Aspirin seems as effective as myelosuppressive agents in the prevention ofrethrombosis in essential thrombocythemia

The course of essential thrombocythemia (ET) is complicated by bleeding, ma jor thrombosis, and microvascular complications. Because about one-half of ET patients remain asymptomatic long term, the decision to use aspirin acet ylsalicylic acid, (ASA) or myelotoxic drugs has not yet been clearly establ ished. While vasomotor symptoms are improved by small doses of ASA, higher doses (900 mg/day) induce an unacceptable rate of serious hemorrhagic compl ications in patients with polycythemia vera. This retrospective study evalu ates 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-fi ve consecutive patients with ET diagnosed in agreement with the Polycythemi a 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 p atients had a significant reduction of thrombotic complications without inc reased 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 t he follow-up of the 135 patients previously asymptomatic for major complica tions. No difference appears to exist between the use of ASA and cytotoxic drugs in preventing thrombosis and rethrombosis in ET patients. However, th e possible increase of cancer and leukemia with myelosuppressive drugs is m inimized in patients treated with ASA. A low dose of ASA would seem to be a safe and effective agent in ET.