CO015 | EVOLUTION OF ANTICOAGULANT THERAPY FOR CANCER-ASSOCIATED THROMBOSIS: THE START2 REGISTRY ONCO-VTE LONGITUDINAL STUDY

M. Marchetti^1|2, T. Zollner^1|2, O.C. Cretu^1|2, A. Chistolini³, R. Pancani⁴, L. Puccetti⁵, P. Sivera⁶, W. Ageno⁷, G. Elmi⁸, V. Fregoni⁹, V. Tonelli¹⁰, E. Antonucci¹¹, D. Poli^11|12, A. Falanga^1|2, L. Barcella^1|2 | ¹Hemostasis & Thrombosis Center, Department of Transfusion Medicine, Papa Giovanni XXIII Hospital, Bergamo, Italy; ²ERN EuroBloodNet; ³Hematology Unit, Department of Translational and Precision Medicine, Sapienza University of Roma, Roma, Italy; ⁴Pulmonary Unit, Hospital of Siena, University of Siena, Siena, Italy; ⁵Hemostasis and Thrombosis Unit, Hospital of Siena, University of Siena, Siena, Italy; ⁶Haematology Unit, Ordine Mauriziano Hospital, Torino, Italy; ⁷Department of Medicine, University of Padua, Padova, Italy; ⁸Department of Medicine, Maggiore Hospital, Bologna, Italy; ⁹Department of Medicine, Sondalo Hospital, Sondalo, Italy; ¹⁰Angiology Unit, Sant'Eugenio Hospital, Roma, Italy; ¹¹Arianna Anticoagulazione Foundation, Bologna, Italy; ¹²Department of Critical Care Medicine, Thrombosis Centre, Azienda Ospedaliera Universitaria Careggi, Firenze, Italy

Background. Managing anticoagulant therapy in cancer-associated thrombosis (CAT) remains a clinical challenge, balanced between the heightened risks of recurrent venous thromboembolism (VTE) and major bleeding. The START2 Registry ONCO-VTE provides prospective, real-world evidence from patients with active malignancies, tracking the transition of clinical practice toward direct oral anticoagulants (DOACs).
Objectives. This study characterizes the CAT patient population and assesses temporal changes in prescription trends and clinical outcomes by comparing two distinct enrollment windows: January 2022–April 2024 (Group 1) and April 2024–December 2025 (Group 2).
Methods. Data from 333 patients (extracted as of Dec. 18, 2025) were analyzed. Group 1 comprised 270 patients, while Group 2 included 63 patients enrolled via the REDCap platform. Primary endpoints focused on anticoagulant selection, VTE recurrence, major bleeding events, and all-cause mortality.
Results. The median age of the cohort was 69 years (29% aged ≥75). Over a median follow-up of 12 months (14 months for Group 1; 6 months for Group 2), solid tumors—primarily lung (18%) and colorectal (13%)—were the most prevalent. Deep vein thrombosis was the leading index event (52%), with 35% of all events being incidentally detected. Comorbidities such as hypertension (47%) and cardiovascular disease (11%) were frequent. A clear shift in treatment was observed: DOAC use rose from 59% in Group 1 to 64% in Group 2, while parenteral anticoagulant use (LMWH/Fondaparinux) declined from nearly 40% to 34%. Across the full cohort, VTE recurrence and major bleeding occurred in 7.5% and 6.6% of patients, respectively. In a balanced subgroup analysis (≥6 months follow-up, n=227), Group 2 showed a significant reduction in major bleeding compared to Group 1 (7.1% vs. 11.2%), despite similar VTE recurrence rates (7.1% vs. 8.1%).
Conclusions. Analysis of the START2 ONCO-VTE registry highlights a growing preference for DOACs in real-world oncology. This evolution in prescribing patterns is associated with a significant reduction in major bleeding events without loss of antithrombotic protection. These results suggest that modern management strategies provide a high degree of safety and efficacy, even within this fragile patient population.