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Warfarin Efficacy in Cancer Patients on Long-term Anticoagulation. Neha Doshi, PharmD Candidate LeAnn B. Norris, PharmD, BCPS P. Brandon Bookstaver, PharmD, BCPS Julie Sease, PharmD, BCPS. Background.
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Warfarin Efficacy in Cancer Patients on Long-term Anticoagulation Neha Doshi, PharmD Candidate LeAnn B. Norris, PharmD, BCPS P. Brandon Bookstaver, PharmD, BCPS Julie Sease, PharmD, BCPS
Background • “Patients with cancer are at high risk to develop venous thromboembolisms, and they are also more likely to develop complications from anticoagulant treatment” • Presence of malignancy increases risk of VTE by a factor of 4 to 6 • Up to 25% of patients with a malignancy will develop thrombosis • Cancer patients constitute 15-20% of patients diagnosed with a VTE Brose KMJ, et al. Curr Oncol 2008;15(1):S58-67.
Background • Annual risk of recurrent VTE is 21-27% • Annual risk of major bleeding is 12-13% • Thromboembolic events = second leading cause of death in cancer patients Brose KMJ, et al. Curr Oncol 2008;15(1):S58-67. 2006 NCCN - Clinical Practice Guidelines in oncology-versus thromboembolic disease. Rose AJ, et al. Soc Gen Int Med 2007;22:997-1002.
Primary Factors • Various factors contribute to the increased risk of thromboembolic and hemorrhagic events3 • Active cancer • Catheters • Prolonged bed rest • Chemotherapy • Hormone therapy Lee AY, et al. Circulation 2003;107:117-21.
Objective • Purpose • Assess the effectiveness of warfarin in a population of cancer patients • Outcome • Determine the proportion of time spent within INR goal • Assess the rate of thromboembolic and major hemorrhagic events
Patient Selection • Documented cancer diagnosis • Active anticoagulation • Any indication • At least 6 months prior to diagnosis • 1 year after diagnosis
Methods • Patient demographics • Primary indication for anticoagulation • Underlying comorbidities • Type of malignancy • Cancer treatment • INR values • Bleeding events
Time in Therapeutic Range (TTR) • Calculated for each patient, pre- and post- diagnosis • If the patient was a new start, or restarted on warfarin, we excluded values within the first 30 days of initiation due to bridging. • Given two INR values, we first calculated the time interval (days) between the values. • Then, we took the difference of the two INR values and divided it by the time interval to give us x1. • Then we took the point at which it became not therapeutic and subtracted from last INR to give us x2. • Divide x1 by x2 and this gives the amount of days in therapeutic range between the two INR values. Rosendaal FR, et al. Thromb Haemostas 1993;69(3):236-9.
TTR - Calculation Example INR 2.5 on 1/01/07 Time interval: 9 days INR 3.1 on 1/10/07 Difference of two INR’s: 3.1 – 2.5 = 1.24 Difference / Time interval: 1.24 / 9 = 0.06 Point at which INR is no longer therapeutic minus last INR: 3 – 2.5 = 0.5 0.5 / 0.06 = 8.3 days is TTR
Results- Demographics - N=17 Total of 60 patients screened 17 met study inclusion
Limitations • Short observation period • Small population • Isolated VA population (100% males)
Conclusions • Chemotherapy was only group with better pre-cancer TTR • Post-cancer TTR was better than pre-cancer TTR • Increased hospital visitations allowing for closer observation and adjustment • LMWH vs. warfarin • LMWH superior in efficacy and convenience, fewer drug interactions, and less hemorrhagic and thromboembolic events • Guidelines indicate LMWH is first line for cancer patients with primary or recurrent VTE
Warfarin Efficacy in Cancer Patients on Long-term Anticoagulation Neha Doshi, PharmD Candidate LeAnn B. Norris, PharmD, BCPS P. Brandon Bookstaver, PharmD, BCPS Julie Sease, PharmD, BCPS