Szuber, Natasha

Background A JAK2 mutation is detected in almost all patients with polycythemia vera (PV) and in ⁓50% of those with essential thrombocythemia (ET). The two diseases also share characteristic clinical and bone marrow morphological traits, suggesting they exist on a disease continuum rather than representing discrete entities. The objective of the current study was to compare clinical and genetic characteristics as well as long-term outcome between formally-defined PV vs. JAK2-mutated ET vs. JAK2-wild-type (WT) ET. Methods Study patients were retrospectively recruited from Mayo Clinic, USA databases (1967-2024). Diagnostic criteria were according to the International Consensus Classification (ICC; Blood 2022;140:1200). All study patients were fully annotated for JAK2, CALR, and MPL mutations while cytogenetic and additional next-generation sequencing (NGS)-derived mutation information was available in a subset of patients. Conventional statistical methods were employed for phenotypic comparisons and survival analysis. Results Among 2,010 study patients, 1,010 had PV, 617 (63%) JAK2-mutated ET, and 383 JAK2-WT ET (CALR 26%; MPL 3%; triple-negative 9%). Phenotypic comparisons revealed older age distribution in PV compared to JAK2-mutated ET (p=0.03) and the latter compared to JAK2-WT ET (p<0.01). Females were represented more in JAK2-mutated ET (69%), compared to both PV (49%; p<0.01) and JAK2-WT ET (54%; p<0.01). The frequencies of leukocytosis, palpable splenomegaly, constitutional symptoms, diabetes, hypertension, and abnormal karyotype were all significantly higher in PV, compared to both groups of ET, while JAK2-mutated compared to JAK2-WT ET displayed higher leukocyte count and incidence of hypertension. The incidences of arterial thrombosis at/prior to diagnosis were 14%, 16%, and 10% in PV, JAK2-mutated and WT ET, respectively (P=0.03), and venous thrombosis 14%, 13%, and 6% (p<0.01). After a median follow-up of 8.6 years, 632 (32%) deaths, 329 (16%) fibrotic progressions, 79 (4%) leukemic transformations, and 236 (12%) arterial and 202 (10%) venous thrombotic events were recorded, among all 2,010 study patients. Median overall survival was 19.3 years for PV vs. 17.8 years for JAK2-mutated ET vs. 23 years for JAK2-WT ET (p<0.01); however, the significant difference in favor of JAK2-WT ET was no longer apparent when analysis was adjusted for age and sex (p=0.15) and subsequently for other risk factors (p=0.86). All-inclusive multivariable analysis identified older age (p<0.01), male sex (p<0.01), higher leukocyte count (p<0.01), and arterial thrombosis history (p<0.01), but not the distinction between PV, JAK2-mutated, and JAK2-WT ET (p=0.9), to be independently associated with shortened survival. Leukemia-free survival was similar between PV and either JAK2-mutated (p=0.5) or JAK2-WT (p=0.1) ET. On the other hand, myelofibrosis-free survival was shorter in PV, compared to both JAK2-mutated (HR 1.8, 1.4-2.4; p<0.01) and JAK2-WT (HR 1.4. 1.0-1.8; p=0.03) ET. In multivariable analysis, older age (p<0.01), higher leukocyte count (p<0.01), PV vs. JAK2-mutated ET (HR 1.8; p<0.01), and JAK2-WT vs. JAK2-mutated ET (HR 1.6; p=0.01) were associated with a higher risk of fibrotic progression, with no difference noted between PV and JAK2-WT ET (p=0.4). Arterial thrombosis-free survival was similar between PV and JAK2-mutated ET (p=0.8). In univariate analysis, JAK2-WT ET vs. PV was associated with superior arterial thrombosis-free survival (p=0.02), but significance was lost when analysis was adjusted for arterial thrombosis history (p=0.1). Venous thrombosis-free survival favored JAK2-WT ET vs. PV (HR 0.3; p<0.01) and JAK2-mutated ET (HR 0.6; p=0.02) and the latter vs. PV (HR 0.6; p<0.01); the significant differences between PV and both groups of ET were sustained when analysis was adjusted for age, sex, and venous thrombosis history. Conclusions The current study highlights significant demographic and phenotypic differences between PV and JAK2-mutated ET. However, risk factor-adjusted overall, leukemia-free, and arterial thrombosis-free survival was not inferior in PV, compared to ET, regardless of the presence or absence of a JAK2 mutation in the latter. JAK2-WT ET was distinctly associated with a lower risk of venous thrombosis while JAK2-mutated ET appeared to be less vulnerable to fibrotic progression.

Abstract With emerging new drugs in myelofibrosis (MF), a robust and harmonized framework for defining the severity of anemia and response to treatment will enhance clinical investigation and facilitate interstudy comparisons. Accordingly, the lead authors on the 2013 edition of the International Working Group–European LeukemiaNet (IWG-ELN) response criteria in MF were summoned to revise their document with the intent to (1) account for gender-specific differences in determining hemoglobin levels for eligibility criteria; (2) revise the definition of transfusion-dependent anemia (TDA) based on current restrictive transfusion practices; and (3) provide a structurally simple and easy to apply response criteria that are sensitive enough to detect efficacy signals (minor response) and also account for major responses. The initial draft of the 2024 IWG-ELN proposed criteria was subsequently circulated around a wider group of international experts and their feedback incorporated. The proposed articles include new definitions for TDA (≥3 units in the 12 weeks before study enrollment) and hemoglobin thresholds for eligibility criteria (<10 g/dL for women and <11 g/dL for men). The revised document also provides separate (TDA vs non-TDA) and graded (major vs minor response) response criteria while preserving the requirement for a 12-week period of screening and observation on treatment.

AbstractChronic neutrophilic leukemia (CNL) is a rare BCR::ABL1‐negative myeloproliferative neoplasm (MPN) defined by persistent mature neutrophilic leukocytosis and bone marrow granulocyte hyperplasia. Atypical chronic myeloid leukemia (aCML) (myelodysplastic “[MDS]/MPN with neutrophilia” per World Health Organization [WHO]) is a MDS/MPN overlap disorder featuring dysplastic neutrophilia and circulating myeloid precursors. Both manifest with frequent hepatosplenomegaly and less commonly, bleeding, with high rates of leukemic transformation and death. The 2022 revised WHO classification conserved CNL diagnostic criteria of leukocytosis ≥25 × 109/L, neutrophils ≥80% with <10% circulating precursors, absence of dysplasia, and presence of an activating CSF3R mutation. ICC criteria are harmonized with those of other myeloid entities, with a key distinction being lower leukocytosis threshold (≥13 × 109/L) for cases CSF3R‐mutated. Criteria for aCML include leukocytosis ≥13 × 109/L, dysgranulopoiesis, circulating myeloid precursors ≥10%, and at least one cytopenia for MDS‐thresholds (ICC). In both classifications ASXL1 and SETBP1 (ICC), or SETBP1 ± ETNK1 (WHO) mutations can be used to support the diagnosis. Both diseases show hypercellular bone marrow due to a granulocytic proliferation, aCML distinguished by dysplasia in granulocytes ± other lineages. Absence of monocytosis, rare/no basophilia, or eosinophilia, <20% blasts, and exclusion of other MPN, MDS/MPN, and tyrosine kinase fusions, are mandated. Cytogenetic abnormalities are identified in ~1/3 of CNL and ~15–40% of aCML patients. The molecular signature of CNL is a driver mutation in colony‐stimulating factor 3 receptor—classically T618I, documented in >80% of cases. Atypical CML harbors a complex genomic backdrop with high rates of recurrent somatic mutations in ASXL1, SETBP1, TET2, SRSF2, EZH2, and less frequently in ETNK1. Leukemic transformation rates are ~10–25% and 30–40% for CNL and aCML, respectively. Overall survival is poor: 15–31 months in CNL and 12–20 months in aCML. The Mayo Clinic CNL risk model for survival stratifies patients according to platelets <160 × 109/L (2 points), leukocytes >60 × 109/L (1 point), and ASXL1 mutation (1 point); distinguishing low‐ (0–1 points) versus high‐risk (2–4 points) categories. The Mayo Clinic aCML risk model attributes 1 point each for: age >67 years, hemoglobin <10 g/dL, and TET2 mutation, delineating low‐ (0–1 risk factor) and high‐risk (≥2 risk factors) subgroups. Management is risk‐driven and symptom‐directed, with no current standard of care. Most commonly used agents include hydroxyurea, interferon, Janus kinase inhibitors, and hypomethylating agents, though none are disease‐modifying. Hematopoietic stem cell transplant is the only potentially curative modality and should be considered in eligible patients. Recent genetic profiling has disclosed CBL, CEBPA, EZH2, NRAS, TET2, and U2AF1 to represent high‐risk mutations in both entities. Actionable mutations (NRAS/KRAS, ETNK1) have also been identified, supporting novel agents targeting involved pathways. Preclinical and clinical studies evaluating new drugs (e.g., fedratinib, phase 2) and combinations are detailed.

Abstract Among 281 patients with essential thrombocythemia and calreticulin (CALR) mutation, we found a variant allele frequency of ≥60% to be associated with significantly shortened myelofibrosis-free survival, mostly apparent with CALR type-1 and CALR type-indeterminate mutations.

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), &gt;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 &gt;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 &gt;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 &gt;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 &gt;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 &gt;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&lt;.0001); AML and death not differ. Anemia (&lt;10g/dL) during the FU developed in 69% of CALR-high pts vs 18%, leukocytosis (&gt;15x10 9/L) in 46% vs 8% and splenomegaly (greater than 5 cm from LCM) in 50% vs 12% (P&lt;.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&lt;.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 &gt;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 &gt;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.

Background: Sodium-glucose co-transporter-2 inhibitors (SGLT-2I) are FDA-approved for diabetes mellitus, heart failure and chronic renal disease. Clinical trials on their anti-diabetic and cardiorenal protective effects showed an association with erythrocytosis. We have previously reported on the benign nature of SGLT-2I associated JAK2-unmutated erythrocytosis ( Blood 2021). Recently, we described the same phenomenon in the setting of a previously unrecognized myeloproliferative neoplasm (MPN), which led to unmasking of underlying MPN and thrombosis in 3 (33%) of 9 informative cases ( AJH 2023). The main objective of the current study was to assess the erythropoietic and thrombotic impact of SGLT-2I therapy in patients with a well-established MPN diagnosis, prior to treatment initiation. Methods: The Mayo Clinic MPN database was queried to identify patients prescribed SGLT2-I after diagnosis of essential thrombocythemia (ET), polycythemia vera (PV) or myelofibrosis (MF). Baseline Hgb/Hct at SGLT-2I initiation, peak Hgb/Hct, absolute change in Hgb/Hct levels, and thrombosis during treatment were recorded. Results: SGLT-2I use in essential thrombocythemia Eleven patients with ET (median age; 72 years, 55% males, 73% JAK2 mutated, 64% with thrombosis history) received SGLT-2I. Active treatments included aspirin ( n=10), cytoreductive therapy ( n=10) and systemic anticoagulation ( n=4). All 11 patients displayed increase in Hgb/Hct following SGLT-2I treatment. Baseline median (range) values for Hgb/Hct were 12.8 g/dL (9.5-14.9)/38.9% (30.3-44.6); median (range) peak Hgb/Hct levels during SGLT-2I therapy, were 14.5 g/dL (11-16.4)/44.4% (34.8-51.1), with median (range) increase in Hgb/Hct of 1.5 g/dL (1-4)/5.1% (2.6-13.8); 2 patients (18%), exceeded the proposed ICC Hgb/Hct diagnostic threshold for PV (Patient 7 and 8) (Figure 1). JAK2 mutation/VAF (p=0.54/ 0.20), or serum erythropoietin (Epo) (p=0.48) did not correlate with changes in Hgb/Hct levels. One patient experienced thrombosis, despite treatment with hydroxyurea and aspirin and Hgb/Hct levels below the threshold of concern (11.4 g/dL/37.7%). SGLT-2I use in polycythemia vera Nine patients with PV (median age 74 years, 66% males, JAK2 median VAF 14%, two patients with thrombosis history) received SGLT-2I. Concomitant treatments included aspirin ( n=9), cytoreductive therapy ( n=8), and systemic anticoagulation ( n=3). Phlebotomy intensity, defined as the number of phlebotomies, six months prior to and after SGLT-2I initiation, ranged from 0-3 and 0-12, respectively. Documented Hgb/Hct levels showed an increase in all 9 cases with baseline median (range) values for Hgb 14.1 g/dL (10.5-15.9) and Hct 42.7% (33.3-49.2) and peak median (range) values for Hgb/Hct, 15.4 g/dL (11.2-19.9)/46.7% (35.9-63.3). JAK2 VAF (p=0.85), and serum Epo (p=0.43) did not correlate with increase in Hct. Figure 2 highlights five patients (56%) with Hct exceeding 45% while on SGLT-2I; two patients (22%) had increased phlebotomy requirements; 6-month pre/post SGLT-2I phlebotomies for patient 5 and 9 were 3 and 6, and 0 and 12, respectively. Patient 9, experienced thrombosis in the context of uncontrolled Hgb/Hct level at 19.9 g/dl/63.3% and absence of cytoreductive therapy. SGLT-2I use in myelofibrosis Eight patients with myelofibrosis (primary 6, post-ET 2; median age 71 years; 50% males; 63% JAK2 mutated; MIPSS-70 2.0 int/high 6; on ruxolitinib 4),received SGLT-2I. Baseline median (range) values for Hgb/Hct were 10.6 g/dL (8.2-14.7)/27.5% (33.8-45.9); two (25%) patients displayed anemia with Hgb 8-10 g/dl. Peak median (range) values for Hgb/Hct were 11.5 g/dL (10.2-16.1)/35.3% (31.8-49.8), with median (range) baseline increase in Hgb/Hct of 1.6 g/dL (0.7-3.8)/4.3% (1-7.5). Patient 2 and 4 with baseline Hgb 8.2 g/dl and 9.4 g/dl, and not receiving ruxolitinib, had Hgb increase of 2 g/dl and 1 g/dl, respectively (Figure 3). One thrombotic event occurred during therapy with Hgb/Hct level of 11.6 g/dl/37.3%. Conclusion: The current study suggests that SGLT-2I therapy in MPN patients leads to increase in Hgb/Hct levels, regardless of disease subtype, and in some cases surpass the PV diagnosis and thrombosis risk thresholds. These observations mandate increased awareness to secure patient safety and diagnostic accuracy. The erythropoietic effect of SGLT-2I in MF suggests its potential use for MF-associated anemia.

Abstract We examined the individual prognostic contribution of absolute neutrophil (ANC), lymphocyte (ALC), and monocyte (AMC) counts, on overall (OS), leukemia‐free (LFS), and myelofibrosis‐free (MFFS) survival in essential thrombocythemia (ET). Informative cases ( N = 598; median age 59 years; females 62%) were retrospectively accrued from a Mayo Clinic database: JAK2 59%, CALR 27%, triple‐negative 11%, and MPL 3%; international prognostic scoring system for ET (IPSET) risk high 21%, intermediate 42%, and low 37%; 7% (37/515) had abnormal karyotype and 10% (21/205) adverse mutations ( SF3B1/SRSF2/U2AF1/TP53 ). At median 8.4 years, 163 (27%) deaths, 71 (12%) fibrotic, and 20 (3%) leukemic transformations were recorded. Multivariable analysis resulted in HR (95% CI) of 16.5 (9.9–27.4) for age > 70 years, 3.7 (2.3–6.0) for age 50–70 years, 2.4 (1.7–3.3) for ANC ≥8 × 10 9 /L, and 1.9 (1.4–2.6) for ALC <1.7 × 10 9 /L. The corresponding HR‐based scores were 4, 2, 1, and 1, resulting in an new 4‐tiered AgeAncAlc (AAA; triple A) risk model: high (5–6 points; median survival 8 years; HR 30.1, 95% CI 17.6–54), intermediate‐2 (4 points; median 13.5 years; HR 12.7, 95% CI 7.1–23.0), intermediate‐1 (2–3 points; median 20.7 years; HR 3.8, 95% CI 2.3–6.4) and low (0–1 points; median 47 years). The AAA model (Akaike Information Criterion [AIC] 621) performed better than IPSET (AIC 647) and was subsequently validated by an external University of Florence ET cohort ( N = 485). None of the AAA variables predicted LFS while ALC <1.7 × 10 9 /L was associated with inferior MFFS ( p = .01). Adverse mutations ( p < .01) and karyotype ( p < .01) displayed additional prognostic value without disqualifying the prognostic integrity of the AAA model. This study proposes a simple and globally applicable survival model for ET, which can be used as a platform for further molecular refinement. This study also suggests a potential role for immune‐related biomarkers, as a prognostic tool in myeloproliferative neoplasms.

Abstract Disease Overview JAK2 unmutated or non‐polycythemia vera (PV) erythrocytosis encompasses a heterogenous spectrum of hereditary and acquired entities. Diagnosis Foremost in the evaluation of erythrocytosis is the exclusion of PV through JAK2 (inclusive of exons 12–15) mutation screening. Initial assessment should also include gathering of previous records on hematocrit (Hct) and hemoglobin (Hgb) levels, in order to streamline the diagnostic process by first distinguishing longstanding from acquired erythrocytosis; subsequent subcategorization is facilitated by serum erythropoietin (Epo) measurement, germline mutation screening, and review of historical data, including comorbid conditions and medication list. Hereditary erythrocytosis constitutes the main culprit in the context of longstanding erythrocytosis, especially when associated with a positive family history. In this regard, a subnormal serum Epo level suggests EPO receptor mutation. Otherwise, considerations include those associated with decreased (high oxygen affinity Hgb variants, 2,3‐bisphosphoglycerate deficiency, PIEZO1 mutations, methemoglobinemia) or normal oxygen tension at 50% Hgb saturation (P50). The latter include germline oxygen sensing pathway ( HIF2A–PHD2–VHL ) and other rare mutations. Acquired erythrocytosis commonly results from central (e.g., cardiopulmonary disease, high‐altitude habitat) or peripheral (e.g., renal artery stenosis) hypoxia. Other noteworthy conditions associated with acquired erythrocytosis include Epo‐producing tumors (e.g., renal cell carcinoma, cerebral hemangioblastoma) and drugs (e.g., testosterone, erythropoiesis stimulating agents, sodium‐glucose cotransporter‐2 inhibitors). Idiopathic erythrocytosis is an ill‐defined terminology that presumes the existence of an increased Hgb/Hct level without an identifiable etiology. Such classification often lacks accounting for normal outliers and is marred by truncated diagnostic evaluation. Management Current consensus treatment guidelines are not supported by hard evidence and their value is further undermined by limited phenotypic characterization and unfounded concerns for thrombosis. We are of the opinion that cytoreductive therapy and indiscriminate use of phlebotomy should be avoided in the treatment of non‐clonal erythrocytosis. However, it is reasonable to consider therapeutic phlebotomy if one were to demonstrate value in symptom control, with frequency determined by symptoms rather than Hct level. In addition, cardiovascular risk optimization and low dose aspirin is often advised. Future Directions Advances in molecular hematology might result in better characterization of “idiopathic erythrocytosis” and expansion of the repertoire for germline mutations in hereditary erythrocytosis. Prospective controlled studies are needed to clarify potential pathology from JAK2 unmutated erythrocytosis, as well as to document the therapeutic value of phlebotomy.