PB0742 - JAK2 V617F allele burden and thrombotic events in patients with JAK2 V617F positive polycythemia vera or essential thrombocythemia at high risk of thrombosis

Background: The goal of therapy of polycythemia vera (PV) and essential thrombocythemia (ET) is primarily to prevent vascular events that are the leading cause of morbidity and mortality. Patients older than 60 years or with a previous history of thrombotic complications are considered at high risk of thrombosis.

Aims: This study aimed to explore the clinical outcomes in high-risk patients with JAK2 V617F positive PV or ET.

Methods: The patients older than 60 years of age or had a history of thrombosis at diagnosis among patients with JAK2 V617F positive PV or ET from Daegu Catholic University Hospital between 2010 and 2021 were included in this retrospective study.

Results: A total of 113 patents, median age 73 years, with JAK2 V617F positive PV (n=50) or ET (n=62) were included. One hundred two patients were over 60 years old and 46 patients had a history of thrombosis or thrombotic event at diagnosis. At a median follow-up of 62.0 months, thrombosis occurred in 26.0% of PV and 25.8% of ET patients. The cumulative incidence of thrombosis at 7 years was 35.5%. Arterial thrombosis (93.8%) predominated. Median overall survival was 103.6 months (95% CI 68.8-138.4). Median thrombosis-free survival was 86 months (95% CI 68.4-103.6). Age, sex, diagnosis, and presence of vascular risk factors were not associated with thrombosis-free survival, whereas a higher JAK2 V617F allele burden (≥25%) was associated with poor thrombosis-free survival. Estimated rates of thrombosis-free survival at 7 years were 93.8% in the patients with lower JAK2 V617F allele burden ( < 25%) and 63.0% in the patients with higher JAK2 V617F allele burden (≥25%).

Conclusion(s): Current therapy remains suboptimal, with ongoing risk for thrombosis and death in high-risk PV and ET patients with higher JAK2 V617F allele burden. A novel approach will be needed in this group.