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Essential Thrombocythemia



In a case-controlled observational study of 65 low-risk patients (<60 years of age, platelet count <1,500 × 109 /L, and no history of thrombosis or hemorrhage) with a median follow-up of 4.1 years, the thrombotic risk of 1.91 cases per 100 patient years and hemorrhagic risk of 1.12 cases per 100 patient years was not increased over the normal controls.[9] A prospective randomized trial of 809 patients compared hydroxyurea plus aspirin versus anagrelide plus aspirin.[10] Although the platelet-lowering effect was equivalent, the anagrelide group had significantly more thrombotic and hemorrhagic events (hazard ratio [HR] = 1.57; P = .03) and more myelofibrosis (HR = 2.92; P = .01). No differences were seen for myelodysplasia or acute leukemia.[11][Level of evidence: 1iiA] Many clinicians use hydroxyurea or platelet apheresis prior to elective surgery to reduce the platelet count and to prevent postoperative thromboembolism. No prospective or randomized trials document the value of this approach.

Among low-risk patients (defined as age 60 years or younger with no prior thrombotic episodes), a retrospective review of 300 patients showed benefit for antiplatelet agents in reducing venous thrombosis in JAK2-positive cases and in reducing arterial thrombosis in patients with cardiovascular risk factors.[12] Balancing the risks and benefits of aspirin for low-risk patients can be difficult.[13]

Treatment options:

  1. No treatment, unless complications develop, if patients are asymptomatic, younger than 60 years, and have a platelet count of less than 1,500 × 109 /L.
  2. Hydroxyurea.[6]
  3. Interferon-alpha [14,15] or pegylated interferon-alpha.[16]
  4. Anagrelide.[11,17]

Current Clinical Trials

Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with essential thrombocythemia. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.

General information about clinical trials is also available from the NCI Web site.


  1. Tefferi A, Thiele J, Vardiman JW: The 2008 World Health Organization classification system for myeloproliferative neoplasms: order out of chaos. Cancer 115 (17): 3842-7, 2009.
  2. Passamonti F, Thiele J, Girodon F, et al.: A prognostic model to predict survival in 867 World Health Organization-defined essential thrombocythemia at diagnosis: a study by the International Working Group on Myelofibrosis Research and Treatment. Blood 120 (6): 1197-201, 2012.
  3. Barbui T, Thiele J, Carobbio A, et al.: Disease characteristics and clinical outcome in young adults with essential thrombocythemia versus early/prefibrotic primary myelofibrosis. Blood 120 (3): 569-71, 2012.
  4. Campbell PJ, Green AR: The myeloproliferative disorders. N Engl J Med 355 (23): 2452-66, 2006.
  5. Harrison CN, Bareford D, Butt N, et al.: Guideline for investigation and management of adults and children presenting with a thrombocytosis. Br J Haematol 149 (3): 352-75, 2010.
  6. Cortelazzo S, Finazzi G, Ruggeri M, et al.: Hydroxyurea for patients with essential thrombocythemia and a high risk of thrombosis. N Engl J Med 332 (17): 1132-6, 1995.
  7. Harrison C, Kiladjian JJ, Al-Ali HK, et al.: JAK inhibition with ruxolitinib versus best available therapy for myelofibrosis. N Engl J Med 366 (9): 787-98, 2012.
  8. Barosi G, Besses C, Birgegard G, et al.: A unified definition of clinical resistance/intolerance to hydroxyurea in essential thrombocythemia: results of a consensus process by an international working group. Leukemia 21 (2): 277-80, 2007.
  9. Ruggeri M, Finazzi G, Tosetto A, et al.: No treatment for low-risk thrombocythaemia: results from a prospective study. Br J Haematol 103 (3): 772-7, 1998.
  10. Harrison CN, Campbell PJ, Buck G, et al.: Hydroxyurea compared with anagrelide in high-risk essential thrombocythemia. N Engl J Med 353 (1): 33-45, 2005.
  11. Green A, Campbell P, Buck G: The Medical Research Council PT1 trial in essential thrombocythemia. [Abstract] Blood 104 (11): A-6, 2004.
  12. Alvarez-Larrán A, Cervantes F, Pereira A, et al.: Observation versus antiplatelet therapy as primary prophylaxis for thrombosis in low-risk essential thrombocythemia. Blood 116 (8): 1205-10; quiz 1387, 2010.
  13. Harrison C, Barbui T: Aspirin in low-risk essential thrombocythemia, not so simple after all? Leuk Res 35 (3): 286-9, 2011.
  14. Sacchi S: The role of alpha-interferon in essential thrombocythaemia, polycythaemia vera and myelofibrosis with myeloid metaplasia (MMM): a concise update. Leuk Lymphoma 19 (1-2): 13-20, 1995.
  15. Gilbert HS: Long term treatment of myeloproliferative disease with interferon-alpha-2b: feasibility and efficacy. Cancer 83 (6): 1205-13, 1998.
  16. Quintás-Cardama A, Kantarjian H, Manshouri T, et al.: Pegylated interferon alfa-2a yields high rates of hematologic and molecular response in patients with advanced essential thrombocythemia and polycythemia vera. J Clin Oncol 27 (32): 5418-24, 2009.
  17. Anagrelide, a therapy for thrombocythemic states: experience in 577 patients. Anagrelide Study Group. Am J Med 92 (1): 69-76, 1992.

WebMD Public Information from the National Cancer Institute

Last Updated: February 25, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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