PO30 | LONG-TERM ANTICOAGULANT THERAPY AND PREVENTION OF RECURRENT VENOUS THROMBOEMBOLISM IN ADVANCED OVARIAN CANCER

V. Bitsadze ¹, A. Vorobev ¹, J. Khizroeva ¹, A. Solopova ¹, M. Tretyakova ¹, N. Gashimova ¹, K. Grigoreva ¹, A. Khisamieva ¹, J. Gris ^1|2, I. Elalamy^1|3|4, G. Gerotziafas^1|3|4, A. Makatsariya¹ | ¹Department of Obstetrics, Gynecology and Perinatal Medicine, N. F. Filatov Clinical Institute of Children’s Health, I. M. Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia; ²Faculty of Pharmaceutical and Biological Sciences, Montpellier University, France; ³Department Hematology and Thrombosis Center, Medicine Sorbonne University, Paris, France; ⁴Hospital Tenon, Paris, France

Background. Advanced ovarian cancer is characterized by persistent activation of the coagulation system due to tumor-associated inflammation, endothelial dysfunction, and ongoing antitumor treatment. After an initial VTE, the risk of recurrence remains elevated for several years.

Aim. To assess the long-term efficacy and safety of anticoagulant therapy (ACT) lasting more than five years in preventing recurrent VTE in patients with stage III-IV ovarian cancer.
Methods. A prospective interventional comparative non-randomized study included 126 women with stage III-IV ovarian cancer. 66 patients with documented VTE received long-term ATC for 60-72 months, while 60 patients without prior VTE were followed as a comparison group. Anticoagulant therapy consisted of direct oral anticoagulants (DOACs): dabigatran 50 mg twice daily, rivaroxaban 10 mg once daily, or apixaban 2.5 mg twice daily. Drug selection was individualized based on renal function, bleeding risk, and comorbid conditions. Patients were followed for thrombotic and hemorrhagic outcomes throughout the observation period.

Results. During long-term follow-up, recurrent VTE was registered in 12 of 66 patients (18.2%) receiving ACT, including DVT in 8 cases (12.1%) and PE in 4 cases (6.1%). The temporal distribution of recurrent events demonstrated that 41.7% occurred within the first 6 months of therapy, an additional 25.0% between 6 and 12 months, and 33.3% beyond the first year, indicating a sustained residual thrombotic risk despite continued anticoagulation. In the comparison group, VTE occurred in 10 out of 60 patients (16.7%) during follow-up, indicating the accumulation of thrombotic events over time in patients with advanced malignancy, even in the absence of prior thrombosis. Bleeding complications in the anticoagulated cohort included major bleeding in 4 patients (6.1%) and clinically relevant non-major bleeding in 14 patients (21.2%). The incidence of hemorrhagic complications remained stable throughout prolonged therapy and did not increase with treatment duration beyond 24 months.

Conclusions. Long-term anticoagulant therapy with DOAC, administered for 60-72 months in patients with advanced ovarian cancer, is associated with a moderate rate of VTE recurrence and an acceptable safety profile. Despite sustained anticoagulation, the highest risk of recurrent thrombosis is observed during the first year of therapy, emphasizing the necessity of prolonged secondary prophylaxis in this high-risk population.