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Low-Dose Aspirin in Polycythemia Vera

Among patients who didn't have histories of thrombosis, aspirin therapy reduced thrombotic events during 3 years, without increasing major bleeding events.

Thrombotic complications occur frequently in patients with polycythemia vera; however, the safety of prophylactic aspirin is controversial. In a multicenter, randomized, double-blind European study, 518 patients with polycythemia vera received either enteric coated aspirin (100 mg daily) or placebo. Most patients had undergone phlebotomy, cytoreductive drug therapy, or both; about 90% had no previous history of arterial or venous thrombosis. At baseline, mean hematocrit was 48%, and mean platelet count was 382,000/mm³.

During an average follow-up of 3 years, a primary combined endpoint (myocardial infarction, stroke, pulmonary embolism, major venous thrombosis, or cardiovascular death) occurred significantly less often in the aspirin group than in the placebo group (3% vs. 8%, P=0.03). Many secondary thrombotic endpoints also occurred less frequently with aspirin, but most differences did not reach significance due to small numbers of events. A trend emerged toward more minor bleeding episodes with aspirin than with placebo, but no difference was noted in major bleeding (3 and 2 episodes).

Comment: These findings provide reassurance that low-dose aspirin can safely reduce the incidence of thrombotic events in patients with polycythemia vera who have no history of thrombosis. An editorialist notes that many patients in this trial had undergone inadequate phlebotomy (more than half had hematocrits higher than 45%); he speculates that the benefit of aspirin might have been negligible if patients had received more aggressive phlebotomy.

— Allan S. Brett, MD

Published in Journal Watch General Medicine February 6, 2004

Citation(s):

Landolfi R et al. Efficacy and safety of low-dose aspirin in polycythemia vera. N Engl J Med 2004 Jan 8; 350:114-24.

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Spivak J. Daily aspirin -- Only half the answer. N Engl J Med 2004 Jan 8; 350:99-101.

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