Progression To Myelofibrosis In Patients With Essential Thrombocythemia

Topic: Myeloproliferative neoplasms — Clinical

Background:Essential thrombocythemia (ET) is a myeloproliferative neoplasm characterized by clonal blood cellproliferation, excessive platelet (PLT) production, constitutional symptoms, increased risk of vascularcomplications, and risk of progression to myelofibrosis (MF). Previous prognostic studies of patients with ETwere largely based on retrospective analyses and there are limited prospective data regarding ET diseaseprogression. The prospective Myelofibrosis and Essential Thrombocythemia Observational Study (MOST)collected real-world data from patients with ET.

Aims:To evaluate ET progression in patients enrolled in MOST

Methods:MOST (NCT02953704) enrolled patients with ET aged ≥60 years, or with a history of thromboembolic events(TEs) or who were receiving ET-directed therapy (except aspirin only). Data on baseline clinical characteristicswere collected as previously described (Yacoub A, et al. Clin Lymphoma Myeloma Leuk. 2021;21(7):461–9). ET-to-MF progression was defined as meeting ≥1 of the following criteria on study: 1) bone marrow biopsy withfibrosis grade ≥2 or pathological diagnosis of MF; 2) death due to MF/myelodysplastic syndrome/acutemyeloid leukemia; 3) circulating blasts >1% and new/worsening splenomegaly (SPM); 4) new/worsening SPMand ≥2 of: white blood cell (WBC) count >11×109/L, hemoglobin (Hb) <10g/dL, and PLT count <100×109/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, most of whomprogressed due to fibrosis (criterion 1, 56.6%); 15.1%, 11.3%, and 28.3% of patients progressed due to criteria2, 3, and 4, respectively. Notably, only 176 patients (14.2%) enrolled had bone marrow data available.Comparison of the enrollment characteristics of patients with vs without progression showed no differences inage at enrollment or diagnosis (Table). However, time from diagnosis to enrollment and from diagnosis to endof study were significantly longer in patients with vs without progression (median 7.9 vs 4.2 years, median 12.7vs 9.0 years, respectively; both P=0.001). Of all enrolled patients with vs without progression tested for knowndriver mutations, a higher percentage with progression were JAK2-positive vs those without (80.6% [29/36] vs69.7% [598/858]). Similar percentages of patients with vs without progression were receiving ET-directedtherapies at enrollment (94.3% vs 94.8%). Among patients with vs without progression, mean baseline Hb wassignificantly lower (12.5g/dL vs 13.1g/dL; P=0.026), mean WBC counts were significantly higher (10.4×109/L vs7.4×109/L; P<0.001), and mean PLT counts were similar (418.6×109/L vs 455.0×109/L; P=0.466). Baseline MPN-SAF TSS was similar for patients with vs without progression. A lower percentage of patients with vs withoutprogression had ≥1 TEs (1.9% [1/53] vs 3.7% [44/1184]) during the study, but a higher percentage had ≥1hemorrhagic event (7.5% [4/53] vs 1.3% [15/1184]).

Summary/Conclusion:This analysis of data from MOST showed that 4.3% of patients with ET progressed to MF during the studyperiod. Compared with patients without progression, patients with ET-to-MF progression had longer diseaseduration, higher WBC count, and lower Hb at enrollment; symptom burden at enrollment was similar between

https://clin.larvol.com/abstract-detail/EHA 2024/70979962