Primary myelofibrosis (PM) is a myeloproliferative neoplasm characterised by bone marrow fibrosis and extramedullary hematopoiesis. Both clinical findings and laboratory parameters are used for prognostic scores in Myelofibrosis patients. In addition, the degree of bone marrow fibrosis has an important prognostic value and has correlation with overall survival. Recently, bone marrow fibrosis was correlated with degree of splenic stiffness (SS) measured by imaging elastography techniques. Despite these findings, there were patients with insignificant measures that could not be classified according to marrow fibrosis. In order to advance knowledge in this field, we studied splenic and hepatic stiffness (HS) in patients with myelofibrosis using elastography by two methods, ultrasonography (EUS) and magnetic resonance elastography (MRE), and its correlation with prognostic scores and bone marrow fibrosis.

This is a prospective, cross-sectional, observational study in patients from the outpatientclinic for myeloproliferative neoplasms who had given informed consent according to procedures approved by institutions ethical committee. Patients with PM, as well as post-essential thrombocythemia or post-polycythemia vera myelofibrosis, were included in this study. Myelofibrosis patients with diagnosis of other associated pathologies that may alter SS, as portal hypertension or cirrhosis, were excluded from the study. Patients were assessed for splenic stiffness measured by ultrasound conducted by two examiners, with more than 10 years of experience. EUS was performed in US Epiq 7 equipment - Philips – with ARFI elastometry methodology. The SS measurements was reported in m/s. In addition, they were also evaluated for splenic and liver stiffness by MRI technique. All exams were performed in 1.5 T MR equipment (Magneton Aera, Siemens Healthineers, Erlangen, Germany) and the MRI protocol included T2-weighted and gradient-echo MRE sequences using steady-state 60-Hzexcitation and an external driver placed on the right side and, on the left side of theabdomen. The measures of SS were also obtained by two experienced examiners.

At this moment we present the results of 16 patients with myelofibrosis (PM: 8 cases; post-PV myelofibrosis: 2 cases; post-ET myelofibrosis: 6 cases). The median age was 69y (41-88y) and 62,5% of participants were male. The JAK2 V617F mutation was detected in 9 cases; three cases were CALR positive, and three cases were triple negative. The CBC showed: Hb: 10.9 g/dL (6.5-18.7); WBC (x10/L): 9.17 (1.8-44.5) and platelets (x10/L): 393 (10-957). Our preliminary results show that bone marrow fibrosis increased according to splenic stiffness by EUS and MRE. Patients with osteosclerosis also presented a higher SS by MRE. We could not find correlation of splenic stiffness with prognostic score DIPSS plus, although Int-2/High risk patients presented a trend to be associated with higher liver stiffness.

To the moment, our preliminary findings suggest a correlation between SS and degree of bone marrow fibrosis and osteosclerosis, though the correlation between both measures and prognostic scores is still to be determined. We expect to have a better definition forall correlations, as we progress through the assessment of the other patients in our service.