Cytoreduction Plus Low-Dose Aspirin Versus Cytoreduction in Monotherapy As Primary Prophylaxis of Thrombosis in Patients with Essential Thrombocythemia.

Abstract 2828

Antiplatelet therapy with low-dose aspirin is commonly used in combination with cytoredution for the prevention of thrombosis in patients with high-risk essential thrombocythemia (ET), as determined by age > 60 years and/or previous history of thrombosis. However, it is uncertain whether low-dose aspirin adds any benefit to cytoreductive therapy in patients without a history of thrombosis. In this study, the probability of thrombosis and bleeding was retrospectively analyzed in 248 patients with ET (median age: 66 years; 83 males, 165 females) treated with cytoreduction plus low-dose aspirin (n=170) or with cytoreduction only (n=78). Patients with a history of thrombosis or bleeding, as well as those receiving anticoagulant therapy, were excluded from the study. The indication of cytoreduction was age > 60 years (n=198), extreme thrombocytosis (n=37), microvascular disturbances (n=6), and others (n=7) First-line cytoreductive therapy consisted of hydroxyurea (n=216), anagrelide (n=27), interferon-α (n=4), and busulfan (n=1). During a median follow-up of 7.4 years (range: 0.1–26), a total of 28 thromboses (arterial, n=22; venous, n=6) were registered. At 5 years, the probability of thrombosis in patients receiving cytoreduction plus low-dose aspirin or cytoreduction only was 8% and 17%, respectively (p=0.006). No significant differences were observed depending on gender, presence of cardiovascular risk factors, JAK2 V617F mutational status, WBC count at diagnosis or type of cytoreductive therapy. At multivariate analysis, patients not receiving antiplatelet therapy were found to have a higher risk of thrombosis (HR: 3.3, 95%CI: 1.3–7.9, p=0.009). During the study period, a total of 13 major hemorrhagic events were registered (digestive, n=7, intracranial, n=3, others, n=3). At 5 years, the probability of major bleeding in patients receiving cytoreduction plus low-dose aspirin or cytoreduction as monotherapy was 6% and 4%, respectively (p=0.1). In conclusion, in patients with ET receiving cytoreductive therapy as primary prophylaxis of thrombosis, the addition of low-dose aspirin reduces the risk of thrombosis without increasing the risk of bleeding.