ALBERT

Description: Background:Polycythemia is the most common adverse effect of testosterone replacement therapy (TRT) and may predispose patients to adverse vascular events. Current Canadian guidelines recommend regular laboratory monitoring and discontinuing TRT or reducing the dose if the hematocrit exceeds 54% (hemoglobin ≥180 g/L). This threshold has been interpreted by some physicians and patients to indicate the need for phlebotomy or blood donation while on TRT. Study Design and Methods: We reviewed all male blood donors in Southwestern Ontario at Canadian Blood Services from December 2013 to March 2016 who self-identified or were found on donor screening to be using TRT in any form. Hemoglobin concentration was measured at the time of donation or clinic visit and with each subsequent appointment in repeat donors. Results:We report a case series of 39 patients on TRT who presented for blood donation over a two-year period. The mean hemoglobin at all donor clinic visits was 173 g/L (range 134-205 g/L, n = 108). Hemoglobin concentrations of ≥180 g/L (calculated hematocrit ≥54%) were measured at 25% of appointments. Of the 27 repeat donors, 12 (44%) had persistently elevated hemoglobin levels (≥180 g/L) at subsequent donations. Conclusions: Hemoglobin concentrations were elevated in blood donors on TRT, with a significant number above levels recommended by current guidelines. These data also suggest that repeat blood donation was insufficient to maintain hematocrit below 54%. Our findings raise concerns about persistent risk of vascular events in these donors, particularly when coupled with the misperception by patients and health care providers that donation has abrogated the risks of TRT-induced polycythemia. Disclosures No relevant conflicts of interest to declare.

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: Abstract 3132 Poster Board III-69 Women with a past history of venous thrombosis are at higher risk for venous thromboembolism (VTE) during and after pregnancy. The highest risk period is the first four weeks post partum. For a woman whose previous event was secondary to a major transient risk factor the antepartum risk of recurrent VTE is low whereas for women whose previous event was idiopathic the antepartum risk is higher. In our institution, for women whose previous event was secondary to a major transient risk factor, standard treatment is to follow closely with no thromboprophylaxis antepartum and then receive either prophylactic low molecular weight heparin (LMWH) or warfarin for six weeks postpartum. For women whose previous event was idiopathic or who were on warfarin at the time of becoming pregnant they receive prophylactic LMWH antepartum with a scheduled delivery and are put back on warfarin if they have long term anticoagulation needs or LMWH for six weeks if they don't have longterm anticoagulation needs. We report the outcome for our patients from 1997 to 2008. All patients were followed for the duration of pregnancy and for 6 weeks postpartum for pregnancy outcome, recurrent VTE, and major bleeding in the thrombosis clinic of London Health Sciences Centre. There were a total of 90 women; 30 women (mean age 30.6 years) with a history of previous secondary thrombosis with 37 pregnancies and 60 women (mean age 29.5 years) with past idiopathic thrombosis with 99 pregnancies. For the secondary group there was 1 episode (2.70%; 95% CI 0.48-13.82) of antepartum recurrent VTE whereas for the idiopathic group there were 3 episodes (3.03%; 95% CI 1.04-8.53). There was no statistical difference between groups (p=1.0). There were no episodes of postpartum VTE recurrence or major hemorrhage for either group. For the secondary group there was 1 fetal loss at 23 weeks (2.7%; 95% CI 0.48-13.82) whereas for the idiopathic group there were 6 fetal losses at 8, 10, 10, 11, 22, 37 weeks gestation (6.06%; 95% CI 2.81-12.60). There was no statistically significant difference between groups (p=0.77). This retrospective review suggests that for pregnant women with a past history of VTE, a strategy of no antepartum prophylaxis for previous secondary thrombosis and antepartum prophylactic LMWH for previous idiopathic thrombosis as well as prophylactic LMWH or warfarin postpartum is efficacious and safe. Disclosures Off Label Use: low molecular weight heparin for prevention of VTE in pregnancy.

Description: Introduction Venous thromboembolism (VTE) occurs in up to 25% of patients undergoing total hip (THA) or knee arthroplasty (TKA) without the use of prophylactic anticoagulation. Low molecular weight heparins (LMWH) are the standard agents for preventing VTE in this setting. In recent years, rivaroxaban, apixaban and dabigatran have been approved for this indication and, although results from randomized trials suggest that they are non-inferior and potentially superior to LMWH, information regarding outcomes in routine use is lacking. Objectives To evaluate the safety and efficacy of rivaroxaban for the prevention of VTE in patients undergoing THR or TKR in routine practice. Methods We conducted a population-based retrospective cohort study using linked healthcare databases in Ontario, Canada, including information on hospital discharge, emergency room visits, medication use, demographics and physician billing. In Ontario older patients have universal drug coverage and thus we included patients aged 66 years or older who received an outpatient prescription for a LMWH, (including dalteparin, tinzaparin and enoxaparin) or rivaroxaban after discharge from THR or TKR between 2002 and 2012 across 121 hospitals. Patients were excluded if they had other indications for anticoagulation. Primary efficacy and safety outcomes in the 30 days after surgery were the occurrence of an Emergency Room visit or hospitalization with a VTE (either deep vein thrombosis or pulmonary embolism) or a hospitalization with non traumatic major hemorrhage, respectively. Secondary outcomes included the previous 2 endpoints at 90 days as well as hospitalization for digestive system endoscopy (a proxy for gastrointestinal hemorrhage) and all cause mortality, both at 30 and 90 days after surgery. Unadjusted and adjusted odds ratios with 95% confidence intervals (CI) were obtained using logistic regression and reported as relative risks (RR) (appropriate given the incidence observed). Results The cohort included 24,321 patients and there was no significant difference on over 35 baseline characteristics between the LMWH (n=11,471) and rivaroxaban (n=12,850) groups. The median age for both groups was 73 years, 14,366 patients were women (59.1%) and 8,612 patients (35.4%) underwent THR. Anticoagulants were prescribed for a median of 14 days after discharge (interquartile range 10 to 21). The main results are shown in the table. Results were consistent in multiple additional analyses accounting for years rivaroxaban was approved in provincial formulary, adjusting for potential confounders, secular trends, individual LMWH, prescriber characteristics, and for subgroup analyses examining THR and TKR separately. Conclusions In this routine practice population-based study, the use of rivaroxaban compared to LMWH was associated with a lower risk of VTE without an increase in bleeding events. Financial Support Canadian Institutes of Health Research; ICES Western Scholars program. Disclosures: Lazo-Langner: Pfizer: Honoraria; Leo Pharma: Honoraria; Boehringer Ingelheim: Honoraria.

Description: Background: Initiation of oral anticoagulant therapy for acute venous thromboembolism requires balancing the need for rapid anticoagulation with the risk of major bleeding. The optimal means of initiating warfarin therapy in the outpatient setting remains controversial. We have previously demonstrated the efficacy of a 10 mg initiation nomogram in comparison to a 5 mg nomogram in a published RCT (Kovacs et al. 2003). Although this nomogram is used in many centres, some are still reluctant to use it due to a fear of potential increased bleeding. Objective: To validate the safety and efficacy of the Kovacs 10 mg warfarin initiation nomogram and to identify patient-specific factors predictive of a maintenance warfarin dose. Methods: We performed a retrospective chart review of 430 consecutive patients who were treated prospectively according to the Kovacs nomogram in the outpatient thromboembolism clinic of a tertiary care hospital. Data were analyzed for 90 days following the initiation of anticoagulation. All patients were treated with standard subcutaneous LMWH for 5 to 7 days and warfarin for a minimum of 3 months. Major bleeding and recurrent venous thromboembolism were defined according to standard criteria. Results: 408 of 430 patients were followed for at least 90 days. Six patients (1.5%) experienced recurrent thrombosis, 3 (1%) suffered a major bleeding event, and 3 (1%) suffered a minor bleeding event requiring treatment with vitamin K. There were no deaths related to thrombosis or bleeding. Three patients died from unrelated causes. Ninety percent of the 297 patients who adhered to the nomogram achieved a therapeutic INR by day 5. Only 8 (2.7%) of patients who adhered to the nomogram had an INR measurement of ≥ 5.0 in the first 8 days of therapy. None of these suffered a major or minor bleed. The most common reason for non-adherence to the nomogram was failure to get an INR test on the days specified, due to the unavailability of testing on weekends and holidays or to patient non-compliance. On univariate analysis, six factors were found to be significantly associated (p 〈 0.05) with the weekly maintenance warfarin dose: Day 3 INR, weight, age, creatinine, gender, and presence of malignancy. The day 3 INR was inversely related to the maintenance dose and was the most predictive factor (R2 = 0.397). Multivariate regression was performed using the above six variables. Gender and presence of malignancy were removed from the model because they did not meet the criteria for significance (p 〈 0.10). Regression using the remaining variables generated the following model: Weekly maintenance dose = 63.835/(Day 3 INR) − 0.265(Age) + 0.115(Weight) − 0.061(Creatinine) + 8.126. R2 = 0.515. Conclusions: The Kovacs 10 mg nomogram results in the rapid achievement of a therapeutic INR without a high incidence of bleeding events. The day 3 INR is strongly predictive of the required maintenance dose. If prospectively validated, our maintenance dose model would provide a simple means of estimating the appropriate maintenance dose using readily available information and without a need for genetic testing.

Description: Background: Acute pulmonary embolism (PE) is a common medical problem in outpatient clinics and emergency rooms. Treatment with heparin and warfarin is well established and effective. In some centres (such as ours) eligible patients with PE are treated as outpatients, however many centres remain reluctant to do so. We review our experience with outpatient treatment of acute PE. Methods: We reviewed hospital charts for all inpatients and thrombosis clinic charts for all outpatients with a diagnosis of acute PE that was made prior to a decision on hospital admission from January 1, 2003 to January 30, 2008. All diagnoses were objectively proven by high probability V/Q scan or non-diagnostic V/Q scan with positive compression U/S or segmental or greater perfusion defect on CTPA. Patients were eligible to be treated as outpatients if they were hemodynamically stable, not high risk for bleeding, not requiring oxygen therapy, not requiring unfractionated heparin due to renal failure, and not having another indication for hospital admission. Most patients were treated with low molecular weight heparin (LMWH) for 5–7 days together with warfarin except for cancer patients who were treated with LMWH alone. All patients were instructed to call the thrombosis service or to go the emergency room if they developed symptoms of new PE or bleeding. Outpatients were seen in follow-up at 1, 4, and 12 weeks in the thrombosis clinic. Inpatient charts were reviewed for demographics and reason for hospital admission. For outpatients, in addition to demographics, charts were reviewed for the three month outcomes of major bleeding, recurrent venous thromboembolism and death. Results: There were a total of 633 patients with PE. 319 were admitted to the hospital whereas 314 (49.7%) were managed entirely as outpatients. The mean age for inpatients was 64 years. Inpatients were admitted for the following reasons: 125 (39%) for concomitant illness, 84 (26%) for hypoxia, 21 (7%) for hemodynamic instability, 14 (4%) for pain control, 1 (0.3%) for thrombolysis, 24 (7%) for other investigations, and 50 (16%) for other or unlcear reasons. For the 314 outpatients the mean age was 55 years and 184 (59%) were female. Eight (2.8%) patients were lost to follow-up. There were 195 (62%) idiopathic PE, 62 (20%) had PE secondary to cancer and 57(18%) to other transient risk factors. There were 247 (79%) patients who were managed with LMWH and warfarin, 51 (16%) managed with LMWH alone and 16 (5%) patients had experimental treatment. At 3 months of follow up there were 3 (1%) patients who developed major hemorrhage (GI bleed, hemoptysis, hemarthrosis), 3 (1%) patients who had objectively documented recurrent thrombosis (1 deep vein thrombosis, 2 PE), and 9 (2.9%) patients died, all of them from cancer progression. None of these events occurred within the first 7 days after diagnosis. Conclusions: To our knowledge this is the largest report of outpatient PE management. In our hospital 50% of ambulatory patients who have a diagnosis of PE are managed entirely as outpatients with a low risk for bleeding or thrombosis recurrence. For those admitted the majority was due to a concomitant illness that required admission itself. Many centres remain hesitant to treat patients with PE in this fashion but will treat patients with deep vein thrombosis as outpatients. Both conditions are at risk of recurrent PE and bleeding but it is not clear how a hospital admission would prevent that from happening. Our findings suggest that uncomplicated PE is not an indication for hospital admission per se. Outpatient management of PE deserves further consideration.

Description: Background. T-Cell Large Granular Lymphocyte Leukemia (T-LGL Leukemia) is an extremely rare lymphoproliferative disorder which can originate from either mature T cells (CD3+) or natural killer cells (CD3-). T-LGL leukemia is a slowly progressing disease, rarely presenting with an aggressive course and in general patients have prolonged survival. Treatment is commonly monotherapy with methotrexate (with or without prednisone), cyclosporine, or cyclophosphamide. Herein we review our experience with the management of T-LGL in the last 15 years. Patients and Methods. We conducted a retrospective cohort study of all patients diagnosed with T-LGL at our center between 2000 and 2015. Patients were included if they had a positive study for T-Cell Receptor gene rearrangement. Response was evaluated using the criteria of Loughran et al (Leukemia 2015). Data was analyzed using descriptive statistics. Results. We included 23 patients, (16 male). All of the patients were caucasian with the exception of two. The average age at diagnosis is 65.1 years. Patients were treated for symptomatic cytopenias or splenomegaly with transfusions and/or chemotherapy. Six patients did not need any treatment. Fourteen of the 23 patients were treated with oral methotrexate monotherapy. The methotrexate dose ranged from 5mg/week to 15mg/week orally. Seven patients had a complete response, 2 had a partial response, 3 patients failed treatment, 1 patient was not evaluable, and 1 was stable. Four patients were treated with methotrexate and prednisone. Two patients obtained a complete response, with 1 partial response, and 1 patient was not evaluable due to the short duration of the prescription. Nine patients were treated with oral cyclophosphamide at doses of 50mg or 100mg po daily. Four patients achieved a complete response, 2 patients achieved a partial response, while the other 3 patients did not respond. Only 2 patients were treated with oral cyclosporine, at 400mg/day and at 500mg/day. One patient failed treatment while the other is still on therapy. Two patients died while on the study at 22 and 42 months, both deaths were due to other illnesses not associated with T-LGL Leukemia. The median time since diagnosis for the remaining patients is 41 months. Conclusion. T-LGL is a rare lymphoproliferative disorder. Most patients responded to simple oral therapy with methotrexate or cyclophosphamide and patients generally have prolonged survivals. Disclosures Lazo-Langner: Bayer: Honoraria; Pfizer: Honoraria. Kovacs:Daiichi Sankyo Pharma: Research Funding; LEO Pharma: Honoraria; Bayer: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding.

Description: Abstract 3110 Background: Patients with hematological malignancies are at increased risk of influenza and its complications. However, evidence for the efficacy of influenza vaccination in this population is limited and contradictory [Pollyea et al., J Clin Oncol. 2010]. The adjuvanted pandemic H1N1 vaccine has been shown to be highly effective in healthy adults, with reported rates of seroprotection and seroconversion of over 90% [Plennevaux et al., Lancet 2010]. We sought to determine whether patients being treated for hematological malignancies were able to mount a protective antibody response to the H1N1 pandemic influenza vaccine. Methods: Patients being treated for hematological malignancies at the London Regional Cancer Program during the 2009–2010 influenza season were invited to participate. Patients who had received the vaccine prior to the commencement of the study in November 2009 were excluded. Pre-vaccination plasma samples were collected in November 2009, and post-vaccination samples were collected from January through March 2010. At the time of second sample collection, patients were asked to complete a questionnaire asking if and when they had received the H1N1 influenza vaccine. Plasma samples from patients who elected not to be vaccinated formed a control group. Antibody titration was performed by the hemagglutinin inhibition test. Our primary outcome was the rate of seroconversion, as defined by a fourfold increase in antibody titres. We also measured geometric mean titres (GMT), geometric mean titre ratios, (GMTR, defined as the ratio of the post-vaccination titre to the pre-vaccination titre), and rates of seroprotection (titre ≥ 1:80). Statistical analysis was done using Mann-Whitney U, chi-squared, or Fisher's Exact Tests, as appropriate. Results: Sixty-two patients received the H1N1 vaccine and 41 patients chose not to be vaccinated. The rate of seroconversion among vaccinated patients was 21%, which was significantly higher than that in unvaccinated patients (0%) and significantly lower than that in healthy individuals. The GMTR was significantly higher in the vaccinated group than the unvaccinated group (2.2 ± 2.5 vs. 1.2 ± 0.6, p = 0.041). There were no significant differences in the geometric mean titres or the rates of seroprotection between the vaccinated and unvaccinated groups. Of the 46 patients on active chemotherapy who received the vaccine, 10 (22%) seroconverted and 16 (35%) mounted seroprotective titres. Of the 12 patients on active Rituximab who received the vaccine, 2 (17%) seroconverted and 4 (33%) mounted seroprotective titres. There were no significant differences in the rates of seroconversion and seroprotection between patients on or off chemotherapy or between patients on or off Rituximab. Conclusions: Only 21% of patients with hematological malignancies were able to produce a fourfold increase in antibody titres in response to the H1N1 influenza vaccine, a rate significantly lower than that previously reported for healthy patients. We were unable to identify any clinical factors predictive of a response to the vaccine. Physicians should be aware that patients with hematological malignancies are less likely to receive protection from the influenza vaccine, and should consider alternate strategies to minimize the morbidity and mortality from influenza in this population. Larger studies are indicated to confirm these results. Disclosures: No relevant conflicts of interest to declare.

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.