PO36 | EXTENDED DURATION REDUCED DOSE ANTICOAGULATION IN CANCER-ASSOCIATED THROMBOSIS: A REAL-WORLD COHORT WITH LONG TERM FOLLOW UP

A. Bhide¹, I. Welding¹, O. Ogunbiyi¹, S. Hawkins², E. Greenlay¹, N. Prasannan¹, J. Westwood¹, M. Thomas¹ | ¹Department of Clinical Haematology, University College London Hospital, London; ²Data Clinic, University College London, UK; A. Bhide and I. Welding joint First Authors

Introduction. Clinical practice guidelines on CAT recommend extended-duration anticoagulation beyond 6 months in patients with active cancer/ongoing treatment. However, data on reduced-dose anticoagulation to prevent recurrent CAT are only now emerging.

Aim. This retrospective, single-center observational study reports on the efficacy & safety of extended-duration therapy with reduced-dose anticoagulation in a large real-world cohort of CAT patients.

Methods. Consecutive patients with ongoing review in a dedicated tertiary center CAT clinic from Jan 2019 to Dec 2024 were included. Inclusion criteria: patients with active cancer & VTE who switched to prophylactic dose anticoagulation at the discretion of the treating physician after ≥6 months of full-dose anticoagulation. Data on recurrent VTE (excluding events occurring >48h off anticoagulation), bleeding events, and mortality after anticoagulant dose reduction were collected from electronic health records.

Results. 352 patients had anticoagulant dose reduction at a median of 6.2 months after index VTE (IQR 6-7.4). The most common cancer types were gynecological (26%) & hematological (20%). Index VTE was PE +/- DVT in 63% of patients, isolated DVT in 29.3%, & other sites in 7.7%. 70% of patients had apixaban as secondary thromboprophylaxis, 25% rivaroxaban, and 5% prophylactic dose LMWH. Median follow-up was 15 months (IQR 7-29, range 3-83). Cumulative incidence of recurrent VTE was 2.7% at 12 months 4.9% at 24 months 6.3% at 36 & 48 months and 7.8% at 60 months (Figure 1). 15 recurrent VTE (83%) were symptomatic: 8 (44.4%) were isolated DVT, 4 (22.2%) PE, 3 (16.7%) CVC-associated & 3 (16.7%) other site VTE. 4 (1.1%) patients had major bleeding and 10 (2.8%) had clinically relevant non-major bleeding in the first 12 months (5.1% in the study period). All-cause mortality was 19% in 12 months and 34.7% in the study period.

Conclusions. Rates of recurrent VTE remain reassuringly low in a large real-world cohort when reduced-dose anticoagulation is used for extended-duration secondary prophylaxis after an initial 6-month treatment period with subsequent follow-up for >60 months. Our cohort likely had poorer performance status/more advanced disease than published RCTs based on higher all-cause mortality, better reflecting real-world practice. Bleeding rates were low, although retrospective data collection likely led to underestimation. Further data are required on use of longer-term secondary thromboprophylaxis in an era when people are living longer with advanced cancer.