Clinical trials have pointed a way toward treatment of essential thrombocythemia (ET), a rare, incurable cancer caused by massive overproduction of blood platelets. But the use and benefit of the therapy, hydroxyurea (HU), which suppresses formation of blood cells, had never been studied in a “real world” setting. Researchers at Yale Cancer Center now report that HU significantly reduces risk of thrombotic events including venous thrombosis, strokes, and heart attacks and lowers death rates in patients who use it.
The study is published in the March issue of the Journal of the National Comprehensive Cancer Network (JNCCN). Researchers discovered more than 25% of patients at highest risk of complications from ET were not treated with HU.
“Clinical trials are one thing, but how patients are treated in doctors’ offices across the country is another,” said the study’s lead investigator, Nikolai A. Podoltsev, MD, PhD, a hematology expert at Smilow Cancer Hospital and assistant professor of medicine (hematology) at Yale Cancer Center. “Based on this analysis, HU can be a life-saving therapy for patients at high-risk of serious complications from essential thrombocythemia.”
In ET, patients’ bone marrow, which is “the factory” for all blood cells, overproduces platelets resulting in a significantly higher risk of “thrombotic events” — venous (like deep vein thrombosis and pulmonary embolism), as well as arterial (like stroke and heart attack). In addition, there is also excessive risk of bleeding. HU puts a brake, of sorts, on platelet production.
The analysis looked at 1010 patients diagnosed with high-risk ET — risk is determined by age older than 60 years with all studied patients being 66 years or older with median age of 79. In this group, 745 (73.8%) of patients received HU. The remaining 26.2% did not. Treatment with the drug was associated with a 48% lower risk of death. Furthermore, every 10% increase in HU daily use was linked with a 12% decreased risk of death.
At the end of study (patients were followed on average for almost three years), 36.2% of HU users and 60.4 percent of non-users died. The median survival was 5.85 years and 2.8 years for HU users and non-user, respectively. Patients treated with HU also had a 49% lower risk of developing arterial and venous blood clots.
The data was pulled from the SEER-Medicare database, developed by the National Cancer Institute and the Centers for Medicare and Medicaid Services. (The SEER registries are nationally representative and account for approximately 28% of the US population.) This database links information on new cancer diagnosis from SEER registries to Medicare enrollment, which includes claims for inpatient and outpatient care and drug prescription. This study covers newly diagnosed ET cases from 2007-2013.
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, Steven D. Gore, M.D., Amy Davidoff, Ph.D., Mengxin Zhu, Rong Wang, Ph.D., and Xiaoyi Wang. Study investigators are also members of Yale Cancer Outcomes Public Policy, and Effectiveness Research Center (COPPER), which aims to improve cancer care and to decrease the burden of cancer on individual patients as well as society.
This research was supported by the Frederick A. DeLuca Foundation.