Essential thrombocythemia (ET) is a type of blood cancer known as a myeloproliferative neoplasm. It involves the abnormal development and function of bone marrow cells that produce blood cells, and leads to the overproduction of blood cells known as platelets. Red blood cells and white blood cells may also be overproduced. There is currently no cure for ET, but the condition can often be well managed for long periods of time. In rare cases, ET may progress to myelofibrosis (scarring of the bone marrow) or acute myeloid leukemia (AML).
The following is a general overview of the diagnosis and treatment of ET. Each person with ET is different, and the specific characteristics of your condition will determine how it is managed. The information on this Web site is intended to help educate you about treatment options and to facilitate a shared decision-making process with your treating physician.
Many people with ET do not have symptoms from the disease. Those who do have symptoms may experience the following1:
Overproduction of blood cells and changes to blood flow increase the risk of serious blood clots in people with ET. This can lead to life-threatening conditions such as heart attack, stroke, or pulmonary embolism. ET can also lead to abnormal bleeding and to pregnancy complications. Women who are pregnant or considering becoming pregnant may wish to talk with their doctor about how to manage their health.
Blood tests and (in many cases) bone marrow examination provide the information necessary to diagnosis ET.2 ET involves a high platelet count. Platelets are blood cells that play an important role in blood clotting. In addition, roughly half of people with ET will test positive for a mutation in the Janus kinase 2 (JAK2) gene; the exact role of this gene continues to be studied. Bone marrow examination typically reveals an increase in megakaryocytes (platelet-forming cells) that have a certain, characteristic appearance.
The need for treatment and choice of treatment depends in part on a patient’s risk of blood clots.2 Patients who are older or who have history of blood clots are considered high-risk and may require more extensive treatment than patients who are low-risk. Management of low-risk patients may involve close observation or low-dose aspirin. Patients who have a high risk of abnormal bleeding may need to avoid aspirin.
Low-dose aspirin: Reduces the risk of blood clots.
Hydroxyurea: May be used for the treatment of high-risk patients. Hydroxyurea suppresses blood cell production in the bone marrow.
Other drugs that may be used include interferon alfa, anagrelide, and busulfan. Once again, the goal is to manage blood cell concentrations and to reduce the risk of serious blood clots.
In rare cases, ET progresses to myelofibrosis (scarring of the bone marrow) or acute myeloid leukemia (AML). Among people with ET, the 10-year risk of myelofibrosis is roughly 1% and the 10-year risk of AML is less than 1%.2 For information about the management of these conditions, click on one of the following:
The development of more effective cancer treatments requires that new and innovative therapies be evaluated with cancer patients. Clinical trials are studies that evaluate the effectiveness of new drugs or treatment strategies. Future progress in the treatment of essential thrombocythemia will result from the continued evaluation of new treatments in clinical trials. Participation in a clinical trial may offer patients access to better treatments and advance the existing knowledge about treatment of this cancer. Patients who are interested in participating in a clinical trial should discuss the risks and benefits of clinical trials with their physician. Areas of active investigation aimed at improving the treatment of essential thrombocythemia include the following:
JAK inhibitors: Targeted drugs known as JAK inhibitors may change the way in which myeloproliferative neoplasms are treated. These drugs target abnormal cell signaling that is through to contribute to the growth of myeloproliferative neoplasms. A JAK inhibitor has been approved for the treatment of myelofibrosis, and JAK inhibitors are also being evaluated for the treatment of ET and polycythemia vera.
HDAC inhibitors: Other targeted drugs that are being evaluated for ET include histone deacetylase (HDAC) inhibitors. These drugs—which include givinostat, vorinistat, panobinostat, and others—interfere with enzymes that may contribute to cancer growth.
1 National Cancer Institute: PDQ® Chronic Myeloproliferative Disorders Treatment. Bethesda, MD: National Cancer Institute. Date last modified 08/07/2013. Available at: http://cancer.gov/cancertopics/pdq/treatment/myeloproliferative/Patient. Accessed 10/11/2013.
2 Tefferi A. Polycythemia vera and essential thrombocythemia: 2013 update on diagnosis, risk-stratification, and management. American Journal of Hematology. 2013;88:508-516.