Essential Thrombocythemia: Treatment Optimization


Harry P. Erba, MD, PhD: Krisstina, we know that there are some patients with ET [essential thrombocytopenia], especially young women, who can present with a high platelet count and be completely asymptomatic. However, is there a platelet count at which you need to intervene? You’ve focused on thrombotic risk; how about bleeding risk?

Krisstina Gowin, DO: At the higher levels of thrombocytosis, you certainly get a potential risk of acquired von Willebrand factor and a risk of hemorrhagic complications. No, the answer is that there is not a magic platelet number. In those patients, you can safely monitor the platelet count and think about if there are thrombotic events. In those who are high risk, you think about cytoreduction with high platelet counts before initiating aspirin.

Harry P. Erba, MD, PhD: High-risk does include a platelet count over 1.5 million mm3, doesn’t it? Or does it? To say that they should get cytoreductive therapy, Jamile, what do you think about that?

Jamile M. Shammo, MD, FASCP, FACP: Platelet count was considered in the high-risk population, but after finding out about the molecular mutations, patients who have CALR, for example, can present with a high platelet count. Those are the people, by the way, who end up bleeding because even though they know this disease, everybody thinks, “Maybe aspirin,” but that would not be advisable.

In patients who have CALR, even if they have low-risk disease, they have no reason to be on aspirin, especially if they have no prior thrombotic complications. We need to keep that in mind. What I would like to do is get a von Willebrand factor panel making sure that we’re not dealing with a von Willebrand before I start my aspirin. If the patient has prior thrombotic events, and you feel like you have to initiate cytoreduction, then this would be the way to go. Hydroxyurea is a go-to drug in this instance. If you have a low-risk disease patient with cardiovascular events and a JAK2, in this instance, then the consideration of aspirin is certainly reasonable because those people tend to have higher thrombotic events.

Granted, when you’re talking about patients who have ET since their leukemic progression, myelofibrotic transformation is the lowest. Assuming we’re identifying ET, not prefibrotic MF [myelofibrosis], then you need to be careful about inducing complications with the treatment. We like to prevent problems, and that would be 1 way to make sure you know what the molecular lesions are, and then treat high-risk patients with cytoreduction plus aspirin, assuming no prior von Willebrand disease.

Harry P. Erba, MD, PhD: The PT-1 study suggested that hydroxyurea was superior to anagrelide?

Jamile M. Shammo, MD, FASCP, FACP: There are some conflicting data on that. Frankly, I have patients who have been on anagrelide with reasonable control of their platelet count. Most people need to realize that anemia can be a consequence of this, cardiac complications could be a consequence, and there are difficulties in obtaining the drug from the manufacturer. If you can get it, there’s probably a small subset of patients who may benefit from it, but I tend to gravitate toward hydroxyurea. I don’t know how other people feel about this.

Harry P. Erba, MD, PhD: Interferon is another option for these patients. Ruben, do you want to say something about that?

Ruben A. Mesa, MD, FACP: It is certainly included in our NCCN [National Comprehensive Cancer Network] Guidelines for ET as a consideration. However, it’s not FDA approved. There is now a pegylatedinterferon study for patients with ET who have failed Hydrea [hydroxyurea]. The study is being led by Srdan and I with many colleagues around the world, randomizing patients between that and anagrelide.

We want people to consider that trial as an option as both a way to obtain interferon but also to be able to definitively answer that question and hopefully get to the status of an FDA-approved therapy for these individuals. Having used a lot of pegylated interferon alpha 2a off-label over the years, it certainly is efficacious, and we showed a nice second-line study through the MPN [myeloproliferative neoplasm] Research Consortium with Ron Hoffman, John Mascarenhas, Abdulraheem Yacoub, and others of that group showing the benefit of that agent.

Transcript Edited for Clarity

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