Li, Chi‐Yuan

7029 Background: A leukocyte count of > 15 ×109/L has recently been associated with myocardial infarction in polycythemia vera (PV). In the current study, we examine the impact of such degree of leukocytosis on survival, leukemic transformation (LT), and thrombosis in a large cohort of PV patients from a single institution Methods: Data was abstracted from the medical records of a consecutive cohort of patients with PV defined by the World Health Organization criteria. Results: i. Patient characteristics The study cohort included 459 patients (median age, 60 years). Median follow-up was 64 months. ii. Survival In a multivariable analysis, advanced age, leukocyte count of = 15 × 109/L, and arterial thrombosis at diagnosis were significantly associated with inferior survival. A prognostic model based on age = 60 years and leukocyte count = 15 × 109/L separated low-risk, intermediate-risk, and high-risk patient groups with respective median survivals of 272, 162, and 108 months (p<0.0001). iii. Leukemic transformation In a multivariable analysis, only leukocyte count was significantly associated with LT; median leukemia-free survival for patients with leukocyte count = 15 × 109/L was 273 months vs. not reached for those with lower leukocyte count (p<0.0001). iv. Thrombosis at diagnosis In multivariable analysis, arterial thrombosis at diagnosis was significantly associated with previous history of arterial thrombosis, hypertension, and tobacco use; venous thrombosis at diagnosis was significantly associated with previous venous event and splenomegaly. v. Thrombosis during follow- up In multivariable analysis, arterial thrombosis during follow-up was significantly associated with previous arterial event, hypertension, and tobacco use; venous thrombosis during follow-up was significantly associated with previous venous event, diabetes mellitus, advanced age, and leukocyte count = 1,500 × 109/L. Conclusions: The current study for the first time identifies leukocytosis as a risk factor for inferior survival, LT risk, and venous thrombosis in PV. No significant financial relationships to disclose.