Maccari, Chiara

Background: The JAK2 46/1, also referred to as the GGCC, haplotype, is represented by 4 main SNPs spanning a region of 250kb in chr9 including the JAK2 gene, that are in complete linkage disequilibrium. The GGCC haplo was found to confer susceptibility to JAK2 mutated myeloproliferative neoplasms (MPN) (Jones AV, 2009; Olcaydu D, 2009; Kilpivaara O, 2009) while association with JAK2-wildtype MPN remains controversial (Pardanani A, 2010; Jones AV, 2010; Guglielmelli P, 2010; Trifa A, 2016). The GGCC haplo was also found enriched in MPN pts with splancnic vein thrombosis (SVT) (Smalberg JH, 2011), and to correlate with higher JAK2V617F variant allele frequency (VAF) (Alvarez-Larran, A, 2012). Nullizigosity for GGCC haplo was associated with reduced survival (OS) in pts with myelofibrosis (MF) (Tefferi A, 2019), but no information on the impact of GGCC haplo status with phenotype and outcome in PV is available. Aim: To assess the clinical correlates and the prognostic significance of GGCC haplo status in a large cohort of pts with PV. Pts and Methods: A total of 399 PV pts, all JAK2V617F mutated, diagnosis revised according to 2022 ICC criteria, were genotyped for 46/1 haplotype by PCR allele discrimination with rs12343867 (with the “C” allele standing for 46/1 haplotype). Results: A total of 301 pts (75.4%) had the C allele, of which 143 (47.5%) were CC homo and 158 (52.5%) CT hetero; 98 (24.6%) were nullizygous for GGCC (TT). Since preliminary analysis disclosed no significant difference between CT and TT haplotype for all variables considered, homozygous CC pts were compared to TT+CT. The CC haplotype was associated with higher leukocytes (median 11.3x10e9/L vs 9.6, p<.001), higher hemoglobin (18.4 g/dL vs 17.5, p<.001), lower platelets (441x10e9/L vs 514, p=.002) more aquagenic pruritus (51.8% vs 33.2%, p=.001), and higher JAK2VAF (60.8+-24.8% vs 36.8+-19.7%, p<.001) at diagnosis. Pts with a VAF >50% were 69% in CC versus 24.1% in TT+CT pts (p<.001). ASXL1 mutations were enriched among CC pts (20.3% vs 9.4%, p=0.04), otherwise no difference regarding additional myeloid mutations was noted. All above differences remained significant when considering CC versus TT and CT separately. More pts with CC haplotype suffered from venous thrombosis (VT) during the FU (16.1% vs 4.3%, p<.001), no difference was noted for arterial thrombosis nor for splancnic vein thrombosis. VT-FS by Kaplan Meyer was significantly shorter (p<.001) in CC pts; the rate of VT at 5, 10, 15y after diagnosis, was 5.5%, 12%, 20.2% for CC versus 2.6%, 3.4%, 6.4% for TT+CT, respectively (all p<.001). In multivariable analysis, including JAK2VAF >50%, age >60y, history of VT, WBC >15x10e9/L, only CC haplo remained significant (HR 3.6, 95%CI 1.4-9.5, p=.009). Progression to post-PV MF occurred in 81 pts (20.3%), significantly more among CC (n=45, 31.5%) than TT+CT (n=36; 14.1%; p<.001). Myelofibrosis-FS was significantly shorter in CC vs other genotypes (p=.02). However, in multivariable analysis, only BM fibrosis G1 remained significant (HR 3.2, 1.7-5.9; p<.001). Evolution to blast-phase occurred in 13 pts (3.2%), 9 (6.3%) with CC haplo vs 4 TT+CT (1.6%; p=.01). During the follow-up, 102 pts (25.5%) died, 50 (35%) CC and 52 TT+CT (20.3%; p=.001). In multivariable analysis, including MIPSS-PV variables (Tefferi A 2020), the CC haplo remained significant (HR 1.8, 1.04-3.2, p=.03) together with age (HR 3.0, 1.6-5.7; p<.001), WBC (HR 2.6, 1.3-4.8; p=.004), and thrombosis history (HR 1.9, 1.0-3.7; p=.03). Conclusions. Homozygosity for the 46/1 or CC haplotype contributes to the phenotype diversity of PV, in part possibly mediated by associated higher JAK2V67F VAF, and predicts for incident VT and shorter OS. Supported by AIRC, 21267; MIUR,2022F4WMR3; IHM, PNRR-MAD-2022-12376695

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: In addition to the driver mutations JAK2, CALR and MPL, patients (pts) with primary myelofibrosis (PMF) may also express mutations in a number of genes frequently associated with myeloid neoplasms. These genes encode regulators of chromatin modification and DNA methylation, RNA splicing and transcription, as well as oncogenes and signal transduction. In pts with PMF, including those with prefibrotic (pre-)-PMF, selected mutations were shown to deserve prognostic relevance, and led to the development of molecular integrated, or exclusive, scores (such as MIPSS70, MIPSS70-plus, GIPSS and others). Aim: The aim of the study was to correlate the type of mutations, clustered in relation to their known functional classes, with hematological and clinical correlates, and outcome in a large population of molecularly annotated pts with PMF. Patients and Methods: All pts with a confirmed ICC 2022 diagnosis of PMF from the database at CRIMM (Florence), for whom mutation analysis of a panel of 40 myeloid neoplasm-associated genes performed by NGS (Oncomine, ThermoFisher) was available, were included in the study. Pts were stratified in 6 categories based on known function of mutated gene: spliceosome (cat. 1: SF3B1, U2AF1, SRSF2, ZRSR2), DNA methylation gene (cat. 2: TET2, DNMT3A, IDH1, IDH2, SETBP1), histone modification gene (cat. 3: ASXL1, EZH2), RAS pathway (cat. 4: NRAS, KRAS, CBL, NF1, PTPN11), transcription factor (cat. 5: RUNX1, NFE2, TP53) and “other” gene mutations (cat. 6: LNK/SH2B3). Results: A total of 286 pts with at least 1 myeloid neoplasm-associated gene mutation were included (110 prePMF, 38.5%; 176 overt PMF, 61.5%). Of these, 69 have mutations in spliceosome genes, 81 in DNA methylation genes, 95 in histone modification genes, 19 in the RAS pathway, 13 in transcription factor genes and 9 in “other” gene category. Analysis of clinical characteristics (Table) showed that Cat. 1 pts were significantly older (80.6% aged >60y, P=0.003), no difference regarding gender. There was no difference in blood counts but circulating blasts >1%, that were higher in cat 3 and 1 compared to the others (P=0.009). A G3 fibrosis was more common in cat 3 and 5 (43.5% and 50%, p<0.001). No significant difference was noticed as regarded driver mutations and karyotype abnormalities. Splenomegaly was more common in cat 3 and cat 6 (86.5% and 88.9%, respectively, p=0.015), while constitutional symptoms were enriched in cat 5 (69.2%, p=0.015). The proportion of pts with transfusion dependency was lower among those with mutations in DNA methylation genes (cat. 2) and “other” mutations (cat. 6) (21% and 22.2%, respectively, p=0.014). There was no significant difference among gene categories as regarded IPSS score, MIPSS70 score, thrombosis and bleeding events, progression to overt MF (in case of pre-PMF), transformation to AML and rate of secondary neoplasms. The median overall survival (OS) for all pts was 7.1 years (IC: 5.7-8.5), with categories 2, 4 and 5 showing the longest survival (10.7y (6.3-15.1), 11.5y (4.4-18.7), and 10.5y (2-18.9) respectively). In particular, pts in cat 2 showed significantly longer OS than pts in cat 1 (5.4y; HR 1.7, 95% CI, 1.1-2.6; p=0.021) and cat 3 (10.7 vs 6.1y; HR 1.5, 95% CI, 1-2.3). Considering that cat 1, 3, and 6 on one side, and cat 2, 4, 5 on the other, did not differ significant each to the other, we combined those categories to assess respective impact on survival. We found a statistically significant difference between the 2 groups, with pts harboring mutations in spliceosome, histone modifiers and “other” genes having significantly shortened survival (5.8y, CI 4.1-7.5; HR 1.57, CI 1.13-2.18) compared to the other categories (median survival, 10.8y, CI 7.2-14.3) (P=.007). Conclusion: Current analysis revealed distinctive clinical characteristics and survival outcomes associated with specific categories of mutated myeloid genes in pts with PMF, largely overlapping with the ICC defined “myelodysplasia-related gene mutations” category.

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.

Abstract Background: Thrombosis is the main cause of morbidity and mortality in pts with Polycythemia Vera (PV). Current risk stratification is based on 2 variables: age >60y and history of thrombosis. Additional thrombotic risk factors in PV are generic cardiovascular risk factors and leukocytosis. JAK2V617F (JAK2VF) variant allele frequency (VAF) at diagnosis is highly heterogeneous. A VAF>75% was associated with higher rate of all thrombosis after diagnosis (Vannucchi AM et al, Leukemia 2007), and a VAF ≥ 60% correlated with increased rate of venous thrombosis (VT) in high-risk pts (Guglielmelli P et al, ASH 2018); however, predictive role of JAK2VF VAF is still debated. Aim: To evaluate the impact of JAK2VF VAF on rate of arterial and venous thrombosis in PV pts. Patients and methods: A cohort of 576 strictly 2016 WHO-defined PV pts followed at Univ. of Florence (1981-2020) were included. All pts were annotated for JAK2VF VAF, determined <3 years from diagnosis, and thrombosis at diagnosis and follow-up (FU). Arterial thromboses (AT) included stroke, transient ischemic attacks, retinal artery occlusion, coronary artery disease, and peripheral arterial disease; VT included cerebral venous thrombosis, deep vein thrombosis, pulmonary embolism. Splanchnic vein thromboses (SVT) were excluded. Only first occurring event was considered. Cox proportional hazard regression model was used for univariate and multivariable analysis. Kaplan-Meier (KM) analysis was used for time-to-event assessment, compared by log-rank test. Results: Median age was 61.4 y (range, 16.2-91.8), 58.2% were male; 62% were high-risk based on current classification. Median JAK2VF VAF was 41.5% (range, 0.3-100). A total of 76 (13.2%) pts had an AT event before/at PV diagnosis and 49 (8.5%) pts had an AT during FU. As regards VT, 64 (11.1%) and 39 (6.8%) pts had a VT before/at or after PV diagnosis, respectively. We found that JAK2 VAF as a continue variable was correlated with the risk of VT in FU (p=0.003) but not with AT (p=0.8). ROC analysis to determine the best cut-off level for JAK2 VAF predicting VT had an AUC of 0.72 and a best cut-off value of VAF=50%. VT at FU were significantly enriched in pts with VAF >50%: 14.5% versus 2.4%, p=<0.0001. VT -free survival (VT-FS) by KM was significantly shorter in the presence of a JAK2 VAF >50% (HR 4, CI 1.9-8.6, p<0.0001) (Figure 1A), whereas no difference was found for AT (HR 0.9). In addition to JAK2VF VAF>50%, univariate analysis for VT-FS identified history of VT (HR 2.9; CI 1.4-6.1, p=0.006), leukocytosis ≥11x10 9/L (HR 1.9; CI 1.1-3.4, p=0.02) and palpable splenomegaly (HR 1.9, CI 1-3.6; p=0.04) as risk factors. Multivariable analysis confirmed VAF>50% (HR 3.8, CI 1.8-8.1, p=0.0006) and previous VT (HR 2.4, CI 1.1-5.1; p=0.02) as independent risk factors for future VT. In contrast, univariate analysis for AT-free survival (AT-FS) identified history of AT (HR 2.5; CI 1.3-4.9, p=0.007), diabetes (HR 3.3; CI 1.6-6.5, p=0.0007), hyperlipidemia (HR 3.1; CI 1.7-5.6, p=0.0003) and hypertension (HR 2, CI 1.1-3.8; p=0.03) as predictors of future AT; age >60y showed only a trend (p=0.08). Multivariable analysis for AT-FS identified diabetes (HR 2.4, CI 1.2-5; p=0.02), hyperlipidemia (HR 2.3; CI 1.2-4.3, p=0.01) and previous AT (HR 2.1, CI 1-4.2; p=0.04) as independent predictors of future AT. Validation: Our findings were validated in an independent cohort of 315 2016-WHO defined PV pts from Policlinico Gemelli, Catholic Univ., Rome. After exclusion of 26 pts with SVT, analysis was conducted on 289 pts, 38 of them with thrombosis as heralding event (21 AT and 17 VT). Multivariable analysis confirmed JAK2VF VAF >50% (HR 2.3, CI 1.03-5.0, p=0.04) and previous VT (HR 4.5, CI 2.0-10.1; p=0.0003) as independent risk factors for future VT. In pts with VAF >50%, the rate of VT at FU was 19.9% vs 7.7%, P=0.005. KM curve showed that VT-FS was significantly shorter in pts with a JAK2VF VAF >50% (HR 2.2, CI 1.2-4.2; p=0.01) (Figure 1B). Of note, impact of JAK2 VAF>50% on VT at FU was statistically significant particularly in conventionally low-risk pts, accounting for an HR of 9.4 (CI 1.2-72) and HR 3.6 (CI 1.3-10) in Florence and Rome cohorts, respectively. Conclusions: These data support JAK2VF VAF as a strong independent predictor for future venous thrombosis in PV, in association with history of prior venous events, reinforcing that AT and VT are associated with unique risk factors in pts with PV. Supported by AIRC, Project Mynerva n.21267 Figure 1 Figure 1. Disclosures Vannucchi: BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees.

Abstract Introduction: Myelofibrosis -either primary (PMF) or post-polycythemia vera/essential thrombocythemia (collectively, secondary MF [SMF])- is characterized by biologic and clinical heterogeneity, with some patients (pts) presenting with features of myeloproliferation (MyP) and others exhibiting a myelodepletive (MyD) phenotype. Although not well defined, the latter is marked by cytopenias involving one or more hematopoietic lineages, in some respects mimicking a myelodysplastic or bone marrow (BM) failure syndrome. MyD features have been associated with poor prognosis in patients with MF, but cytopenias have been usually considered individually. In the current study, we aimed at investigating the phenotypic and prognostic correlates of a MyD phenotype in a large cohort of MF patients. Methods: After IRB approval, 704 consecutive patients with WHO-defined MF referring to CRIMM (Florence), were included in the study. There were 442 (63%) PMF and 262 (37%) SMF. Cytopenias at diagnosis were defined as follows: white blood cell (WBC) <4×10 9/L, hemoglobin (Hb) <11 g/dL for male and <10 g/dL for female, platelets (Plt) <100×10 9/L. A MyD phenotype was defined by the presence of at least one cytopenia in the absence of any increase of other blood cells (WBC >15×10 9/L, Hb >16.5 g/dL for male and >16 g/dL for female, Plt >450×10 9/L). Pts not included in the MyD group were considered as having a MyP phenotype. Mutational analysis by targeted NGS was available for 594/704 patients (PMF 368/442; SMF 226/262). Results: Overall, 166 pts were diagnosed as having a MyD MF, including 108 (24%) PMF and 58 (22%) SMF. Among PMF patients, leukopenia, sex-adjusted anemia and thrombocytopenia were present in 38%, 84% and 35%, respectively; in SMF, corresponding figures were 24%, 91% and 24%. Two or more cytopenias were found in 11% and 6% of PMF and SMF patients, respectively. In PMF, a MyD phenotype was associated with male gender (P=.0468), older age (P=.0002), lower peripheral blast count (P=.0006), higher prevalence of splenomegaly (P=0.0142), constitutional symptoms (P<.0001), and BM fibrosis grade ≥2 (P<.0001). The rates of thrombosis and bleeding were not different compared to MyP PMF. MyD pts were more likely to have very high risk (VHR) karyotype abnormalities (P=.0002) and to be triple negative (TN; P<.0001); there were no correlations with JAK2 mutation status and mutant burden, CALR and MPL mutations. Among non-driver mutations, a MyD phenotype was significantly enriched in ASXL1 (P=.0074), IDH1/2 (P=0.064), N/KRAS (P=.0014), U2AF1 (P<.0001), and CUX1 (P=.0002) mutations. Karyotype abnormalities (P=.0084), VHR cytogenetics (P=.0343), CBL (P=.0.171) and U2AF1 (P=.0148) mutations were significantly enriched in MyD pts with ≥2 cytopenias. On univariate analysis, OS was significantly shorter in pts with MyD vs MyP PMF (median, 55 vs 103 months, respectively; P<.0001), and not different between MyD pts with one (median, 65 months) and ≥2 (median, 44 months) cytopenias (Fig. 1A). After competing risk analysis, the cumulative incidence of leukemic transformation (LT) was not different between MyD and MyP phenotypes (16% vs 11% at 5 years, respectively). Phenotypic differences between MyD and MyP patients were less evident in SMF, a part for older age of the former (P=.0207). The molecular background was likewise different: a MyD feature was enriched in mutations in TP53 (P=.0024), U2AF1 (P<.0001), and SETBP1 (P=.0125). TP53 mutations were remarkably more frequent in MyD SMF pts with ≥2 cytopenias (19%). Pts with MyD SMF had a significantly shorter OS compared to the MyP counterpart (median, 44 vs 105 months; P<.0001). Median OS was significantly inferior in MyD patients with ≥2 cytopenias compared to one cytopenia (median, 27 vs 58 months, respectively; P<.0001) (Fig. 1B). The cumulative incidence of LT was not different: 16% vs 7% at 5 years, respectively, for SMF pts with MyD and MyP phenotype. Conclusion: The current study provides a comprehensive analysis of the MyD phenotype in pts with PMF and SMF, partly recapitulating findings of previous studies (Marcellino BK et al. Clin Lymphoma Myeloma Leuk 2020). We showed that the MyD phenotype is associated with high-risk clinical and molecular features, particularly in PMF, and correlates with inferior OS. Of interest, U2AF1 mutations emerged as a distinct molecular marker of MyD in both PMF and SMF, while mutations in TP53 appear prevalent in MyD SMF. Figure 1 Figure 1. Disclosures Vannucchi: Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees.

Abstract The current retrospective study involving a total of 1607 patients was designed to identify clinical and molecular variables that were predictive of inferior myelofibrosis‐free survival (MFS) in WHO‐defined essential thrombocythemia (ET), utilizing three independent patient cohorts: University of Florence, Italy ( n = 718); Mayo Clinic, USA ( n = 479) and Policlinico Gemelli, Catholic University, Rome, Italy ( n = 410). The Florence patient cohort was first examined to identify independent risk factors for MFS, which included age > 60 years (HR 2.5, 95% CI 1.3–4.9), male sex (2.1, 1.2–3.9), palpable splenomegaly (2.1, 1.2–3.9), CALR 1/1‐like or MPL mutation (3.4, 1.9–6.1) and JAK2 V617F variant allele frequency > 35% (4.2, 1.6–10.8). Subsequently, an operational molecular risk category was developed and validated in the other two cohorts from Mayo Clinic and Rome: “high molecular risk” category included patients with JAK2 V617F VAF >35%, CALR type 1/1‐like or MPL mutations; all other driver mutation profiles were assigned to “low molecular risk” category. The former, compared to the latter molecular risk category, displayed significantly higher risk of fibrotic transformation: Florence cohort with respective fibrotic transformation risk rates of 8% vs. 1.2% at 10 years and 33% vs. 8% at 20 years ( p < 0.001; HR 6.1; 95% CI 3.2–11.7); Mayo Cohort, 16% vs. 7% at 10 years and 44% vs. 25% at 20 years ( p < 0.001; HR 2.5; 95% CI 1.6–4.1); and Rome cohort 7.8% vs. 4.6% at 10 years and 31.2% vs. 7.1% at 20 years ( p = 0.007, HR 2.7; 95% CI 1.3–5.8). The present study provides practically useful risk signals for fibrotic transformation in ET and facilitates identification of patients who require close monitoring and appropriate counseling.