B cells, confirming its somatic acquisition. The germline V1 induces a frameshift resulting in the replacement of the CALR WT C-terminus by the positively charged 44 residue-long C-terminal mutant tail present in del52 and ins5 and the loss of KDEL together with an insertion of 10 amino acids not present in CALR del52 nor ins5. In contrast, the V1-V2 generates a similar but shortened C-terminus containing the Arg-rich MPL binding site and KDEL (Fig. 1A). To investigate the functional impact of these CALR variants, we cloned V1 and V1-V2 with a N-terminal hemagglutinin (HA) tag as well as CALR WT and del52 as controls in a retroviral plasmid. Viral particles were produced to transduce Ba/F3 cell lines expressing MPL. Structural modeling using AlphaFold was used to investigate the role of KDEL restoration in V1-V2 in producing an oncogenic protein leading to ET. Both CALR WT and V1-V2 variants that contain the KDEL motif were detected to a similar extent in Ba/F3-MPL cell lysates. In contrast, del52 and V1, that lost the ER-retention KDEL motif, were barely detected in cell lysates. Unexpectedly, despite the presence of the KDEL motif, V1-V2 was found at a similar level than del52 at the Ba/F3-MPL cell surface. In contrast, V1 was barely detectable at the cell surface, like CALR WT. In order to investigate the role of the KDEL in V1-V2 cell surface expression, we generated a CALR WT lacking the KDEL and added the KDEL motif to del52. The presence of the KDEL motif stabilized the intracellular expression of del52 without affecting cell surface localization while the removal of the KDEL motif in CALR WT appeared to destabilize the protein and induce a slight leak to the cell surface. Structural modeling using AlphaFold predicted that the KDEL in V1-V2 structure is accessible to KDEL receptors, suggesting that the motif may be masked by the interaction of V1-V2 with MPL while trafficking to the cell surface. Indeed, cell-surface expression of V1-V2 was decreased in Ba/F3 that do not express MPL. We show that V1-V2, but not V1, constitutively activates the phosphorylation of STATs, ERK and AKT in Ba/F3-MPL. TPO further increases activation of STATs but not of AKT and ERK by V1-V2 and del52. Coherently, V1-V2, but not V1, sustained oncogenic MPL stimulation able to sustain cell autonomous Ba/F3-MPL cell proliferation (Fig. 1B). Both del52 and V1-V2 up-regulated BCL-2 mRNA. Dose-response cytotoxicity assays with the BCL-2 inhibitor venetoclax showed that these two mutants are sensitive to lower doses compared to CALR WT- or V1-expressing Ba/F3-MPL cells. This is the first report of a germline loss-of-function CALR variant (V1) expressed as an unstable protein and that might predispose to the acquisition of a somatic gain-of-function CALR variant (V1-V2) responsible for ET. The presence of KDEL in V1-V2 leads to stabilized CALR expression that does not prevent cell surface localization. Moreover, it leads to induction of MPL signaling and cytokine-independent cell growth.

Myeloproliferative Neoplasms Are Associated with Increased Risk of Major Adverse Limb Events Among Patients Hospitalized for Peripheral Arterial Disease

Background: Myeloproliferative neoplasms (MPN), including essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF), are at high risk of cardiovascular (CV) disease, including atherosclerosis and peripheral arterial disease (PAD). Major adverse limb events (MALE), including major amputation, are dreaded complications of PAD that portend poor prognosis. Among patients with MPN, arterial thrombotic events are common and prior studies suggest that PAD is a risk factor for arterial thrombosis in this patient population. However, there are limited data on outcomes of patients with MPN and PAD. Therefore, the effect of MPN status on MALE, in-hospital death and unplanned readmissions among patients hospitalized for PAD. Methods: This was a retrospective cohort analysis of the National Readmission Database (NRD) of adult patients with a primary diagnosis of PAD from 2017 and 2018 with or without a history of MPN, as identified by ICD-10 codes. Primary outcome was MALE which was a composite of index hospitalization death, major amputation, 30-day readmission for PAD, lower extremity ulceration, gangrene, rest pain, major amputation or arterial thromboembolism. Secondary outcomes were bleeding complications at index hospitalization (including gastrointestinal, intracranial, post-procedure, and retroperitoneal bleeding), 90-day readmissions for any-cause, PAD, CV reason (including PAD, myocardial infarction, stroke, or heart failure), and bleeding. Propensity scores (PS) for estimating probability of MPN were calculated using non-parsimonious multivariable logistic regression that included all baseline patient characteristics examined. PS matching (PSM) 1 MPN case to 5 non-MPN controls was performed. Patients between groups were compared and standardized mean difference (SMD) was calculated for variables before and after PSM. Imbalances between groups were insignificant if SMD for a given co-variable was < 0.10. Odds ratio (OR) for MALE and in-hospital outcomes were calculated using logistic regression. For 90-day readmission analyses, patients who died during index hospitalization were excluded and hazard ratios (HR) were estimated using Cox proportional hazards regression. Risk factors for MALE among patients with MPN were assessed using backward stepwise logistic regression. Results: After PSM, 1702 patients with MPN (1338 ET, 273 PV, 91 PMF) were matched with 8510 non-MPN patients. After PSM, variables were well-balanced between patients with and without MPN, Table. MPN was associated with increased risk of MALE (40.3% vs 27.9%, OR 1.75, 95% CI 1.57 - 1.95) and major amputation at index hospitalization (34.6% vs 23.5%, OR 1.72, 95% CI 1.54 - 1.92) but not in-hospital death (1.8% vs 2.0%, OR 0.92, 95% CI 0.63 - 1.36) or bleeding (17.5% vs 19.5%, OR 0.90, 95% CI 0.79 - 1.03). MPN was associated with increased risk of 90-day readmission for any-cause (HR 1.21, 95% CI 1.10 - 1.33), PAD (HR 1.22, 95% CI 1.11 - 1.35), and CV reason (HR 1.32, 95% CI 1.17 - 1.49) but not for bleeding (HR 1.33, 95% CI 0.90 - 1.97), Figure. Among patients with MPN, ET (OR 2.08, 95% CI 1.44 - 3.01), end-stage renal disease (OR 1.59, 95% CI 1.12 - 3.11), anemia (OR 1.75, 95% CI 1.39 - 2.21), gangrene (HR 1.95, 95% CI 1.38 - 2.75), and sepsis (OR 1.90, 95% CI 1.36 - 2.66) were associated with increased risk of MALE while compared surgical bypass (OR 0.46, 95% CI 0.31 - 0.68) and endovascular revascularization (OR 0.71, 95% CI 0.54 - 0.94) during index hospitalization were associated with decreased risk of MALE. Conclusions: Among patients hospitalized for PAD, MPN was associated with increased risk of MALE and 90-day readmission for any-cause, PAD, and CV reasons. Among patients with MPN, ET was associated with increased risk of MALE while revascularization during index hospitalization was associated with decreased risk. Further studies are needed to further elucidate risk of MALE and adverse CV events among patients with MPN in order to improve clinical outcomes in this high-risk patient population.