Understanding Polycythemia Vera

Transcript:Srdan Verstovsek, MD, PhD: Polycythemia vera (PV) is one of the myeloproliferative neoplasms that is manifested primarily by an increase in the red blood cells. Many patients have high white cell counts and platelets. The issue here is that uncontrolled blood cell growth increases the risk of thrombosis. And because of cardiovascular events—thrombosis and, in some cases, hemorrhage—these patients may have increased morbidity and even mortality. Although overall expectations of a life are close to normal, there is some statistical difference between the patients with PV and the normal population. The main cause of death is complications related to thrombosis and bleeding, cardiovascular events. Some patients can progress to myelofibrosis—a small percentage of patients—or even to acute myeloid leukemia. That’s very rare, and that can certainly affect their life expectancy.

Diagnosis of polycythemia vera is a tricky business sometimes. This actually led to a modification of our diagnostic process recently, in April of this year, when a publication from an international group, that leads the efforts to properly diagnose patients with hematological malignancies, published new guidelines. So, at the moment, these three guidelines are really emphasized as necessary for a diagnosis to be made. There are three major factors. The one is elevation in the red blood cell count, the second is performance of the bone marrow biopsy that would show too many cells in the bone marrow, and a third is identification of the molecular marker, like a JAK2 V617F mutation that is present in about 95% of the patients or a JAK2 exon 12 mutation that is present in about 2% or 3% of the patients. These are three major criteria for a diagnosis of polycythemia vera. And the fourth minor criterion is decrease in erythropoietin. This is a growth factor for red blood cells that is typically very low—low normal or below normal—in patients with polycythemia vera because it’s not necessary for red blood cells to grow without control. But it recognizes the uncontrolled growth of red blood cells and shuts down the production of erythropoietin growth factor for red blood cells, so it’s very low. That’s a minor fourth criteria for diagnosis.

Now, let’s emphasize one part of this that is important. The threshold on the red blood cell count, which is measured by hemoglobin or hematocrit, has been decreased in the new guidelines for making a diagnosis. Because, over time, specifically over the last 5 or 6 years, we recognize that many patients may not even have that high a red blood cell count that typically polycythemia vera patients may have. Some patients have somewhat lower numbers in the red blood cells because they develop iron deficiency, which is a common finding in polycythemia vera. Iron is utilized by red blood cells, and many patients are discovered to have a somewhat lower red blood cell count with iron deficiency without detectable or very low erythropoietin and still have PV. So, one needs to be very cautious and understand the diagnostic process and all the required parts.

Daniel J. DeAngelo, MD, PhD: When treating a patient with polycythemia vera, the goals of therapy are to reduce the risk of thrombosis and the development of cardiovascular and cerebrovascular disease. Unfortunately, right now, we’re unclear as to how to reduce the risk of transformation to myelofibrosis, for example, or transformation to acute leukemia. Those disease-modifying factors really, for right now, cannot be controlled. So, the focus of therapy needs to be to reduce the risk of thrombosis in cardiovascular mortality and morbidity. Therefore, initiation of low-dose aspirin has been shown in multiple randomized studies to be advantageous, with one exception: those are those patients with a very high platelet count who have an acquired von Willebrand disorder. It’s very important to test for those patients, specifically in patients with a platelet count greater than 1 million. And then, the development and strict control of the hematocrit has been shown to reduce the risk of not only thrombosis, but both cardiovascular and cerebrovascular morbidity.

Kim-Hien T. Dao, DO, PhD: I’d like to turn and talk about challenges associated with polycythemia vera. There are a couple of things that I’ve encountered in my practice that I think are more widespread. The first one is, in some rural areas without a specialist like a hematologist, these diseases are being managed by their primary care physician. And so, I think it’s very important for these patients who have polycythemia vera to at least visit a specialist at one point and then collaborate with the primary care physician to manage their disease. Because it’s easy to forget that there are hematocrit goals in order to reduce the patient’s risk from thrombotic events. And I think that is something that we need to work on with our primary care specialists and other physicians to help manage these patients better.

Another challenge that we need to do better on is symptom control. Even though the patient’s hematocrit control is optimal, some of these patients have pretty significant symptoms, such as quality-of-life issues with pruritus or itching, fatigue, and also vasomotor symptoms. So, these are symptoms that are hard to control. Often, the treatment that we use or the drugs that we use will actually cause side effects or impact their quality of life in other ways. And so, that’s an unmet need, to really improve these symptoms that are associated with polycythemia vera. We probably need to do better in monitoring their symptoms using these MPN symptom scoring tools, to help monitor how much this is impacting their quality of life and their day-to-day living.

Transcript Edited for Clarity