Understanding the Basics of ET and How to Treat It

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Topics include: Treatments and Understanding

During this segment from the Living Well series, Dr. Bart Scott, breaks down what’s occurring at a cellular level with an essential thrombocythemia (ET) diagnosis. Dr. Scott also discusses physical reactions patients may experience, common mutations seen in ET, and treatment options available to combat the disease.

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Beth Kart Probert:

For our viewers, could you explain a bit about ET—just help us understand really what it is and more importantly, what are we treating it with and what are the goals of treatment for ET? 

Dr. Scott:              

ET stands for central thrombocytosis or essential thrombocythemia, so it’s been called both of those names, but the principle issue is overproduction of platelets. When you see the blood counts of the patient with essential thrombocytosis, their platelet counts are elevated. There can be a wide range of how elevated we’re talking about. It could be anywhere from 650 to even greater than 2 million.

When you have a platelet count that’s really high, like above a million, paradoxically there’s an increased risk of bleeding. That’s because the platelets have, on their cell surface, what’s called a von Willebrand factor cleaning protein. It actually cleans a portion of the blood that helps in clotting. So even though they have all of these platelets, and we associate platelets with preventing bleeding and bruising—when the platelets are extremely high like that, patients can have bleeding like nose bleeding, gum bleeding. 

But the real problem with essential thrombocytosis is clotting. The number one cause of death in people with ET is due to blood clots. And so James was just saying, he presented with this basically heart attack that he probably wouldn’t have survived if he hadn’t been in the hospital already. That can be a common presentation that you see with essential thrombocytosis blood clots.

So the reason to treat patients with essential thrombocytosis when they are treated is to lower their risk for blood clots, to lower the risk for thrombosis. The standard therapy for ET would be aspirin, a baby aspirin a day, and then you look at different types of risk factors to determine whether or not they need cytoreductive therapy. Cytoreductive therapy is basically given to lower the blood counts.

The risk factors that we would look at age, would be history of prior thrombosis, also white count is another risk factor that’s come out recently that can predispose people for risk of blood clots. But there is a prediction model. It’s called an IPSET prediction model, and it’s an international prognostic model to determine the risk of thrombosis in patients with ET. You can look at that, and you can see what risk factors this patient has. 

Interestingly, JAK2 mutations, so having ET with a JAK2 mutation is another risk factor for thrombosis. But if they are high risk for thrombosis, either due to age or history of thrombosis, other risk factors like cardiovascular risk factors or due to the IPSET model, these are patients that are treated with cytoreductive therapy. There are many choices for cytoreductive therapy and two of them have already—actually, three of them have already mentioned.

That would be hydroxyurea (Hydrea), which is a common agenda that is used; another choice would be pegylated interferon or peginterferon alfa-2a (Pegasys). And then another choice would be anagrelide (Agrylin). There have been two randomized trials that I’m aware of comparing hydroxyurea to anagrelide. One showed a benefit with hydroxyurea over anagrelide. The other one was basically equivalent. But for me, my preference is Hydrea unless they are a younger patient.


And in those patients I typically prefer Pegasys. I think there’s more data that’s needed to determine whether hydroxyurea or Pegasys would be the best first choice. There is a randomized trial that either has completed accrual or will soon complete accrual where they compared hydroxyurea to pegylated interferon. It’s frontline cytoreductive therapy for people with PV and ET. That will help us to answer the question which is better between hydroxyurea or pegylated interferon. But both of those would be choices for initial cytoreductive therapy.

Recently one of the big things that we’ve learned about with all myleoproliferative neoplasms is the underlying driver mutations. All of the myeloproliferative neoplasms share in common up regulation of the JAK-STAT pathway. And the same thing of course is true with ET. 

And so there are three common mutations seen in ET: JAK2V617F would be the most common, and then calreticulin and then what’s called the MPL mutation. So you would test your patients for those mutations if you suspect a myeloproliferative neoplasm. They’re helpful not only from the standpoint of diagnosis but also prognosis.

Please remember the opinions expressed on Patient Power are not necessarily the views of our sponsors, contributors, partners or Patient Power. Our discussions are not a substitute for seeking medical advice or care from your own doctor. That’s how you’ll get care that’s most appropriate for you. 

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Page last updated on October 6, 2017