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What contributes to thrombotic risk in PV?

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Current guidelines for therapy of polycythemia vera aim to normalize the red blood cell count as well as normalize the white blood cell count and platelets along the way. This is important because even on the cytoreductive therapy, we are decreasing the risk of thrombosis, but we are not eliminating it. That may be in part explained by not looking or paying attention to a white blood cell count. We know that the white blood cell count or leukocytosis, particularly progressive leukocytosis, has implications on the thrombotic risk of the patients.

Traditionally, we have been using two factors that would assess the thrombotic risk. That would be age 60 or over or a history of blood clotting. If one or the other is present, then that particular PV patient has a risk of thrombosis and requires introductional cytoreductive therapy – not only a baby aspirin and phlebotomy. The goals of that effort is to normalize the hematocrit below 45% and maintain it below 45% hopefully without any need for phlebotomy. The other factor will be to control progressive leukocytosis. White cell count increase over three or four measurements will certainly identify patients at a high risk of thrombosis. And the final factor would be increased thrombocytosis, increase in platelets where you would also like that to normalize.

A thrombotic episode in PV patient is of a major concern because that leads to increased morbidity and mortality. In other words, complications from having impaired circulation in a body leads to impairment of the organ, which can be a brain or a heart, and also leads to untimely death. Even in the cases of a cytoreductive therapy, although we are reducing the risk of thrombosis, there is still underlying risk of thrombosis.

head shot of Dr Verstovsek
Srdan Verstovsek, MD, PhD Professor MD Anderson Cancer Center | Houston, TX
Dr Verstovsek’s clinical and translational research focuses on the biological analysis and development of new therapies for patients with myeloproliferative neoplasms (MPNs), and he has served as principal investigator in more than 50 clinical trials. He has published over 400 peer-reviewed manuscripts, actively participates in several national patient organizations, and frequently speaks at engagements at MPN-related events across the globe.