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Speaker Disclosure
National Institutes of Health
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22 slide(s)
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Abstract
Thromboembolic disease is a well recognized complication of cancer. Patients with cancer experience venous thromboembolic events at a rate 4 to 7 times higher than that of the general population. An analysis of the association of venous thromboembolic disease and cancer revealed that thrombosis often is the presenting sign of cancer. Although all tumor types are associated with thrombosis, glioblastoma and carcinomas of the ovary and pancreas are consistently associated with the highest incidence of venous thromboembolic events.
Despite the strong association between malignant disease and thromboembolic disorders, the molecular and cellular basis of this relationship remains uncertain. Hypotheses regarding the mechanism have included the activation of blood coagulation by tissue factor in tumors, a factor X-activating cysteine protease, mucinous glycoproteins, and MET oncogene activation. Laboratory markers of coagulation activation are often elevated in patients with cancer but are of little clinical utility in assessing individual risk for thrombosis. We have evaluated the hypothesis that elevated numbers of tumor-derived tissue factor microparticles in plasma contribute to cancer-associated thrombosis.
We have developed novel instrumention for the sizing and detection of blood microparticles using impedance-based flow cytometry. With NPE Systems, we have developed a flow cytometer that measures particle size by impedance, not light scattering, using a flow cytometer in which particle sizing is based on the Coulter principle--the measurement of particle size by changes in impedance induced when a particle passes through a small pore. Our goal has been to develop this novel instrumentation specifically for microparticle quantitation, sizing and fluorescence.
Using this instrument, we have shown using impedance-based flow cytometry that elevated numbers of tissue factor-bearing microparticles are associated with certain forms of cancer. Using a high affinity antibody to tissue factor, tissue factor-bearing microparticles were measured in platelet-poor plasma derived from normal subjects and patients with a variety of different forms of advanced cancer using impedance-based flow cytometry. The pattern of these microparticles in these samples indicates median diameters of about 350-500 nm, with a range from 200-800 nm.
Tissue factor-bearing microparticles were measured in platelet-poor plasma derived from normal subjects and patients with advanced cancer. In the patients studied, tissue factor-bearing microparticles were found in about one-third of patients, including patients with pancreatic carcinoma, ovarian carcinoma, colon cancer, and breast cancer. Pancreatic cancer, which ranks among the malignancies associated with the highest rates of thrombosis, was studied in subjects with surgically unresectable or metastatic disease. Tissue factor bearing microparticles were detected in significantly more subjects with pancreatic cancer (approximately 260%) than healthy individuals in whom tissue factor-bearing microparticles remained below the level of detection in all but about 15%. Three patients with pancreatic cancer underwent curative surgery and had almost total elimination of tissue factor microparticles, suggesting that these microparticles are tumor-derived. These results indicate that tissue factor-bearing microparticles are present in the plasma of many patients with advanced cancer, and particularly pancreatic cancer.
Thrombosis is the second leading cause of death in patients with cancer. Employing impedance-based flow cytometry in which the size and number of bloodborne microparticles in plasma can be determined, we measured the concentration of tissue factor-bearing microparticles in a clinical trial to evaluate the hypothesis that tissue factor microparticles are a risk factor for the development of cancer-associated thrombosis. The number of tissue factor-bearing microparticles was assessed in four cohorts: (1) healthy individuals; (2) cancer patients without venous thromboembolic events; (3) cancer patients with an acute venous thromboembolic events within 72 hours of diagnosis; (4) individuals with acute idiopathic venous thromboembolic events without cancer. Cancer patients with an acute venous thromboembolic events were more than four times as likely to have detectable tissue factor-bearing microparticles compared to a group of age, stage, sex, and diagnosis-matched controls. Few individuals with an idiopathic venous thromboembolic events had measurable tissue factor-bearing microparticles compared with the cancer patients with acute venous thromboembolic events. These data suggest that tissue factor-bearing microparticles may be responsible for the hypercoagulable state in some patients with cancer-associated thrombosis. Monitoring tissue factor-bearing microparticles in patients presenting with venous thromboembolic events might assist in discriminating those with occult malignancy from those with idiopathic venous thromboembolic events and also assist in identifying patients that might benefit from antithrombotic therapy.
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