S174 Abstracts / Thrombosis Research 140S1 (2016) S168–S200 Conclusions: Recurrence of cancer-associated VTE is not uncommon, and the treatment of VTE has significant hemorrhagic risks. Our analysis suggests that there is no significant difference in the rate of VTE recurrence and anticoagulant-related bleeding when using oral DOACs versus LMWH. Further studies are needed to compare the safety and effectiveness of these methods of anticoagulation. OC-14 Baseline D-dimer levels are predictive of recurrent venous thromboembolism (VTE) at 6 months in cancer patients with VTE treated with tinzaparin C.I. Piatek 1 , S.T. Tagawa 2 , D. Wei-Tsai 3 , D. Hanna 1 , I.C. Weitz 1 , C. O’Connell 1 , L. Rochanda 1 , S. Groshen 3 , H.A. Liebman 1 1 Jane Anne Nohl Division of Hematology, Keck School of Medicine University of Southern California, Los Angeles, California, 2 Weill Medical College of Cornell University, New York, 3 Department of Biostatistics, Keck School of Medicine University of Southern California, Los Angeles, California; USA Introduction: VTE is a major complication in cancer patients. Despite treatment with low molecular weight heparin (LMWH), 9% will have recurrent VTE within 6 months. Measurement of plasma biomarkers in cancer patients receiving LMWH may be predictive of recurrent VTE or overall survival (OS). Aim: We conducted a single arm phase 2 study to evaluate the efficacy and safety of once daily tinzaparin for the initial treatment and extended prophylaxis of VTE in cancer patients. The study included a prospective analysis of plasma biomarkers D-dimer and IL-6 to assess whether these were predictive of recurrent VTE or OS. Materials and Methods: Consecutive patients with active cancer diagnosed with a pulmonary embolism (PE) and/or proximal deep venous thrombosis (DVT) at the University of Southern California Norris Comprehensive Cancer Center, Los Angeles County Medical Center, or New York Presbyterian – Weill Cornell Medical Center were invited to participate in this study with a target enrollment of 100 patients. Key eligibility criteria included: age ≥18, ECOG score ≤2, adequate organ function, and ≥6 month estimated survival. Patients were treated with daily subcutaneously tinzaparin 175 U/kg for 6 months on study. Tinzaparin could be continued ≤1 year at the discretion of the treating physician. All patients who received ≥1 dose were evaluable for efficacy and safety. Primary study endpoints were recurrent VTE or major bleeding. Secondary outcome measures included OS and plasma biomarkers. Biomarkers were measured at baseline, 7 days, 1 month and 6 months after tinzaparin initiation. Patients who had baseline and 1 week or 1 month samples collected were included in the biomarker analysis. Results: 97 patients were enrolled. 2 patients were ineligible. 8 patients did not have baseline or follow-up biomarkers completed. 87 patients were included in the analysis. 28 (32%) of patients completed ≥ 6 months of tinzaparin. Major bleeding occurred in 2 patients. 11 patients had recurrent VTE at 6 months (3 PE, 7 DVT, 1 central venous thrombosis not associated with a catheter). Median baseline D-dimer level was 2759 ng/mL (range: 375-37,591). Median baseline IL-6 level was 9.4 pg/mL (range: 0.8-20.9). Baseline D-dimer > median was predictive of VTE recurrence at 6 months (p = .006). Baseline IL-6 > median was not predictive of VTE recurrence at 6 months. Neither 1 month D-dimer or IL-6 levels were predictive of VTE recurrence at 6 months. D-dimer and IL-6 at baseline and at 1 month were not predictive of OS. Conclusions: In patients with active cancer and VTE treated with tinzaparin, baseline D-dimer levels above the median value were predictive of VTE recurrence at 6 months. Plenary Session 8: Open questions in cancer and thrombosis OC-15 Risk factors for cancer development after idiopathic venous thromboembolism B. Cosmi 1 , C. Legnani 1 , A. Ghirarduzzi 2 , V. De Micheli 3 , V. Pengo 4 , S. Testa 5 , D. Poli 6 , E. Antonucci 6 , D. Prisco 6 , A. Tripodi 7 , P. Prandoni 8 , G. Palareti 1 (on behalf of FCSA, Italian Federation of Anticoagulation Clinics) 1 Dept. Angiology & Blood Coagulation, University Hospital S. Orsola-Malpighi, Bologna, 2 Dept. Internal Medicine I, Angiology, Arcispedale Santa Maria Nuova, Reggio Emilia, 3 Haemostasis and Thrombosis Centre, Hospital of Lecco, 4 Dept. of Cardiothoracic and Vascular Sciences, University Hospital of Padua, 5 Haemostasis & Thrombosis Center, General Hospital, Cremona, 6 Thrombosis Centre, Dept. Heart and Vessels, University Hospital of Florence, 7 Angelo Bianchi Bonomi Hemophilia & Thrombosis Center, Dept. Internal Medicine, University & IRCCS Maggiore Hospital, Milan, 8 Internal Medicine, Dept. of Medical and Surgical Sciences, University Hospital of Padua; Italy Introduction: Idiopathic venous thromboembolism (VTE) is associated with the risk of cancer but the risk factors for cancer development in such patients are still uncertain. Aim: To assess risk factors for the development of cancer after a standard course of anticoagulation in patients with first episode of idiopathic VTE. Materials and Methods: Subjects were enrolled in the three large prospective multicentre studies: PROLONG (NEJM 2006) PROLONG II (Blood 2010) and DULCIS (Blood 2014). Women whose index event was hormone related were excluded from the analysis. The development of cancer was recorded during a 2-year follow-up. Results: 1,805 patients were enrolled (M/F: 510/453), mean age: 62, median: 67; range:18-87 years). Cancer developed in 55 patients (3% ; 1.7% pt-years) of whom 15 (2.0%; 1.1 % pt-years) had PE with or without DVT and 40 (3.8%; 2.1% pt-years) had DVT without PE (p=0.03). The development of cancer was associated with DVT without PE (HR:1.8; 95% CI: 1.1-3.3) and age >65 (HR: 2.5; 95%: 1.3-4.9). Among patients with DVT, with or without PE, the development of cancer was associated with the presence of residual vein obstruction > 4 mm (RVO) at compression ultrasound (HR: 1.8, 95% CI: 1.1-3.3) and age > 65 (HR: 2.8; 95% CI: 1.3-6.2). Conclusions: Age > 65 years, DVT without PE and the presence of RVO are significantly associated with the risk of developing cancer after a first episode of idiopathic VTE over a two-year follow-up. OC-16 Neutrophil extracellular traps and tissue factor-bearing microvesicles: a liaison dangereuse causing overt DIC in cancer patients? L. Hell 1 , J. Thaler 1 , K. Martinod 2,3,4 , C. Ay 1 , F. Posch 1 , D.D. Wagner 2,3,4 , I. Pabinger 1 1 Clinical Division of Haematology and Haemostaseology, Department of Medicine I, Medical University of Vienna; Austria, 2 Program in Cellular and Molecular Medicine, Boston Children‘s Hospital, 3 Department of Pediatrics, Harvard Medical School, 4 Division of Hematology/Oncology, Boston Children’s Hospital; Boston, Massachusetts, USA Introduction: Overt disseminated intravascular coagulation (DIC) is a systemic process characterized by excessive coagulation activation and fibrinolysis that may occur in cancer patients. The underlying patho- mechanisms are still poorly understood. Recent experimental studies found an important role for the interaction between procoagulant neutrophil extracellular traps (NETs) and tissue factor (TF) in the pathogenesis of thrombosis. Aim: To investigate whether NETs and TF-bearing microvesicles (MVs) play a central role in cancer-related overt DIC. Materials and Methods: Twenty-eight cancer patients with overt DIC (ISTH score ≥5, 14 females, median age: 62 years [range: 21-80], 13 with solid tumors, 15 with acute leukemia) and 28 matched healthy controls were