ALBERT

Description: Key Points It remains unclear whether a subgroup of high-risk patients could potentially benefit from a more extensive screening strategy. Age, prior provoked VTE, and smoking status may be important predictors of occult cancer detection in patients with first unprovoked VTE.

Description: Venous thromboembolism (VTE), which includes deep vein thrombosis and pulmonary embolism, is a common complication of cancer and is associated with significant morbidity and mortality. Several cancer-related risk factors contribute to the development of VTE including cancer type and stage, chemotherapy, surgery, and patient-related factors such as advanced age and immobilization. Patients with cancer frequently undergo diagnostic imaging scans for cancer staging and treatment response evaluation, which is increasing the underlying risk of VTE detection. The management of cancer-associated VTE is challenging. Over the years, important advances have been made and, recently, randomized controlled trials have been published helping clinicians’ management of this patient population. In this review, we will discuss common cancer-associated VTE scenarios and critically review available evidence to guide treatment decisions.

Description: Obesity has become a major threat to health worldwide. The prevalence of obesity is rapidly increasing, so much so that the World Health Organization has declared obesity as a global epidemic. Obesity is associated with multiple health problems, including venous thromboembolism and atrial fibrillation, both of which are treated with anticoagulation. However, obesity and treatments for obesity such as bariatric surgery can influence absorption, excretion, pharmacokinetics, and pharmacodynamics of various anticoagulants. This results in uncertainty regarding the best antithrombotic strategies in this population, particularly in the morbidly obese. In the recent years, several studies have attempted to investigate anticoagulation use in this population and provided more insight. Herein, we present 4 cases of anticoagulant use in the obese to illustrate the common challenges faced by clinicians and discuss our approach. Whenever possible, we provide a review of the literature and base our recommendations on the best available evidence.

Description: Abstract 3180 Introduction: Pulmonary embolism (PE) is a continuous risk up to 3 months after surgery. Management of anticoagulation can be challenging in those diagnosed with PE after a major surgical procedure. The aim of this study is to evaluate the outcomes and characteristics of patients diagnosed with PE after a major surgery. Methods: A retrospective cohort of consecutive patients with suspected acute PE that underwent computed tomographic pulmonary angiography (CTPA) or lung ventilation/perfusion scans between 1 January 2007 and 31 December 2008 was constructed by two independent investigators by reviewing each patient's diagnostic images. Patients were included in the study if they had a major surgical procedure (admitted to the hospital for more than 24 hours) and developed PE within 12 weeks of the operation. Patients' follow-up for the first 3 months was recorded. Outcomes included major bleeding, as defined by the ISTH guidelines; recurrent venous thromboembolism (VTE), including PE or deep vein thrombosis (DVT); and mortality. The number of days between treatment initiation and major hemorrhage, recurrent VTE, or death, was recorded. Results: Out of the 842 patients diagnosed with PE at the Ottawa Hospital within the timeframe of the study, 160 (19%) were diagnosed during the post-operative period and were eligible for this study. The mean age (SD) in years was 63 (±15.5), 53% were males, 37% had a cancer related surgery, 37% had orthopedic procedures, and 31% had emergency procedures. The mean time (SD) from surgery to PE diagnosis was 13 (±11) days. All patients were followed-up until the end of their treatment; six patients were transferred to end of life care. Initial treatment was low molecular-weight heparin (LMWH) in 124 (78%) patients, unfractionated heparin (UFH) was given intravenously in 27 (17%) patients, and 5 (3%) requiered an inferior vena cava (IVC) filter to be inserted as the initial treatment. During the 90 days of follow up, there were 17 major bleeding events (12%), 6 recurrent VTEs (4%), and 15 deaths (9%). Of the 17 bleeding events, 13 of them (76%) occurred within the first two weeks of initiation of therapy. No bleeding events occurred after the first month. Two patients died (11.7%) from bleeding, one intracranial and one gastrointestinal (GI). Bleeding was from the GI tract in 47% of cases. Of the 5 patients with IVC filters, 3 developed recurrent DVT in the first two weeks after IVC insertion. The other 3 recurrent VTEs occurred on patients receiving anticoagulation. All cause mortality was 8.7% at 3 months. Within the first 14 days, 8 patients died (5%): 3 patients from PE. Outcomes did not vary by type of surgery, initial treatment or by presence of malignancy. Conclusions: Major bleeding is a common and deadly complication in patients diagnosed with PE after a major surgical procedure. The reported rates of bleeding in this population have varied widely in the literature (between 2 to 9%), according to the type of surgery or population. Our results suggest that alternative triaging and treatment strategies may be indicated in these patients. Disclosures: No relevant conflicts of interest to declare.

Description: BACKGROUND: The Sapporo criteria for the diagnosis of the antiphospholipid syndrome (APS) are based on the presence of antiphospholipid antibodies (APLA) and clinical criteria. Although pre-eclampsia, intra-uterine growth restriction (IUGR), late fetal loss and placental abruption, collectively termed “placenta mediated complications”, are recognized as clinical criteria for the APS, their association with APLA remains controversial. OBJECTIVE: This review was conducted to evaluate the association between APLA (anticardiolipin antibodies, lupus anticoagulant, anti B2 glycoprotein 1 antibodies) and placenta mediated complications in untreated women without autoimmune diseases. METHODS: We performed a systematic review of published case-control, cohort and cross sectional studies using MEDLINE (1975 to October week 2 2007), EMBASE 16 (1980 to 2007 week 42) and all EBM Reviews (3rd quarter of 2007). For eligible studies, the rates of adverse pregnancy outcomes were compared between patients with and without specific APLA. Pooled odds ratios with 95% CI were generated using random-effects models. RESULTS: Our search strategy identified 1204 potentially relevant studies. Twenty five were included in the final analysis. Results are outlined in table 1. CONCLUSION: The association between various APLA and pregnancy complications is for the most part weak and inconsistent. There is currently insufficient data to support a significant link between anti-B2 glycoprotein 1 antibodies and pregnancy morbidity. Caution should be used when establishing a diagnosis of APS based on the presence of any APLA, particularly anti-B2 glycoprotein 1 antibodies, in the setting of late pregnancy complications. Table 1 Association Between APLA and Adverse Pregnancy Outcomes Pre-eclampsia OR (95%CI) # studies / participants IUGR OR (95%CI) # studies / participants Placental abruption OR (95%CI) # studies / participants Late fetal loss OR (95%CI) # studies / participants LA: Lupus anticoagulant; aCL: Anticardiolipin antibodies; Anti-B2 GP1 antibodies: Anti-B2 glycoprotein 1 antibodies italic characters indicate statistically significant associations LA 2.88 (1.42, 5.87)
 11 / 6085 3.51 (1.38, 8.93)
 4 / 3232 0.78 (0.13, 4.80)
 2 / 226 3.56 (0.12, 106.05)
 3 / 3870 aCL (IgG/IgM) 1.71 (1.09, 2.70)
 21 / 9722 2.31 (0.74, 7.17)
 6 / 5753 1.35 (0.45, 4.02)
 4 / 1274 3.86 (1.14, 13.07)
 7 / 5963 aCL IgG 1.65 (0.84, 3.22)
 15 / 3627 6.16 (2.50, 15.18)
 2 / 1006 1.87 (0.21, 16.83)
 2 / 500 10.06 (0.88, 114.96)
 2 / 1006 aCL IgM 1.36 (0.93, 1.97)
 13 / 5397 0.75 (0.19, 2.93)
 2 / 3002 0.96 (0.24, 3.85)
 2 / 500 1.37 (0.42, 4.46)
 3 / 3212 anti- B2GP1 (IgG/IgM) 2.97 (0.47, 18.69)
 4 / 2225 20.03 (4.59, 87.43)
 1 / 1108 2.64 (0.14, 50.63)
 1 / 510 6.74 (0.24, 191.23)
 3 / 1828 anti- B2GP1 IgG 0.87 (0.38, 2.01)
 2 / 607 N/A
 0 / 0 N/A
 0 / 0 0.52 (0.02, 11.02)
 1 / 212 anti- B2GP1 IgM 0.37 (0.16, 0.85)
 1 / 400 N/A
 0 / 0 N/A
 0 / 0 1.32 (0.24, 7.42)
 1 / 210

Description: Background: Ambulatory cancer patients at high-risk for venous thromboembolism (VTE) can be identified using a validated risk score. We evaluated the benefit of outpatient thromboprophylaxis with dalteparin in such high-risk patients in a multicenter randomized controlled trial. Methods: Cancer patients at high risk for VTE (Khorana score ≥3) and initiating a new systemic chemotherapy regimen were screened for VTE and, if negative, randomized to either dalteparin 5000 units daily subcutaneously or no prophylactic anticoagulation for 12 weeks. Subjects in both arms were screened with lower extremity ultrasounds every 4 weeks on study. Primary efficacy endpoint was any VTE over 12 weeks and primary safety endpoint was clinically relevant bleeding events over 13 weeks. The study was terminated due to poor accrual. Results: Of 117 enrolled patients, 19 were not randomized due to the presence of VTE on initial screening (N=10, 8.5%) or for other reasons (N=9). The mean age was 59 years with 46% female and 54% male, similar in both arms. The most common primary sites of cancer were pancreas, gastro-esophageal junction, lung and lymphoma. Over three-fourths of patients in each arm had an ECOG performance status of 0 or 1.Of 98 patients randomized, VTE occurred in 12% (N=6/50) of patients on the dalteparin arm and 21% (N=10/48) on the control arm (hazard ratio, HR 0.69, 95% CI 0.23-1.89) (absolute risk reduction 9%, relative risk reduction 42%, number needed to treat = 12). Major bleeding was similar (N=1) in each arm but clinically relevant bleeding was higher in the dalteparin arm (N=7 versus 1 in the control arm) (HR = 7.0, 95% CI 1.2-131.6). There was no difference in overall survival. Conclusions: Thromboprophylaxis is associated with a non-significant reduced risk of VTE with no effect on major bleeding or survival but increased risk of clinically relevant bleeding in this underpowered study population. The Khorana score successfully identifies patients with high incidence of VTE both at baseline and during study. The high incidence of baseline VTE suggests that consideration should be given to screening high-risk patients in clinical practice prior to starting systemic therapy. Future studies should continue to focus on risk-adapted approaches to reduce the burden of VTE in cancer. (Funded by NIH/NHLBI R01HL095109; clinicaltrials.gov identifier: NCT00876915). Table 1. Baseline Characteristics of Patients Enrolled in the PHACS trial Dalteparin Observation Total Enrolled (n) Baseline VTE, n (%) DVT PE Other reasons for not randomizing Randomized (n) Age, mean (SD), y --- --- --- --- --- 50 60 (10) --- --- --- --- --- 48 58 (12) 117 10 (9%) 6* (5%) 4 (3%) 9 98 59 (11) Gender, n (%) Female 21 (42%) 24 (50%) 45 (46%) Male 29 (58%) 24 (50%) 53 (54%) Primary Tumor Site, No. (%) Gynecologic 4 (8%) 4 (8%) 8 (8%) Colorectal 1 (2%) 3 (6%) 4 (4%) GE junction 8 (16%) 4 (8%) 12 (25%) Lung 6 (12%) 7(15%) 13 (27%) Genitourinary 2 (4%) 0 (0%) 2 (2%) Lymphoma 5 (10%) 2 (4%) 7 (15%) Breast 1 (2%) 1 (2%) 2 (2%) Pancreatic 19 (38%) 17 (35%) 36 (37%) Gastric 4 (8%) 6 (13%) 10 (10%) Other 0 (0%) 4 (8%) 4 (4%) Previous history of VTE, n (%) 4 (8%) 2 (4%) 6 (6%) *NOTE: 1 subject had both DVT and PE at baseline screening Abbreviations: DVT, deep vein thrombosis; PE pulmonary embolism; VTE, venous thromboembolism; ECOG: Eastern Cooperative Oncology Group Figure 1. Cumulative Incidence Curves for the Primary Efficacy Outcome in the Intention-to-Treat Population, According to Study Arm. Figure 1. Cumulative Incidence Curves for the Primary Efficacy Outcome in the Intention-to-Treat Population, According to Study Arm. Disclosures Khorana: Leo Pharma: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Boehringer-Ingelheim: Consultancy, Honoraria; Daiichi Sankyo: Consultancy, Honoraria; sanofi: Consultancy, Honoraria. Off Label Use: Randomized trial of dalteparin as prophylaxis. The drug is approved for treatment of cancer-associated thrombosis but not for prophylaxis.. Francis:Eisai: Consultancy, Research Funding; Portola: Consultancy, Honoraria; NHLBI: Consultancy; Lilly: Consultancy. Kuderer:Hospira: Consultancy; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Daiichi Sankyo: Consultancy. Carrier:Leo Pharma: Consultancy, Research Funding; BMS: Research Funding; Bayer: Consultancy, Honoraria; Pfizer: Consultancy. Ortel:Instrumentation Laboratory: Consultancy; Instrumentation Laboratory: Research Funding; Eisai: Research Funding; Daiichi Sankyo: Consultancy. Wun:Janssen: Consultancy. Iyer:Ipsen Pharmaceuticals: Consultancy; Genentec: Research Funding; Bristol Myers Squibb: Honoraria. Lyman:Amgen: Research Funding.

Description: Abstract 3796 Introduction: Systematic reviews have shown that subcutaneous low molecular weight heparins (LMWH) are at least as safe and effective in the treatment of venous thromboembolism (VTE) as intravenous unfractionated heparin (UFH). LMWH allows patients with VTE to be treated as outpatients. However, patients with pulmonary embolism (PE) are still systematically admitted to the hospital for a few days to avoid potential complications. Physicians are reluctant to discharge patients due to insufficient data supporting the safety of outpatient management of PE. This study evaluates the safety of outpatient treatment of acute PE at the Ottawa Hospital. Methods: This is a retrospective cohort study of consecutive patients presenting at the Ottawa Hospital with acute PE diagnosed between January 1, 2007 and December 31, 2008. PE was defined as an arterial filling defect on CTPA or a high probability V/Q scan. Patients diagnosed with PE during hospitalization, patients with chronic PE and patients in whom anticoagulation treatment was not initiated (e.g. palliative care patients, small clinical non-significant PE) were excluded from the analyses. Patients were managed as outpatients if they were hemodynamically stable, did not require supplemental oxygenation and did not have contraindications to low molecular weight heparin therapy. Results: In this cohort of 473 patients with acute PE, 260 (55.0%) were treated as outpatients and 213 (45.0%) were admitted to the hospital. The majority of the patients were admitted because of severe comorbidities (45.5%) or hypoxia (22.1%).No outpatient died of fatal PE during the 3 month follow-up period. At the end of follow-up, the overall mortality was 5.0% (95% CI: 2.7 to 8.4%). The rates of recurrent venous thromboembolism (VTE) in the outpatient group were 0.4% (95% CI: 0.0 to 2.1%) and 3.8% (95% CI: 1.9 to 7.0%) within 14 days and 3 months, respectively. The rates of major bleeding episodes were 0% (95% CI: 0 to 1.4%) and 1.5% (95% CI: 0.4 to 3.9%) within 14 days and 3 months, respectively. Four (1.5%) outpatients were admitted to hospital within the first 14 days because of progressive shortness of breath and pain, a pre-syncopal episode or heparin induced thrombocytopenia. Conclusion: A majority of patients with acute PE can be managed as outpatients with a low risk of mortality, recurrent VTE and major bleeding episodes. Outpatient treatment in PE is feasible and safe in uncomplicated patients. Disclosures: Rodger: Pfizer: Research Funding; Leo Pharma: Research Funding; Sanofi Aventis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Canadian Institutes of Health Research: Research Funding; Heart and Stroke Foundation: Research Funding.

Description: Background The risk of major bleeding in association with perioperative management of vitamin K antagonists is about 3% according to systematic reviews. We performed this study to evaluate the safety of perioperative management of dabigatran using a specified protocol. Methods Patients at least 18 years old, treated with dabigatran and planned for an invasive procedure were eligible for inclusion. The last dose of dabigatran before the procedure was at 24 h (creatinine clearance [CrCl] 〉 50 mL/min and standard bleeding risk), 48 h (CrCl 31-50 mL/h or increased bleeding risk) or 96 h (CrCl 31-50 mL/h and increased bleeding risk). Resumption was in the evening of the procedure with the first dose of 75 mg (hemostasis secured and low bleeding risk), postop day 1, 2 or 3, depending on the complexity of the surgery and consequences of a bleeding complication; all prespecified. Patients were followed for 30 days for major bleeding (primary outcome), minor bleeding, arterial thromboembolism and death and an independent committee adjudicated these events by. We calculated a sample size of 283 cases to exclude a doubling of major bleeding compared to historical warfarin with heparin bridging. The study was funded by Heart and Stroke Foundation Canada. Results We included 286 patients, mean age of 70.6 years (standard deviation, 11.7), 44 (15%) patients had CrCl 31-50 mL/min and 2 (0.7%) had 30 mL/min or less. The planned procedure was considered as “increased bleeding risk” in 102 (36%) patients. The last dose of dabigatran was at 24, 48 and 96 h before surgery in 160, 103 and 23 patients, respectively. Resumption with 75 mg the same day was in 139 patients. Major bleeding occurred in 3 patients (1.05%; 2 adjudicated so far); a 70-year-old male underwent ultrasound-guided drainage of abdomen and was readmitted after 17 days due to rectal bleeding and light headedness; the second patient, an 81-year-old male bled more than expected during the procedure of wide resection of myxosarcoma with free flap rotation and received blood transfusions during surgery, and a 69-year-old male bled 1200 mL during hip revision arthroplasty and received 3 units of red cells. Minor bleeding was observed in 9 adjudicated cases and reported in 10 additional, so far not adjudicated, cases. There were no strokes, systemic emboli, transient ischemic attacks, venous thromboembolic events or deaths. Three serious adverse events were reported (chest pain, congestive heart failure, wound infection) Conclusion With our protocol for perioperative management of dabigatran the risk of major bleeding compares favorably with historical data on vitamin K antagonists. Disclosures: Schulman: Bayer Healthcare: Consultancy, Honoraria, Research Funding; Boehringer Ingelheim: Consultancy, Honoraria, Research Funding. Off Label Use: Dabigatran etexilate is an oral direct thrombin inhibitor approved for the prevention of stroke in patients with atrial fibrillation and (outside the US) for prevention of venous thromboembolism in patients undergoing total hip or knee replacement. This presentation includes discussion of the following off-label use of dabigatran: treatment of venous thromboembolism. Douketis:Boehringer Ingelheim: Consultancy, Honoraria. Lee:Boehringer Ingelheim: Honoraria. Heddle:CIHR: Research Funding; Canadian Blood Services: Membership on an entity’s Board of Directors or advisory committees, Research Funding; Health Canada: Research Funding.

Description: Background: Venous thromboembolism (VTE) may be the earliest sign of cancer. Risk factors associated with the presence of an occult cancer in patients with a first acute unprovoked VTE are unknown. We sought to assess the risk factors predictive of occult cancer detection in patients with a first unprovoked symptomatic VTE. Methods: Post-hoc, pre-defined analyses of the multicenter open-label randomized controlled trial - Screening for Occult Malignancy in Patients with Idiopathic Venous Thromboembolism (SOME) trial (Carrier M et al. N Engl J Med 2015). The trial compared comprehensive computed tomography (cCT) of the abdomen and pelvis in addition to limited occult-cancer screening (complete history and examination, basic laboratory testing, chest radiography, and breast, cervical and prostate cancer screening) with limited occult-cancer screening alone in patients with a first unprovoked episode of VTE. Cox proportional hazard models were used to analyze the effect of specific risk factors on the outcome of occult cancer within 12 months of a diagnosis of unprovoked VTE. Multivariable analysis was performed using Cox proportional hazard models that included all variables that achieved a p value of 〈 0.20 in univariate analyses. Results: A total of 854 patients were randomized to limited occult cancer screening only, or limited occult cancer screening in combination with a cCT. The mean age was 54 years and 67.4% were males. A total of 33 (3.9%; 95% C.I. 2.8-5.4) patients received a new diagnosis of cancer at 12 months follow-up. Age ≥ 60 years, compared to age 〈 60 years, was a predictor of cancer with a corresponding hazard ratio (HR) of 2.90 (95% C.I. 1.44-5.83, p=0.003). A previous provoked VTE in patients was also associated with a higher risk of developing cancer (HR=3.57, 95% C.I. 1.38-9.25, p=0.009). Patients with an unprovoked deep vein thrombosis (DVT), compared to either those with a pulmonary embolism (PE) only or both DVT and PE, seemed more likely to have a diagnosis of cancer. However, this trend was not statistically significant. (Table 1) These results were confirmed on multivariable analysis. Patients exhibiting one of these characteristics had a three-fold higher risk of occult cancer compared with patients without these characteristics. (Table 1) Conclusion: Age at unprovoked VTE diagnosis (≥ 60 years) and prior provoked VTE are predictors of occult cancer, and could potentially be used to identify a group of patients with unprovoked VTE at high risk of underlying cancer. Table 1.Risk factors of occult malignancy among patients with a first unprovoked symptomatic VTE.Patients without cancer (%) (n = 821)Patients with cancer (%) (n = 33)Univariate analysis Hazard Ratio (95% C.I.)P valueMultivariable analysis Hazard Ratio (95% C.I.)P valueAge at diagnosis ≥ 60 years288 (35.1)20 (60.6)2.90 (1.44-5.83)0.0033.0 (1.47-5.99)0.002Male sex555 (67.6)21 (63.6)0.72 (0.35-1.46)0.358--Prior provoked VTE42 (5.1)5 (15.2)3.57 (1.38-9.25)0.0093.8 (1.46-10.03)0.006Type of current VTEDVT only444 (54.3)24 (72.7)1.91 (0.89-4.12)0.0972.1 (0.97-4.51)0.061PE only271 (33.1)7 (21.2)0.60 (0.26-1.38)0.229--DVT + PE103 (12.6)2 (6.1)0.54 (0.13-2.24)0.392--Baseline medicationsOral contraceptive pill48 (5.8)0 (0.0)----Exogenous estrogen18 (2.2)1 (3.0)1.51 (0.21-11.07)0.685--Antiplatelet agent39 (4.8)1 (3.0)0.62 (0.09-4.56)0.641--Oral anticoagulant688 (83.8)26 (78.8)0.66 (0.29-1.53)0.337--LMWH391 (47.7)15 (45.5)0.68 (0.34-1.36)0.275--VTE, venous thromboembolism; DVT, deep vein thrombosis; PE, pulmonary embolism; LMWH, low molecular weight heparin Disclosures Lazo-Langner: Pfizer: Honoraria, Other: Participated in studies funded by this organization, Speakers Bureau; LEO Pharma: Honoraria, Other: Participated in studies funded by this organization; Boehringer Ingelheim: Honoraria, Other: Participated in studies funded by this organization; Bayer: Honoraria, Other: Participated in studies funded by this organization; Daiichi-Sankyo: Other: Participated in studies funded by this organization; Novartis: Other: Participated in studies funded by this organization; Celgene: Other: Participated in studies funded by this organization; Alexion: Research Funding. Shivakumar:Bayer: Honoraria. Routhier:Sanofi-Aventis: Research Funding. Douketis:Janssen: Consultancy; Bristol-Myers Squibb: Consultancy, Honoraria; Pfizer: Honoraria; Sanofi-Aventis: Honoraria; Daiichi-Sankyo: Consultancy; Actelion: Consultancy; Biotie: Other: Advisory board; The Medicines Company: Other: Advisory board; Bayer: Consultancy; Boehringer Ingelheim: Consultancy, Honoraria. Carrier:LEO Pharma: Consultancy, Research Funding; BMS: Research Funding; Bayer: Consultancy; Pfizer: Consultancy.

Description: Abstract 4209 Background: The risk of recurrent venous thromboembolism (VTE) in patients with cancer-associated VTE, remains high even with the use of low molecular weight heparin (LMWH). However, due to the heterogeneity of the disease it is probable that recurrence risk varies widely. We have developed a prediction rule to classify risk of recurrence in the first 6 months of treatment: + 1 is scored for each of female gender, lung cancer and prior VTE and – 1 is scored for breast cancer and – 2 for TNM stage 1 disease. With a score of ≤ 0, 4.5% of patients recur (this represented 48% of the patient populations), and 〉 0, 19.7% recur. The rule was derived in a retrospective cohort study of patients followed at the Thrombosis unit of the Ottawa hospital and requires validation. Methods: We applied our rule in a new set of 819 consecutive patients with cancer-associated VTE from 2 multicentre randomized controlled trials comparing LMWH with vitamin K antagonists (VKA) (ClotCant group). In these studies the stage of disease was not separated by exact TNM classification, rather patients were classified as stage I, II (no metastasis) versus III, IV (metastasis). As such, we redid our derivation model with stage I and II grouped together, which gave this variable a score of – 1. This resulted in a prediction rule which gave a recurrence risk that no longer clearly dichotomized risk; rather gave a low, intermediate, and high risk groups. As in our derivation study, we evaluated patients' risk of recurrence regardless of type of anticoagulant use (VKA or LMWH). Results: Of 819 patients, 86 (10.5%) presented with a VTE recurrence during the anticoagulation period. When we applied our derivation rule in this population, we were able to demonstrate a significant difference in VTE recurrence risk dependent on gender, primary tumour site, stage and history of prior VTE. Patients with a score 〈 0 have low risk (5.1%) for VTE recurrence and this represented 19% of the patient population; patients with a score of 0 had a intermediate risk (9.8%) and this represented 42% of patients; a score ≥ 1 was high risk (13.9%), occurring in 38% of the population. Dichotomizing the results gave a recurrence risk of 8% in patients with a score ≤ 0 and a 15.2% recurrence risk with a score 〉 0. Conclusion: the validation dataset suggests reproducibility of our model. The dichotomized score is less discriminatory than our original model suggesting an advantage to classifying patients tumour stage as TNM stage I versus stage II, III and IV. Unfortunately, we could not test this hypothesis with the ClotCant dataset. Our model appears to differentiate risk for recurrence and should be utilized in treatment trials: attempting novel treatment strategies in high risk patients since LMWH alone does not seem to be enough; and using the less costly typical “LMWH followed by oral anticoagulants” in the low risk population to evaluate whether VKA can be as safe and effective as long term LMWH. Disclosures: Lee: Eisai: Research Funding; Sanofi Aventis: Consultancy, Honoraria; Leo Pharma: Consultancy; Pfizer: Consultancy, Honoraria; Bayer: Honoraria; Boehringer Ingelheim: Consultancy, Honoraria, Speakers Bureau.