Newswise — New Haven, Conn. — U.S. and European guidelines on treating Polycythemia Vera (PV), a potentially deadly blood cancer, call for two treatments for patients with high-risk disease: therapeutic phlebotomy and cytoreductive therapy with a drug called hydroxyurea (HU). HU is the most commonly used option, but evidence for HU treatment is limited and both treatments are underused. Now, researchers at Yale Cancer Center (YCC) have documented reduced risk of death and incidence of blood clots in patients receiving those therapies.

The study, published in Blood Advances, represents a “real world” look at the outcomes of high-risk PV patients. Among 820 patients, those treated with phlebotomy had a 35% reduction in death and a 48% reduction in the risk of developing blood clots (thrombosis). For the second treatment, HU, researchers found that every 10% increase in the proportion of days patients used the drug led to an 8% lower risk of death and thrombosis.

PV occurs when a mutation in a gene forces bone marrow to produce too many red blood cells. These excess cells thicken blood, slow its flow, and increase risk of thrombosis. Phlebotomy is therapeutic blood “letting” to reduce blood volume. HU is believed to suppress the ability of bone marrow to produce the excess red blood cells. Thrombosis is the major cause of death among PV patients, and a primary goal of treatment is prevention.

“Our study highlights the value adhering to PV treatment guidelines,” said the study’s lead investigator, Nikolai A. Podoltsev, M.D., Ph.D., a hematology expert at YCC and assistant professor of medicine (hematology) at Yale School of Medicine. “Use of the two recommended treatments saves lives.”

But the analysis also suggests that many patients are not receiving the recommended treatments. In the study, about 39% of patients were undertreated, with more than 16% of patients receiving neither treatment, and 23% receiving only phlebotomy.

“All of the patients we studied were high-risk for clot development, and we now know from our findings that guideline-recommended treatments reduce the risk of both thrombosis and death,” Podoltsev said. “We hope that our research will raise clinicians’ awareness of and adherence to the guidelines and improve the outcomes of PV patients in the future.”

Podoltsev said the patients in the study were treated in contemporary clinical practice — the real world of doctors and patients, not a clinical trial. And they are all at high-risk because of their advanced age. High-risk PV patients are defined by current guidelines as older than 60 and the patients in this research project were 66 or older. The median age was 77.

The data was pulled from the SEER-Medicare database, developed by the National Cancer Institute and the Centers for Medicare and Medicaid Services. This database links information on new cancer diagnoses from SEER registries to Medicare enrollment, which includes claims for inpatient and outpatient care and drug prescription. Since 2001, SEER registries have been required to report PV. This study covers newly diagnosed PV cases from 2007-2013.

Investigators looked for records of thrombotic events, which could occur in veins (including deep-vein thrombosis and pulmonary embolism), arteries (strokes, transient ischemic attack, angina, heart attack, and other events), or manifest as sudden death. They also checked for the use and duration of treatments. (Aspirin is also recommended as a treatment, but data on aspirin use are not available since aspirin is an over-the-counter medication that does not require prescription.)

The study’s senior investigator is Xiaomei Ma, Ph.D., from the Yale School of Public Health. Other study co-authors are Amer M. Zeidan, MBBS, Scott Huntington, M.D., M.P.H., Smith Giri, MBBS, and Steven D. Gore, M.D., from YCC; Mengxin Zhu, M.P.H., Rong Wang, Ph.D., Xiaoyi Wang, M.D., M.P.H., and Amy Davidoff, Ph.D., from the Yale School of Public Health.

This research was supported by the Frederick A. DeLuca Foundation.

About Yale Cancer Center Yale Cancer Center (YCC) is one of only 49 National Cancer Institute (NCI-designated comprehensive cancer) centers in the nation and the only such center in Connecticut. Comprehensive cancer centers play a vital role in the advancement of the NCI’s goal of reducing morbidity and mortality from cancer through scientific research, cancer prevention, and innovative cancer treatment.


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