Harry P. Erba, MD, PhD: I’d like to spend 5 minutes on essential thrombocytopenia [ET] before we get to concluding remarks. Jamile, how do we diagnose ET?

Jamile M. Shammo, MD, FASCP, FACP: There are diagnostic criteria that were set forth by the WHO [World Health Organization]. Essentially, you have to demonstrate clonality of the myeloproliferation, ruling out secondary thrombocytosis and other entities as well. It could be mass PV [polycythemia vera], it could be early myelofibrosis, it could be MPNs [myeloproliferative neoplasms], MDS [myelodysplastic syndrome], ring sideroblasts with thrombocytosis.

It’s important to meet all 4 points—according to the WHO, with platelet counts over 450,000 per mm3—finding bone marrow proliferation of megakaryocytes in clusters that are mildly atypical, finding no or minimal fibrosis, ruling out other entities, and demonstrating clonality in the presence of driver mutation. If there are no driver mutations, then demonstrating other clonal populations by performing a next-generation sequencing panel, which could be done on the bone marrow or the peripheral blood. That’s how ET should be done.

You have to realize that about 10% of the patients with ET may not have driver mutation, in which case it’s important to look at the bone marrow biopsy. I realize it can be really difficult in those instances. I’m sure I have a bunch of patients who have thrombocytosis that is reactive, but I cannot prove the clonal nature of it, yet there is no other reason for it, hence they are stuck with that characterization.

Harry P. Erba, MD, PhD: Krisstina, how do we risk stratify in ET?

Krisstina Gowin, DO: Risk stratification within ET is based on age: 60 years or older is high risk, and younger is lower risk. Additionally, very similarly to polycythemia vera, we’re looking at the risk of prior thrombotic events. What is unique, and this is within the NCCN [National Comprehensive Cancer Network] Guidelines, is that we’re now incorporating the JAK V617F mutation as part of the risk stratification.

Those who are low risk are less than 60 years old, have no thrombotic events, and are JAK negative. Intermediate patients are greater than 60 years old, have no thrombotic events, and have no thrombosis. Higher-risk patients have a history of thrombosis at any age and are JAK positive. This helps to tailor how we treat these patients for low-risk disease.

We focus on managing their vasomotor symptoms, and monitoring for new thrombotic events, or new symptom evolution. With the high-risk disease, we’re focusing more on cytoreduction with hydroxyurea or interferons.

Transcript Edited for Clarity