Aspirin seems as effective as myelosuppressive agents in the prevention of rethrombosis in essential thrombocythemia

The course of essential thrombocythemia (ET) is complicated by bleeding, major thrombosis, and microvascular complications. Because about one-half of ET patients remain asymptomatic long term, the decision to use aspirin acetylsalicylic acid, (ASA) or myelotoxic drugs has not yet been clearly established. While vasomotor symptoms are improved by small doses of ASA, higher doses (900 mg/day) induce an unacceptable rate of serious hemorrhagic complications in patients with polycythemia vera. This retrospective study evaluates the utility of therapy in preventing thrombosis in ET and the efficacy and a safety of 100 mg/day of ASA in these patients. One hundred ninety-five consecutive patients with ET diagnosed in agreement with the Polycythemia Vera Study Group (PVSG) criteria are evaluated. All vascular complication before, at, or after diagnosis were recorded and related to the treatment used: no therapy, ASA alone, myelosuppressive agents or both. All treated patients had a significant reduction of thrombotic complications without increased hemorrhagic complications, in spite of therapy adopted. In addition, a significant reduction of rethrombosis was obtained in 60 patients with a previous thrombosis. A low rate of thrombosis (5.1%) was observed during the follow-up of the 135 patients previously asymptomatic for major complications. No difference appears to exist between the use of ASA and cytotoxic drugs in preventing thrombosis and rethrombosis in ET patients. However, the possible increase of cancer and leukemia with myelosuppressive drugs is minimized in patients treated with ASA. A low dose of ASA would seem to be a safe and effective agent in ET.