Effectiveness of Warfarin among Patients with Cancer
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Among patients treated with warfarin for venous thromboembolism (VTE), cancer patients have more thrombotic and hemorrhagic events than patients without cancer. Is this also the case when cancer patients are anticoagulated for other indications?
The objective of the study is to evaluate the effectiveness of warfarin, given for any indication, among patients with cancer in a community setting.
We identified patients with cancer from a larger prospective cohort of 6,761 patients from 101 clinical sites in the United States, matched to controls without cancer. The proportion of time spent in the therapeutic range, international normalized ration (INR) variability, and the rate of thromboembolic and major hemorrhagic events were compared between the two groups.
Ninety-five patients undergoing treatment for cancer were matched to 283 patients without cancer. The cancer group spent less time in the target INR range (54 vs 66%, P < .001) and had more variable INR values (standard deviation around the mean INR value 1.30 vs 0.71, P < .001). There were more thrombotic events in the cancer group than in the control group (5 vs 0 events, P < .001). These analyses were repeated after excluding all of the patients anticoagulated for VTE; the results were unchanged.
Compared to matched controls, cancer patients receiving warfarin spend less time in the target INR range, have more variable INR values, and have more thrombotic events. These effects are not dependent on whether the patient is anticoagulated for VTE or another indication.
KEY WORDSwarfarin anticoagulation oncology cancer thrombosis
This study was funded by Bristol-Myers Squibb, the makers of Coumadin® brand warfarin. Bristol-Myers Squibb had no role in the design and conduct of the study, or in the collection, analysis, and interpretation of the data, or in the preparation, review, and approval of the manuscript. Dr. Rose is supported by a grant from the Department of Veterans Affairs Office of Academic Affairs. The opinions expressed in this manuscript do not necessarily represent the views or policies of the Department of Veterans Affairs. Dr. Rose is also supported by a Physician Training Award (PTAPM-97-185-04) from the American Cancer Society.
Conflicts of Interest
Dr. Hylek has served as a consultant to and received research support from Bristol-Myers Squibb and AstraZeneca. None of the other authors report any potential conflicts of interest.
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