Prophylactic Anticoagulation in Isolated Tumor Thrombus: A Single-Center Retrospective Cohort Study.

Background The optimal management of isolated tumor thrombus (TT) remains unknown. Although therapeutic anticoagulation is indicated for concurrent bland thrombosis or history of venous thromboembolism, current guidelines do not specifically address isolated TT, and recent studies have not shown consistent benefit of anticoagulation in this setting. Objectives To describe the characteristics of patients with isolated TT managed at Gustave Roussy Comprehensive Cancer Center over five years and to explore outcomes, including overall survival, thrombotic events, and bleeding, across different anticoagulation strategies. Methods This retrospective single-center cohort study included consecutive adults with imaging-confirmed isolated TT managed at Gustave Roussy from November 2018 to June 2024. Patients receiving therapeutic anticoagulation for any indication were excluded. The primary outcome was overall survival. Secondary outcomes were incident thromboembolic events and bleeding. Results Among 1,262 screened records, 29 patients with isolated TT met eligibility criteria (mean age 55.6 ± 15.7 years; 75.9% male; 93.1% had stage IV cancer). Ten received prophylactic-dose anticoagulation and 19 received no anticoagulation. Restricted mean overall survival was 50.7 months (95% CI, 43.3–58.06) in the prophylactic anticoagulation group vs. 20.8 months (95% CI, 10.8–30.9) in the no anticoagulation group . New bland thrombosis and bleeding events were infrequent and did not differ significantly between groups. Conclusion In this small retrospective cohort, longer survival was observed in patients receiving prophylactic-dose anticoagulation. This finding may reflect residual confounding and selection of patients with more favorable prognosis rather than a true therapeutic effect and should therefore be interpreted with considerable caution.