warfarin efficacy in cancer patients on long-term anticoagulation neha doshi, pharmd candidate leann...
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Warfarin Efficacy in Cancer
Patients on Long-term
AnticoagulationNeha Doshi, PharmD CandidateLeAnn B. Norris, PharmD, BCPS
P. Brandon Bookstaver, PharmD, BCPSJulie 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
1. If the patient was a new start, or restarted on warfarin, we excluded values within the first 30 days of initiation due to bridging.
2. Given two INR values, we first calculated the time interval (days) between the values.
3. Then, we took the difference of the two INR values and divided it by the time interval to give us x1.
4. Then we took the point at which it became not therapeutic and subtracted from last INR to give us x2.
5. 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 daysINR 3.1 on 1/10/07 Difference of two INR’s: 3.1 – 2.5 = 1.24Difference / Time interval: 1.24 / 9 = 0.06Point at which INR is no longer therapeutic minus last INR: 3 – 2.5 = 0.50.5 / 0.06 = 8.3 days is TTR
Results- Demographics -
Mean age, years 72.1
Gender
Males 17
Females 0
Race
Caucasian 14
Non-Caucasian 3
Mean height, cm179.8
Mean weight, kg 93.2
Mean body mass index, kg/m2 28.9
INR goal 2-3 17
Total of 60 patients screened
17 met study inclusion
N=17
Results- Comorbidities -
0%10%20%30%40%50%60%70%80%90%
100%
Prev
alen
ce
Results- Type of Malignancies -
0% 5% 10% 15% 20% 25% 30% 35%
Breast
Bone
Skin
Lung
Prostate
Leukemia
Colon
Liver
Head/neck
Bladder
Mal
ign
ancy
Typ
e
Percent of Population
Results- Cancer Treatment -
Radiation18%
Surgery40%Hormonal
18%
Chemotherapy24%
Results- TTR & Bleeding Events -
Comparison of Time in Therapeutic Range (TTR) and Bleeding Events
66% 67%
29%12%
0%
20%
40%
60%
80%
100%
120%
Pre-cancer Post-cancer
BleedingeventsTTR
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
AnticoagulationNeha Doshi, PharmD CandidateLeAnn B. Norris, PharmD, BCPS
P. Brandon Bookstaver, PharmD, BCPSJulie Sease, PharmD, BCPS