Normal Life Expectancy and Thrombosis-Free Survival in Aspirin Treated Essential Thrombocythemia

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Abstract
Focusing on platelet-mediated erythromelalgia as a specific, presenting, and single sign of essential thrombocy themia (ET) we were able to define the characteristic peripheral blood and bone marrow findings in ET patients. From 1974 to 1986 we treated 20 symptomatic ET patients with microvascu lar circulation disturbances including erythromelalgia (N = 18), atypical or typical transient ischemic attacks (N = 6), or acute coronary ischemic syndrome (N = 3) with aspirin and one course of busulfan. The mean platelet counts before and after busulfan treatment were 1,009 (range 545-1,525) and 241 (range 159-315) x 109/L, respectively. After induction of a complete remission, treatment with busulfan and aspirin was discontinued until symptoms returned. All 20 patients remained asymptomatic as long as ET was in maintained remission (platelet 9/L) for 4 to 61 (mean 36) months. Eight patients became symptomatic and 4 patients remained asymp tomatic at relapse of ET after a follow-up period of 19 to 61 and 31 to 46 months, respectively. Platelet counts at time of symp tomatic relapse in the 8 patients were 410, 450, 490, 500, 515, 545, 548, and 635 x 109/L and at time of asymptomatic relapse in 4 ET patients 577, 600, 648, and 725 x 109/L. Based on these observations, since 1986 we followed the strategy to treat ET patients with aspirin as long as the platelet count was between 400 and 1,000 up to 1,250 x 109/L. Clear indications to reduce the platelet count were bleeding, aspirin side effects, and plate lets counts above 1500 x 109/L. This nonleukemogenic or least toxic approach in ET is the rationale behind the normal life expectancy and subsequent thrombosis-free survival in 68 ET patients after a mean follow-up period of 6.2 years. Key Words: Essential thrombocythemia—Platelets—Erythro— melalgia—Transient ischemic attacks—Thrombosis—Life ex pectancy—Aspirin—Busulfan.