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Haematologica. 2016 Aug;101(8):926-31. doi: 10.3324/haematol.2016.146654. Epub 2016 May 12.

Antiplatelet therapy versus observation in low-risk essential thrombocythemia with a CALR mutation.

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  • 1Hematology Department, Hospital del Mar, IMIM, UAB, Barcelona, Spain
  • 2Hematotherapy and Hemostasis Department, Hospital Clínic, Barcelona, Spain.
  • 3Center for Research and Innovation of MPN (CRIMM); AOU Careggi, and Department of Experimental and Clinical Medicine, University of Florence, Italy.
  • 4Hematology Department, Hospital Clínico, Valencia, Spain.
  • 5Hematology and Medical Oncology Department, Hospital Morales Messeguer, IMIB-Arrixaca, UCAM, Murcia, Spain.
  • 6Haematology Department, Guys' and St Thomas' NHS Foundation Trust, London, UK.
  • 7Hematology, Oncology & Palliative Care, Johannes Wesling Academic Medical Center, University of Hannover Teaching Hospital, Germany.
  • 8Hematology Department, Hospital La Paz, Madrid, Spain.
  • 9Hematology Section, Uddevalla Hospital, NU Hospital Group, Sweden.
  • 10Hematology Department, Hospital Príncipe de Asturias, Alcalá de Henares, Spain.
  • 11Institute of Hematology & Blood Transfusion, Prague, Czech Republic.
  • 12Hematology Department, Hospital Ramón y Cajal, Madrid, Spain.
  • 13Hematology Department, Hospital Universitario 12 de Octubre, Madrid, Spain.
  • 14Hematology Department, Hospital Vall d'Hebron, Barcelona, Spain.
  • 15Hematology Department, Hospital Dr. Negrín, Las Palmas de Gran Canaria, Spain.
  • 16Division of Hematology, University Hospital Basel, Switzerland.
  • 17Department of Hematology, VU University Medical Center, Amsterdam, The Netherlands.
  • 18Centre for Cancer Research and Cell Biology, Queen's University, Belfast, UK.
  • 19Department of Clinical Science and Education, Karolinska Institute, South Hospital, Stockholm, Sweden.
  • 20Hematology Department, Hospital Clínic, IDIBAPS, Barcelona, Spain.
  • 21Hematology Department, Hospital del Mar, IMIM, UAB, Barcelona, Spain.


The role of antiplatelet therapy as primary prophylaxis of thrombosis in low-risk essential thrombocythemia has not been studied in randomized clinical trials. We assessed the benefit/risk of low-dose aspirin in 433 patients with low-risk essential thrombocythemia (271 with a CALR mutation, 162 with a JAK2(V617F) mutation) who were on antiplatelet therapy or observation only. After a follow up of 2215 person-years free from cytoreduction, 25 thrombotic and 17 bleeding episodes were recorded. In CALR-mutated patients, antiplatelet therapy did not affect the risk of thrombosis but was associated with a higher incidence of bleeding (12.9 versus 1.8 episodes per 1000 patient-years, P=0.03). In JAK2(V617F)-mutated patients, low-dose aspirin was associated with a reduced incidence of venous thrombosis with no effect on the risk of bleeding. Coexistence of JAK2(V617F)-mutation and cardiovascular risk factors increased the risk of thrombosis, even after adjusting for treatment with low-dose aspirin (incidence rate ratio: 9.8; 95% confidence interval: 2.3-42.3; P=0.02). Time free from cytoreduction was significantly shorter in CALR-mutated patients with essential thrombocythemia than in JAK2(V617F)-mutated ones (median time 5 years and 9.8 years, respectively; P=0.0002) and cytoreduction was usually necessary to control extreme thrombocytosis. In conclusion, in patients with low-risk, CALR-mutated essential thrombocythemia, low-dose aspirin does not reduce the risk of thrombosis and may increase the risk of bleeding.

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