Understanding the Different Types of Genetic Mutations in MPNs
Dr. Pemmaraju: So this question comes up very frequently, which is, what about these genetic mutations that I may have, and what's the significance of them? So remember in the myeloproliferative neoplasms, MPNs, so PV, ET, myelofibrosis, there are three main driver genetic mutations, if you will. Driver meaning the main driver of the disease process itself. In most of the MPNs, the JAK2 V617F, that's the most common one, that's what most of you have heard of before, that's 95-100%, really, of all patients with polycythemia vera. There are some variants on it. And then about 50-60% of patients with myelofibrosis and ET, and so that gives way to the other two, which are the CALR and the MPL, CALR and MPL making up the majority of the remainder of these mutations in ET and MF. So that's already an important point. If you have the JAK2, that can occur in any of these three, but you're not going to see, normally, CALR and MPL in polycythemia vera, so I think that's one very important point.
Two, in myelofibrosis, where you can have any of these three, there are some of the newer scoring systems which really put into focus these three driver mutations, and amazingly, they have some prognostic significance. And what I mean by that is, independent of some of the other clinical factors, if you have CALR mutation alone with your myelofibrosis, you should have what's called a better overall prognosis or outcome compared to someone with JAK2 or MPL, which would have a more intermediate prognosis. And then unfortunately there is something called the triple-negative disease, which means you don't have any of these three, likely you have some other deeper mutations such as ASXL1 or others, and that's driving your outcomes in that subcategory to be worse. These are general, right? Every patient is different. There are many other risk factors and clinical factors that we know, but this is one way to think about JAK2, CALR, and MPL in the modern era.
