Using Contemporary Data to Better Classify Blood Clot Risk in Polycythemia Vera Patients

By Sara Bondell - December 08, 2023

Polycythemia vera causes bone marrow to make too many red blood cells. These excess cells thicken blood and slow its flow, which can cause heart attacks, strokes, blood clots and blockages in the pulmonary arteries.

Treatment for the disease focuses on reducing risk for thrombosis, or blood clots, and usually includes blood withdrawals (phlebotomy), aspirin and medications that reduce levels of blood cells. Patients are classified based on their risk for thromboembolic events: Patients under 60 without any prior history of thrombosis are low risk, and patients over 60 and/or those with a prior history of thrombosis are high risk.

However, the data used to create this classification system is more than 50 years old.

Dr. Andrew Kuykendall, hematologist
Dr. Andrew Kuykendall, Malignant Hematology Program

“Patients weren’t treated the same way back then as they are now, and we know a lot about the disease now than we did,” said Dr. Andrew Kuykendall, an oncologist in the Malignant Hematology Program at Moffitt Cancer Center. “There’s also a lot of nuances. So, one of the things we wanted to look at is how often thromboembolic events occur in this patient population using big sets of data that we have available to us now.”

Kuykendall launched a retrospective study using Optum’s de-identified Market Clarity Data, which includes electronic health records on 105 million U.S. patients between 2007 and 2019. The study included more than 20,000 polycythemia vera patients that were classified as low risk or high risk and followed them for on average 4.3 years. The team looked at the rate of thrombosis for all patients and broke up the high-risk group into two categories: age-based high risk and event-based high risk.

The study’s data was presented at this year’s American Society of Hematology meeting and showed overall that 1 in 4 patients with polycythemia vera experienced at least one thromboembolic event. The rate of thromboembolic events was highest among event-based high-risk patients (50%), followed by age-based high-risk (25%) and low-risk patients (13%). The rate of thromboembolic events was more than triple for event-based high-risk patients compared to age-based high-risk patients, and nearly seven times higher compared to low-risk patients.

“What we are ultimately showing is that these are relevant data points using large data sets. The risk for thrombosis is not only very prevalent in super high-risk patients, but also in low-risk patients,” said Kuykendall, who led the study. “We need to be thinking about what we can do to minimize that risk because it’s obviously higher than what we see in the general population.”

That includes using more active therapies in lower risk populations and investigating different approaches that reduce the need for phlebotomy. Kuykendall says it’s also important to better understand the factors that make a patient high or low risk to create more individualized treatment plans for each patient.

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