Efficacy and safety of low-dose aspirin in polycythemia vera. Low-dose aspirin in polycythaemia vera: a pilot study. Gruppo Italiano Studio Policitemia (GISP).
The use of aspirin for the prevention of thrombotic complications in polycythemia vera is controversial.
                We enrolled 518 patients with polycythemia vera, no clear indication for aspirin treatment, and no contraindication to such treatment in a double-blind, placebo-controlled, randomized trial to assess the safety and efficacy of prophylaxis with low-dose aspirin (100 mg daily). The two primary end points were the cumulative rate of nonfatal myocardial infarction, nonfatal stroke, or death from cardiovascular causes and the cumulative rate of nonfatal myocardial infarction, nonfatal stroke, pulmonary embolism, major venous thrombosis, or death from cardiovascular causes. The mean duration of follow-up was about three years.
                Treatment with aspirin, as compared with placebo, reduced the risk of the combined end point of nonfatal myocardial infarction, nonfatal stroke, or death from cardiovascular causes (relative risk, 0.41; 95 percent confidence interval, 0.15 to 1.15; P=0.09) and the risk of the combined end point of nonfatal myocardial infarction, nonfatal stroke, pulmonary embolism, major venous thrombosis, or death from cardiovascular causes (relative risk, 0.40; 95 percent confidence interval, 0.18 to 0.91; P=0.03). Overall mortality and cardiovascular mortality were not reduced significantly. The incidence of major bleeding episodes was not significantly increased in the aspirin group (relative risk, 1.62; 95 percent confidence interval, 0.27 to 9.71).
                Low-dose aspirin can safely prevent thrombotic complications in patients with polycythemia vera who have no contraindications to such treatment.
                Copyright 2004 Massachusetts Medical Society In this pilot study, aimed at exploring the feasibility of a large-scale trial of low-dose aspirin in polycythaemia vera (PV), 112 PV patients (42 females, 70 males. aged 17-80 years) were selected for not having a clear indication for, or contraindication to, aspirin treatment and randomized to receive oral aspirin (40 mg/d) or placebo. Follow-up duration was 16 +/- 6 months. Measurements of thromboxane A2 production during whole blood clotting demonstrated complete inhibition of platelet cyclooxygenase activity in patients receiving aspirin. Aspirin administration was not associated with any bleeding complication. Within the limitations of the small sample size, this study indicates that a biochemically effective regimen of antiplatelet therapy is well tolerated in patients with polycythaemia vera and that a large-scale placebo-controlled trial is feasible.
For patients with polycythaemia vera who have no clear indication or contraindication to aspirin therapy, available evidence suggests that the use of low-dose aspirin, when compared with no treatment, is associated with a statistically non-significant reduction in the risk of fatal thrombotic events and all-cause mortality, without an increased risk of major bleeding.