Treatment Choices in Essential Thrombocythemia

Essential thrombocythemia (ET) is one of a group of blood disorders called myeloproliferative neoplasms. Other types of myeloproliferative neoplasms include primary myelofibrosis and polycythemia vera.

Genetic mutations in essential thrombocythemia lead to extremely high platelet counts (thrombocytosis). Many people are without symptoms at the time of diagnosis and will have a normal life expectancy. Complications include:

• Clot formation, which can lead to stroke, heart attack, deep vein thrombosis, or pulmonary embolism (a clot in a lung)
• Myelofibrosis
• Acute myeloid leukemia (AML)
• Acquired von Willebrand disease, a bleeding disorder

The majority of people will require therapy at some point to prevent complications. However, life expectancy is similar to or slightly less than the healthy general population.

Treatment Options

If you are diagnosed with essential thrombocythemia the natural next question is, “what are my treatment options?” There are several options that your healthcare provider should discuss with you. The treatment your healthcare provider recommends is likely based on several factors: your symptoms, your age, and your laboratory values. Most people will go several years without requiring treatment, which is typically started if you develop a clot.

1. Aspirin: Daily low-dose aspirin is typically used to treat people with vasomotor symptoms. Vasomotor symptoms include headaches, dizziness, chest pain, burning of the hands and feet, and visual changes. It is not uncommon for aspirin therapy to be used with other treatments. High dose aspirin therapy has been associated with an increased bleeding risk and is not recommended.
2. Hydroxyurea: The oral chemotherapy agent hydroxyurea reduces the risk of thrombosis in essential thrombocythemia by reducing the platelet count. Hydroxyurea is started at a low dose and escalated until the platelet count is near normal (100,000–400,000 cells per microliter). Hydroxyurea is generally well tolerated without significant side effects. Side effects include hyperpigmentation (darkening) of the skin, nail changes (usually dark lines under the nail), and skin rash. Hydroxyurea also lowers the white blood cell count (particularly the neutrophil count) and the hemoglobin which requires close monitoring with complete blood counts (CBC).
3. Anagrelide: Anagrelide is an oral medication that lowers the platelet count by inhibiting the production of platelets in the bone marrow. It is typically used when hydroxyurea is not effective. Similar to hydroxyurea, anagrelide is started at a low dose and increased until the desired effect. Side effects include headaches, palpitations (rapid heart rate), fluid retention, and diarrhea. These side effects typically resolve with continued treatment.
4. Alpha interferon: Alpha interferon can be used to control the platelet count in essential thrombocythemia, polycythemia vera, and primary myelofibrosis. It can also reduce the size of the spleen. Alpha interferon is administered subcutaneously (under the skin) daily. Alpha interferon is also available in a long-acting form called pegylated interferon that can be given once per week. Interferon therapy is typically reserved for pregnant women or people who do not respond to hydroxyurea therapy.
5. Plateletpheresis: Plateletpheresis is a procedure that removes the platelets from the circulation. Blood is removed via an intravenous (IV) catheter and collected in a machine where the platelets are separated from the other parts of the blood (white blood cells, red blood cells, and plasma). The blood, minus the platelets, is returned to the body via IV either with saline solution or plasma. Plateletpheresis is reserved for people with extremely high platelet counts, serious clot formation (in lungs, brain), or bleeding. The effect of plateletpheresis is temporary so another treatment will need to be started for long-term control of the platelet count.

All of the treatments discussed above do not cure essential thrombocythemia. They only decrease the platelet count thereby decreasing the risk of developing a clot or acquired von Willebrand disease. At this time, there is no curative therapy for essential thrombocythemia. Fortunately, despite the lack of curative therapy, the majority of people with essential thrombocythemia can live full productive lives.