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Myeloproliferative neoplasm (MPN) patients are at risk of splanchnic vein thromboses (SVT). Prior studies have failed to demonstrate a benefit of hydroxyurea therapy in preventing recurrent thrombosis after SVT, but are limited by small sample sizes and inability to account for starting, stopping, or switching of cytoreductive therapies. To better assess the impact of cytoreductive therapy on thrombosis recurrence, we performed a retrospective cohort study of MPN-SVT patients from the international GASTRO-MPN Consortium, treating cytoreductive therapy as a time-dependent covariate. We identified 757 patients, of which 43% were treated with cytoreductive therapy. During a median follow-up of 7.4 years, 256 patients (34%) had thrombosis recurrence; 145 (19%) had SVT extension/recurrence/TIPS thrombosis, 138 (18%) an thrombosis recurrence outside the splanchnic bed (74% were venous). Additionally, 262 patients (35%) experienced clinically relevant bleeding and 170 (22%) died. After adjusting for age, sex, prior thrombosis, timing of MPN diagnosis relative to SVT, anticoagulation initiation within 30 days of SVT diagnosis, MPN type, JAK2 status, other cancers and cirrhosis, cytoreductive therapy was associated with a decreased risk of recurrent thrombosis (HR 0.67 95%CI 0.50-0.89, p=0.01). This was driven by a lower risk of SVT extension/recurrence (HR 0.62 95%CI 0.42-0.90, p=0.01) but not by extra-splanchnic thrombosis recurrence (HR 0.97 95%CI 0.72-1.30, p=0.82). In a subgroup of patients without erythrocytosis/thrombocytosis at initial SVT (n=275), cytoreductive therapy was associated with a HR 0.65 (95%CI 0.40-1.07, p=0.09) for recurrent thrombosis. These data support the use of cytoreductive therapy in MPN-SVT patients to prevent recurrent thrombosis, particularly SVT extension/recurrence.

Abstract Background A previous multicenter study of patients with TP53-mutated myeloproliferative neoplasms showed a significantly shorter survival in chronic phase myelofibrosis (MF-CP) that included primary (PMF) and secondary MF and was mostly based on research-based mutation screening and was not systematically controlled for patients without TP53 mutations (AJH 2025;100:552). The objective of the current study was to examine the prognostic impact of TP53 mutations (VAF ≥2%) that were discovered during clinical NGS testing among consecutive patients with PMF-CP. Impact on overall (OS) and leukemia-free (LFS) survival was analyzed in the context of other genetic risk factors and calculated from the time of mutation detection. Methods The current retrospective study includes consecutive patients with PMF-CP who underwent clinical NGS testing at the Mayo Clinic between 2015 and 2025. Diagnoses of PMF-CP and leukemic transformation (LT) were retrospectively fitted to be in accordance with the International Consensus Classification criteria (Blood 2022;140:1200). Mutation and cytogenetic analyses were performed according to institutional protocols for clinical use and reported in conformity with international guidelines. OS and LFS analyses were censored for treatment with allogeneic stem cell transplantation (ASCT) and calculated from the date of NGS. Conventional statistical methods were utilized (JMP Pro 17.1.0, SAS Institute, Cary, NC, USA). Results A total of 633 patients with PMF-CP underwent clinical NGS testing prior to LT and prior to ASCT (median age 65 years; males 59%). Median interval from initial diagnosis/referral to NGS testing was 2 months; 357 (56%), 392 (62%), and 429 (68%) patients had NGS performed within 3, 6 and 12 months of diagnosis, respectively. Risk distribution according to the dynamic International Prognostic Scoring System (DIPSS; Blood 2010;115:1703) were low (19%), intermediate-1 (44%), intermediate-2 (31%), or high (6%). TP53 mutations (TP53MUT) with variant allele frequency (VAF) of ≥2% were detected in 28 (4.4%) patients with a median VAF of 25.3% (range 2.4-85; ICC-defined multihit 43%). Patients with TP53MUT were more likely to harbor IDH2MUT (14% vs. 3%; p<0.01), EZH2MUT (14% vs. 4%; p=0.03), and unfavorable karyotype (36% vs. 19%; p=0.047) and less likely to harbor CALR type 1/like (4% vs. 18%; p=0.02) and SF3B1MUT (0% vs. 6%; p=0.07). The association with unfavorable karyotype was mainly driven by multihit configuration. No significant associations with clinical features were apparent. At a median follow-up of 40 months for surviving patients, 157 (25%) deaths, 48 (8%) LTs and 135 (21%) ASCTs were documented. A near-two-fold lower, albeit not statistically significant OS was observed in the presence of TP53MUT (median 123 vs. 228 months; HR 1.9, 95% CI 0.94-3.7; p=0.074); the difference reached significance for multihit TP53MUT (median 81 months; HR 3.6, 1.7-7.7; p<0.01) but not for non-multihit TP53MUT (median not reached; HR 0.7, 0.2-2.8; p=0.6), both compared to TP53WT (median 228 months). The significant impact of multihit TP53MUT on OS was confirmed in multivariable analysis (MVA) that included other high molecular risk (HMR) mutations and unfavorable karyotype: multihit TP53MUT (HR 2.5, 1.1-5.5; p=0.02), SRSF2MUT (2.4, 1.5-3.8; p<0.01), ASXL1MUT (1.8, 1.2-2.6; p<0.01), U2AF1MUT-Q157 (4.8, 2.6-8.6; p<0.01), and absence of CALR type 1/like (4.0, 2.0-7.8; p<0.01); additional prognostic contribution was not evident for unfavorable karyotype (p=0.17), EZH2MUT (p=0.3), IDH1MUT (p=0.6), IDH2MUT (p=0.7), or any other HMR mutation. Multihit TP53MUT was also associated with inferior LFS (10-year risk 62% vs. 32% for non-multihit TP53MUT vs. 15% for TP53WT; p=0.03) but significance was lost during MVA that included SRSF2MUT, which was the only HMR mutation showing a significant effect on LFS (HR 5.0, 2.5-9.8; p<0.01). Post-ASCT survival among 135 transplanted patients was significantly shorter for patients with multihit TP53MUT (N=4; median 5 months) vs. those with non-multihit TP53MUT (N=7; median not reached) vs. patients with TP53WT (N=124; median not reached) [p=0.02]. Conclusion The current study implicates multihit TP53MUT as an HMR mutation-independent prognostic factor for OS in PMF-CP. By contrast, prognosis in PMF-CP patients with non-multihit TP53MUT was more likely to be influenced by other HMR mutations, as was the case for those with TP53WT.

Abstract Background Myeloproliferative neoplasms (MPNs) can progress from chronic phase to accelerated or blast phase (MPN-AP/BP), a transition with poor prognosis and limited treatment options. While some abnormalities have been described, the genomic and clonal drivers of transformation remain poorly defined. We characterized mutational and structural alterations in MPN-AP/BP, leveraging paired samples to trace clonal evolution. Methods We profiled 186 samples from 160 individuals, including 159 MPN-AP/BP and 27 chronic-phase MPN samples (26 MF, 1 PV), using targeted sequencing of a 588 gene panel (mean depth: 709x). Paired pre- and post-transformation samples were available for 26 patients (n= 52). A consensus pipeline was used to detect somatic mutations, copy number variations (CNVs), and copy-neutral loss of heterozygosity (cnLOH). Clinical cytogenetic data were integrated when available. Single-cell validation is ongoing. Results Genomic complexity was widespread: 99% of patients harbored ≥1 oncogenic mutation (median 4; range 1–10). In total, 859 mutations were identified, most commonly in JAK2 (68%), ASXL1 (28%), TET2 (26%), SRSF2 (24%), TP53 (22%), and RUNX1 (22%). 684 structural alterations were identified in 86% of patients (median 3; range 1-20), including arm-level (22.5%), segmental (>5 Mb; 60%), and focal (<2 Mb; 9%) alterations. Recurrent events included 9p cnLOH (16%), del(5q) (13%), del(17p) (10%), and focal deletion of 21q22.12 involving RUNX1 (10%). Complex karyotypes (≥3 abnormalities) were observed in 55% of patients. Biallelic mutations accounted for 21% (183/859) of mutations, affecting 58% of patients across 21 genes, most frequently JAK2 V617F (28%), TP53 (17%) and TET2 (14%). Patients with biallelic mutations in these genes had significantly higher blast percentages compared to those with monoallelic mutations (p<0.05), highlighting an association with aggressive disease. In 26 patients with longitudinal samples (chronic phase MPN and MPN-AP/BP), 87% (125/144) of mutations were already detectable during the chronic phase, on average more than 7 years prior to transformation. Only 11% (16/144) of mutations were newly acquired, including additional RUNX1 and TP53 hits, or structural changes that converted pre-existing JAK2 V617F and TP53 R248Q mutations from monoallelic to biallelic via 9p cnLOH or 17p loss, respectively. These findings suggest transformation is often driven by outgrowth of pre-existing high-risk clones, indicating that these clones likely have a competitive advantage and that the mutations within these clones have a cooperative biological interaction which underlies this competitive advantage. To investigate this hypothesis, we examined whether patterns of recurrent co-mutations were identifiable in this cohort. We identified recurrent co-occurring mutations in SRSF2-IDH2, ASXL1-SRSF2, and ASXL1-EZH2, which were enriched at transformation (p < 0.05; Fisher exact test). Importantly, presence of these co-mutations was consistently associated with a higher transformation risk in two independent cohorts of MF patients from Mayo Clinic (n= 405) and University of Florence (n= 518). Clonal architecture analysis revealed that these co-mutations frequently arose within the same malignant clone: 100% for SRSF2-IDH2, 80% for ASXL1-SRSF2, and 85% for ASXL1-EZH2, and are often within the dominant clone. Prior studies have demonstrated mechanistic interplay between SRSF2 and IDH2 (Yoshimi et al.), as well as ASXL1 and SRSF2 (Sui et al.) mutations in myeloid malignancies. We assessed functional synergy of ASXL1-EZH2 using a murine model and identified that dual deletion caused a rapidly fatal myeloid neoplasm with shorter survival than single-gene loss. These results reinforce that functional synergy emerges within a shared cellular context, supporting clonal co-dependence as a driver of progression. Single-cell RNA sequencing of ASXL1-EZH2 mutant cases is ongoing and will be presented. Conclusions Transformation to MPN-AP/BP is driven by gradual clonal remodeling and expansion of pre-existing high-risk abnormalities. Biallelic and multi-hit alterations in TP53, JAK2, TET2, and RUNX1 promote clonal dominance and blast progression. Recurrent co-mutations such as IDH2-SRSF2 and ASXL1-EZH2 arise within the same clone, exhibit functional synergy, and are linked to poor outcomes. These findings support the clinical utility of early clonal and co-mutational profiling to guide risk-adapted intervention.

Abstract Background Patients with myeloproliferative neoplasms (MPNs) are at risk of splanchnic vein thrombosis (SVT). Prior studies failed to demonstrate a benefit of hydroxyurea in preventing SVT extension/recurrence, but these were limited by small sample sizes and inability to account for starting, stopping, or switching of cytoreductive therapies. We therefore investigated the role of cytoreduction as a time-dependent covariate on thrombosis recurrence in a large, international cohort of MPN-SVT patients. Methods We performed a retrospective cohort study of MPN-SVT patients included in the international GASTRO-MPN consortium. Patients diagnosed with MPN at any time before, concurrently with, or up to 60 days after initial SVT were included. Primary outcome was time from initial SVT to first thrombosis recurrence, defined as the composite of SVT extension/recurrence, transjugular intrahepatic portosystemic shunt (TIPS) thrombosis, or venous/arterial thrombosis outside the splanchnic veins. Secondary outcomes included SVT extension/recurrence, TIPS thrombosis or extra-SVT thrombosis individually, clinically relevant bleeding (composite of major and clinically relevant non-major bleeding), MPN progression to myelofibrosis or blast phase, and death. Cytoreductive therapy was treated as a time-dependent covariate to account for discontinuation and therapy changes. Multivariable Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CI). Results A total of 757 patients were included for this analysis. Median age was 51 years (IQR 38-62), 59% were female. SVT involved the portomesenteric veins in 558 (77%) patients, hepatic veins in 95 (13%), and both in 54 (7.4%). MPN was known prior to initial SVT in 316 patients (42%) and diagnosed concurrently or up to 60 days after SVT in 441 (58%). Polycythemia vera (PV) was the most common MPN subtype (43%), followed by essential thrombocythemia (ET) in 24%, and primary myelofibrosis in 14%. JAK2V617F mutation was present in 86% and CALR in 2.9%. 13% had prior non-SVT thrombosis. 607 patients (83%) were treated with cytoreduction. At time of SVT, 131 patients (17%) were already on cytoreduction; in those who started after SVT, median time to initiation was 54 days after SVT, and median duration of cytoreduction per patient was 63 months. Cytoreductive therapies used at any point in treatment included hydroxyurea in 504 (69%), ruxolitinib in 182 (25%), and interferon-based in 85 (12%) patients. Anticoagulation (AC) was started within 30 days after SVT in 504 (68%) patients. Median duration of any AC per patient was 24.6 months. During a median follow up of 7.4 years, 245 patients (33%) had thrombosis recurrence; 143 (20%) had SVT extension/recurrence/TIPS thrombosis, 129 (18%) extra-SVT thrombosis (of which 74% venous), 237 patients (32%) experienced clinically relevant bleeding, and 163 (22%) died. After adjusting for age, sex, timing of MPN diagnosis relative to SVT diagnosis, AC within 30 days of SVT, PV/ET vs other MPN, JAK2 mutation, previous thrombosis, non-MPN cancer, and cirrhosis, cytoreductive therapy was associated with a significantly decreased risk of recurrent thrombosis (HR 0.67 95%CI 0.50-0.89, p=0.01). Age was associated with an increased risk of recurrent thrombosis (p=0.01). When considering types of recurrent thrombosis, cytoreduction was associated with a decreased risk of SVT extension/recurrence/TIPS thrombosis (HR 0.62 95%CI 0.42-0.90, p=0.01), but not thrombosis outside the splanchnic veins (HR 0.97 95%CI 0.72-1.30, p=0.82). There was no association between cytoreduction and bleeding (HR 1.10 95%CI 0.82-1.47, p=0.52). Similarly, there was no association between cytoreduction and time to MPN progression (p=0.24) or overall survival (p=0.30). In a subgroup of patients without erythrocytosis/thrombocytosis at initial SVT (n=271), cytoreductive therapy was associated with a HR 0.65 (95%CI 0.40-1.10, p=0.09) for recurrent thrombosis. Limited sample size and low event-rate precluded evaluation of the impact of individual cytoreductive therapies. Conclusions In the largest cohort of MPN-SVT patients to date, we show for the first time that cytoreductive therapy is associated with a decreased risk of thrombosis recurrence, driven largely by decreased SVT extension/recurrence/TIPS thrombosis. Collectively, these findings support use of cytoreductive therapy in individuals with MPN-SVT to prevent recurrent thrombosis.

Abstract Background: The International Prognostic Scoring System (IPSS; Cervantes et al. Blood 2009;113) and dynamic IPSS (DIPSS; Passamonti et al. Blood 2010;115:1703) were developed about 15 years ago, based on 5 clinical risk factors: age >65 years, hemoglobin <10 g/dl, white blood cell count (WBC) >25 x 109/L, peripheral blood (PB) blasts ³1%, and constitutional symptoms. DIPSS-independent genetic risk factors have since been incorporated into molecular risk models with higher predictive accuracy (Guglielmelli et al. JCO 2018;36:310; Tefferi et al JCO 2018;36:1769). Because of its accessibility, DIPSS is often preferred for use in patient selection for clinical trials. The objective of the current study was to revise DIPSS by incorporating new and refined clinical risk variables and excluding those that are subjective (e.g., symptoms) or could exaggerate the need for therapy for older adults (e.g., age). Methods: Diagnostic criteria were according to the International Consensus Classification (Arber et al. Blood 2022; 140:1200). Severity of anemia was adjudicated by the Revised International Working Group-European LeukemiaNet criteria (Blood 2024; 144:1813). Receiver operating characteristic curve analysis was utilized to determine the optimal cutoff points for age, WBC, PB blast percentage, absolute monocyte count (AMC), and platelet count. Data were collected retrospectively corresponding to the time of first referral, which, in the majority of cases, coincided within one year of initial diagnosis and before initiation of cytoreductive therapy. Survival analysis was censored for allogenic stem cell transplantation (ASCT). Time-specific AUC was computed at pre-defined landmark time points and used to compare model performance between DIPSS and the revised model (DIPSS-R). Results: The discovery cohort from the Mayo Clinic included 1,073 patients (median age 65 years; 61% males) and the validation cohort from Italy 635 patients (median age 63 years; 60% males). In the discovery cohort, median follow-up (% deaths, AML, ASCTs) was 45 months (49%, 10%, 17%) and in the validation cohort 60 months (42%, 11%, 5%). In univariate analysis, the following correlated with inferior survival, in both the discovery and validation cohorts, with significance confirmed by multivariable analysis (MVA) in the discovery cohort: severe anemia (transfusion-dependent or hemoglobin level <8 g/dL in women or <9 g/dL in men), moderate anemia (hemoglobin level 8 to <10 in women or 9 to <11 in men), marked leukocytosis (WBC ≥25 x 109/L), moderate leukocytosis (WBC 11 to <25 x 109/L), age >65 years, PB blast ≥2%, AMC ≥1 x 109/L, platelet count <150 x 109/L, constitutional symptoms, and male sex. After excluding age, sex, and constitutional symptoms, MVA-derived HRs (95% CI) were 3.5 (2.8-4.4) for severe anemia, 2.0 (1.5-2.5) moderate anemia, 2.4 (1.8-3.3) marked leukocytosis, 1.5 (1.2-1.9) moderate leukocytosis, 1.7 (1.4-2.1) PB blast ≥2%, 1.5 (1.2-2.0) AMC ≥1 x 109/L, and 1.5 (1.2-1.8) platelet count <150 x 109/L. An HR-weighted risk model was subsequently developed (Figure 1) and validated (Figure 2) using the discovery and validation cohorts, respectively: low risk (0 points; N=205; median survival 226 months), intermediate-1 risk (1 point; N=253; 131 months), intermediate-2 risk (2-3 points; N=457; 62 months), and high risk (4-7 points; N=153; 31 months); the corresponding median survival estimates in the validation cohort were “not reached”, 205 months, 96 months, and 44 months (inter-risk category p values <0.01 in all instances). Ten-year predictive accuracy was comparable between DIPSS-R (AUC 0.78) and DIPSS (AUC 0.78), despite the exclusion of age and constitutional symptoms, as risk variables, from the revised model. Furthermore, predictive performance was superior for DIPSS-R vs. DIPSS when analysis was stratified by age: >65 years (AUC 0.77 vs. 0.74) and ≤65 years (AUC 0.71 vs. 0.66). MVA that included high (ASXl1, SRSF2, U2AF1) and low (CALR type 1/like) risk mutations, karyotype, and DIPSS-R variables showed independent prognostic contribution from all except thrombocytopenia (p=0.2; Figure 3). Conclusion: DIPSS-R utilizes disease-related, as opposed to host-related, predictors of survival whose prognostic contribution was independent and complementary to genetic risk factors. The model preserves global applicability and allows for a more accurate assessment of disease severity for practice and research purposes.