S199: a national retrospective cohort study of mpn-svt: results from the uk myeloproliferative neoplasms associated splanchnic vein thrombosis (mascot) registry

Background: Patients with myeloproliferative neoplasms (MPN) are at increased risk of splanchnic vein thrombosis (SVT), defined as abdominal thrombosis in portal, splenic, mesenteric or hepatic veins. MPN-SVT carries a significant mortality and morbidity burden and poses clinical management challenges. Detailed studies of this patient population are lacking. Aims: To establish a national web-based clinical registry for MPN-SVT (MASCOT Registry) and use this to investigate demographics, clinical features, co-morbidities, outcome & UK treatment practices for MPN-SVT. Methods: The MASCOT Registry is a UK-wide retrospective cohort of patients with MPN-SVT from 9 large haematology/hepatology centres. Participating centres entered pseudo-anonymised data for patients with MPN-SVT. New and historical cases were added; demographic, radiologic, clinical and outcome data were collected. Results: 232 patients with MPN-SVT were registered on the online database between May 2019 and January 2022. 1 centre registered 92 cases (40%) and 2 centres each registered 39 cases (17%) with the remaining 62 cases (27%) from 6 centres. 57% of patients were female and 43% male and the age of SVT onset was 49 years or less in 70% of patients. Median follow up was 7.3 years (range 35 days-31.8 years). SVT was diagnosed in 2009 or later in 72%. MPN was diagnosed first in 30% of patients, SVT first in 42% of patients and simultaneous diagnosis in 28%. Figure 1 shows the subtypes of MPN associated with SVT. Multiple splanchnic vein thromboses were observed in 42% of patients. Of those with single vein thrombosis, the portal vein was affected in 26% and the hepatic vein in 23%. Initial anticoagulation treatment was in line with local policy. TIPSS (transjugular intrahepatic portosystemic shunt) was performed in 21% and thrombolysis in 7%. Warfarin only was the preferred long-term anticoagulant (53%). Cytoreduction at registration comprised 44% of patients on hydroxycarbamide, 18% on Pegylated interferon, 16% on ruxolitinib and 8% on no therapy. 37 patients required major abdominal surgery and 17 received liver transplants. 71 patients (33%) suffered from other non-SVT thromboses (34% pre-SVT, 9% simultaneously and 57% post-SVT), comprising 84 thrombotic events (60 venous, 24 arterial). Grade 3+ haemorrhage was observed in 60 patients (28%), of which the majority (48%) occurred within the first year of SVT diagnosis. 111 patients (51%) were re-imaged at least once within 12 months post-SVT, demonstrating clot extension in 12%, recanalization in 25% and stable appearances in 54%. Overall survival was 88% with 14 deaths, of which 6 were disease-related. Median age at death was 72 years and death occurred at a median of 12 years post SVT diagnosis. Image:Summary/Conclusion: This is one of the largest cohort studies of patients with MPN-SVT to date with over 70% diagnosed in the last 13 years. Similar to previous published studies, our evidence corroborates the female predominance and relatively young age at diagnosis. Our data highlight the significant morbidity and mortality burden incurred by patients with MPN-SVT, including a substantially lower rate of re-canalisation compared to a recent meta-analysis of all patients with SVT and high rates of thrombosis recurrence. We have highlighted variations in clinical practice including choice of anticoagulant, preferred cytoreductive agent and use of thrombolysis and TIPSS. Future studies to further understand this patient population should be focused on access to optimal care, the aetiology of thrombosis, optimum anticoagulation management and strategies to minimise bleeding.