The risk of venous and arterial thrombosis in polycythemia vera patients with secondary malignancies.

e18599 Background: Polycythemia vera (PCV) is a myeloproliferative neoplasm defined by the clonal proliferation of hematopoietic progenitor cells. PCV is associated with an increased risk of thrombosis, which is stratified according to patient age and thrombosis history. Secondary malignancies (SM) develop in 8.4% of PCV patients. While cancer-associated thrombosis is an evolving field, the risk of thrombosis among PCV patients with SM is not well described. Methods: This study is a secondary analysis of data from a previously conducted study approved by the University of Illinois College of Medicine Peoria IRB. We identified 145 JAK2-positive adult patients (2015 - 2024) with elevated hemoglobin (≥160 g/L for females, ≥165 g/L for males) and no cancer history prior to PCV diagnosis. The relative risk (RR) of venous and arterial thrombosis among patients with SM compared to those without SM was calculated. Results: The rate of SM was 238.0 per 1000 person-years, with Myelodysplastic Disease (55.8%), Myeloid Leukemia (11.5%) and Lung Cancer (9.6%) being the most common. There were no statistically significant differences in age, gender and race between patients who developed SM compared to those who did not. Patients with SM had a greater overall risk of arterial (RR: 1.11, 95% CI: 1.09 - 1.13) and venous thrombosis (RR: 1.09, 95% CI: 1.07 - 1.10), as shown in Table 1. PCV patients with SM were less likely to have pulmonary embolisms (PE) (RR: 0.79, 95% CI: 0 0.78 - 0.81). Conclusions: This study demonstrated an anticipated increased risk of thrombosis among PCV patients with SM, except for PE. However, this study did not compare thrombotic risk factors, rates of PCV treatment, or details of individual clotting events between groups. This analysis is also limited by a small sample size. Future studies should evaluate the risks and benefits of antithrombotic prophylaxis among PCV patients with SM. Providers could consider these findings when stratifying the risk of thrombosis and individualizing treatment decisions. The incidence and relative risk of thrombosis among Polycythemia Vera (PCV) patients with secondary malignancies (SM) compared to those with Polycythemia Vera only. PCV with SM (n/1000 person years) PCV only (n/1000 person years) Relative Risk 95% Confidence Interval Arterial Thrombosis 278.49 251.09 1.11 1.09, 1.13 STEMI/NSTEMI 282.87 229.27 1.23 1.22, 1.25 TIA/CVA 276.73 255.96 1.08 1.07, 1.10 Venous Thrombosis 291.99 268.63 1.09 1.07, 1.10 DVT 309.30 273.68 1.13 1.11, 1.15 PE 201.71 254.53 0.79 0.78, 0.81 Thrombosis incidence is expressed per 100,000 person-years. CI: 95% Confidence Interval; DVT: Deep Vein Thrombosis; NSTEMI: Non-ST-Elevation Myocardial Infarction; PE: Pulmonary Embolism; RR: PCV: Polycythemia Vera; Relative Risk; SM: Secondary Malignancies; STEMI: ST-Elevation Myocardial Infarction; TIA/CVA: Transient Ischemic Attack/Cerebrovascular Accident.