Efficacy and Safety of Low-Dose Aspirin in Polycythemia Vera

Background The use of aspirin for the prevention of thrombotic complications in polycythemia vera is controversial. Methods We enrolled 518 patients with polycythemia vera, no clear indication for aspirin treat- ment, 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 myo- cardial infarction, nonfatal stroke, or death from cardiovascular causes and the cumu- lative 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. Results Treatment with aspirin, as compared with placebo, reduced the risk of the combined end point of nonfatal myocardial infarction, nonfatal stroke, or death from cardiovascu- lar 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 mor- tality and cardiovascular mortality were not reduced significantly. The incidence of ma- jor bleeding episodes was not significantly increased in the aspirin group (relative risk, 1.62; 95 percent confidence interval, 0.27 to 9.71). Conclusions Low-dose aspirin can safely prevent thrombotic complications in patients with poly- cythemia vera who have no contraindications to such treatment.