PO110 | CLINICAL OUTCOMES AND SURVIVAL OF UNUSUAL SITE VENOUS THROMBOSIS IN PATIENTS WITH AND WITHOUT MYELOPROLIFERATIVE NEOPLASMS: A RETROSPECTIVE SINGLE-CENTER STUDY

I. Bertozzi, M.T. Sartori, G. Libralon, M. Zerbinati, A. Galbiati, P. Simioni | Department of Medicine, University of Padova, Italy

Background and Aims. Unusual site venous thromboses (USVT) are rare conditions involving the cerebral (CVT), splanchnic (SVT), renal, retinal, and gonadal veins. Available evidence regarding specific risk factors, prognosis, recurrence risk and survival is poorer than that for classical manifestations of venous thromboembolism (VTE). Myeloproliferative neoplasms (MPNs) are clonal disorders characterized by growth factor-independent proliferation of hematopoietic stem cells and bone marrow hypercellularity. MPNs are established prothrombotic conditions predisposing to USVT, particularly SVT, and are associated with an increased risk of bleeding complications and thrombotic recurrences. Here we analyze characteristics and long-term outcomes of a large single center cohort of CVT and SVT, associated or not with MPN.
Methods. We conducted a single-center retrospective study including 33 patients with CVT (12 MPN and 21 non-MPN) and 68 patients with SVT (49 MPN and 19 non-MPN) diagnosed and followed at our Department in the last five decades (36 M, 65 F, median age at USVT 42 y, median follow-up 143 m). Patients with malignancies other than MPN or liver cirrhosis at the time of USVT were excluded. Demographic characteristics, VTE risk factors, antithrombotic therapy, thrombosis recurrences in typical or atypical sites, major bleedings, and all-cause mortality were recorded. MPN diagnosis was performed according to current criteria at first observation and, when available, revised to the most recent ICC criteria. Survival analysis was performed with Cox regression model.
Results. Among the 33 CVT patients (12 M, 21 F) 36,4% (n=12) were MPN related, while SVT (24 M, 44 F) was associated with MPN in 72% (n=49) of cases. No gender or median age at USVT differences were observed comparing MPN to non-MPN patients. At least one VTE risk factor was present in 75% of non-MPN patients compared with 39.3% of MPN patients. Cumulative incidence of thrombotic recurrence was similar in the two groups, namely 2.43/100 patients/year in non-MPN (95% CI 1.1-4.2) and 2.96/100 patients/year (95% CI 1.8-4.3) in MPN patients. However, within the CVT subgroup, thrombotic recurrences were more frequent in MPN patients (n = 6) than in non-MPN patients (n=2, p=0.015). Cumulative incidence of major bleeding after USVT was significantly higher in patients with MPN (3.28/100 patients/year, 95% CI 1.94-4.62) compared with those without MPN (0.76/100 patients/year, 95% CI 0.15-1.8). In age-and-sex-adjusted Cox regression analysis, MPN was confirmed as an independent risk factor for major bleeding (HR 5.1, 95% CI 1.5–17.3; p=0.01; Figure 1) in USVT patients. All-cause mortality did not differ between MPN and non-MPN patients.
Conclusions. Among our patients with USVT, MPN patients showed an approximately fivefold higher risk of major bleeding than non-MPN patients, along with a higher rate of thrombotic recurrences in the CVT subgroup. Despite a lower prevalence of additional transient or acquired VTE risk factors, USVT-MPN patients experienced comparable overall recurrence rates, supporting the role of the underlying clonal disorder as a persistent prothrombotic driver. Altogether, our data emphasize the need for prospective studies to better define optimal management strategies and to refine risk-adapted therapeutic approaches in patients with MPN-associated USVT that take into account the delicate balance between thrombotic and hemorrhagic risk in these patients.