Srdan Verstovsek, MD PhD; Jamile M. Shammo, MD; and Ruben Mesa, MD
Srdan Verstovsek, MD, PhD; Jamile M. Shammo, MD; and Ruben Mesa, MD, review the triggers to begin treatment for polycythemia vera and the goals of therapy.
Srdan Verstovsek, MD, PhD: Once we are sure that the patient has polycythemia vera, we fulfill diagnostic criteria. The next question is whether or not the patient needs therapy. Now, all the patients are at risk of blood clotting if they have an uncontrolled red blood cell count. It is a standard practice to do a phlebotomy, or blood-letting, to decrease the hematocrit, the measure of the red blood cells in the patient’s blood, to below 45%. It is now very well established in prospective randomized studies that that should be the goal of therapy: to maintain the hematocrit below 45%. Almost all the patients are also given baby aspirin, unless there is a contraindication, to make blood flow easier, because of the effects of the aspirin on the blood cells.
The next step is to assess the risk of thrombosis within the patient’s population. There are patients with polycythemia vera who would have a lower risk than the others for a blood clot. And 2 factors are traditionally used to assess that: an age over 60-years or a history of blood clot, which would make a patient at high risk for blood clot. Conversely, if none of this is present, the patient is at lower risk. So, patients with a low risk are usually not treated beyond the phlebotomy and aspirin. But the patients with a high risk are usually given cytoreductive therapy to control the blood cell count.
Jamile M. Shammo, MD: Goals of therapy for patients who have polycythemia vera are probably divided into 2 broad categories, and perhaps they intercorrelate. The first one is to optimize blood parameters and reduce the risk of thrombosis (because these are intercorrelated, again). And then, symptom control. For a patient who is asymptomatic, it’s difficult to say, “Well, I want to control the symptoms,” because sometimes initiation of cytoreductive therapy may be problematic for them, because they will develop symptoms that they didn’t have in the beginning. So, I think we need to determine, what is the goal before you go on treating someone? That, generally speaking, is based on risk stratification and symptomatology. That’s how I would address it, typically.
Leukocytosis has been suggested as one of the factors that could increase the risk of thrombosis disease. It’s never been evaluated in the prospective fashion, but there are several studies that suggested that leukocytosis—not only the risk of thrombosis—may also be associated with an increased risk of myelofibrotic transformation, even acute leukemia, and shortens survival. So, it’s something to be monitoring. And, to me, the way I think about this, is that it’s a reflection of uncontrolled myeloproliferation, basically.
Ruben Mesa, MD: The therapy of polycythemia vera, in 2017, remains at its core a strategy for decreasing the risk of thrombosis and bleeding. We clearly are hopeful that it will have a favorable impact on symptoms, the spleen, and other aspects of the disease, including—in the future—hopefully decreasing the risk of progression. Though, without question, the current therapeutic goal is to decrease that risk of thrombosis and bleeding.
On that basis, we use the risk assessment, which is really around that risk of thrombosis and bleeding, in the selective determination, as to who should have cytoreductive therapy with active medications. All patients with polycythemia vera need to have control of the hematocrit, regardless of what risk strata they fall into. Patients with polycythemia vera are managed with a low-dose aspirin, regardless of their risk strata. So, really, we use that risk strata for determining who should receive cytoreductive therapy.