Common Test Shows Blood Clot Risk for Cancer Patients Getting Chemo
December 05, 2005
University of Rochester Medical Center scientists discovered that a common test given to cancer patients prior to chemotherapy may also indicate the individual’s risk of developing potentially fatal blood clots. This finding will help oncologists predict which patients may also need low doses of blood thinners as a preventive measure.
Blood clots are a frequent occurrence in some people with cancer, because chemotherapy drugs damage blood vessels, making them susceptible to clotting. About 1 percent of all cancer patients experience them.
“That percentage may sound small, but there is a large population of people with cancer who experience blood clots that can be deadly,” said Alok Khorana, M.D., lead author of a study published online by Cancer, a journal published by the American Cancer Society. Khorana is an assistant professor at Rochester’s James P. Wilmot Cancer Center.
Khorana compared platelet counts – which are taken prior to every chemotherapy infusion to ensure patients can tolerate the treatment – with subsequent blood clot rates. An elevated platelet count put patients at a nearly three-fold risk of developing the clots, according to the report.
“Oncologists routinely check platelet counts and if they see the elevated count, they should be aware of the increased risk of their patients developing clots and monitor them closely,” Khorana says.
Delivering blood thinners to all patients undergoing chemotherapy would not be practical, because of the costs and health risks associated with excessive bleeding. “It’s important to be able to determine which patients are at risk and treat them accordingly,” he said.
The team, which also included Charles W. Francis, M.D., conducted a prospective study of 3,003 newly diagnosed patients treated with chemotherapy between March 2002 and August 2004. The researchers followed patients for up to four cycles of chemotherapy, or two months. These patients are a part of the Awareness of Neutropenia in Cancer Study Group Registry, led by Gary H. Lyman, M.D., M.P.H., director of Health Services and Outcomes Research at the Wilmot Cancer Center.
The study showed blood clots occurred in nearly two percent of patients and incidence was significantly higher for people with lymphoma and stomach, pancreatic and lung cancers.
Patients whose platelet counts exceeded 350,000 per cubic millimeter suffered three-times more blood clots than others with platelet counts of less than 200,000 per cubic millimeter.
Other risk factors associated with the development of clots include the type of cancer and the use of growth factors. Patients who were administered growth factors, designed to treat anemia or boost immune systems, also experienced twice as many blood clots.