Background

Patients with cancer-associated venous thromboembolism (VTE) are recommended to receive treatment with therapeutic anticoagulation for at least 3-6 months. Little data exists on extended treatment beyond 6 months.

Objective

To comprehensively summarize the best available evidence on incidence of recurrent VTE and major bleeding 6-12 months after the index event in patients with cancer-associated VTE.

Patients/Methods

We systematically screened biomedical databases (Medline, Embase, Central) to identify studies reporting recurrent VTE and/or bleeding events between 6-12 months after a diagnosis of cancer-associated VTE. Based on the observed heterogeneity in study design, setting, patient cohort characteristics, anticoagulation strategies, and outcome rates, no overall quantitative estimate of outcome rates was calculated.

Results

We screened 2,597 publications and identified 11 eligible studies matching pre-defined in-/exclusion criteria, reporting on 3,019 patients specifically during the 6-12-month period post index VTE. Overall rates of recurrent VTE in this timeframe varied substantially (1-12%), with the highest risk observed in the patient subgroup with residual vein thrombosis present at 6 months randomized to receive no anticoagulation (13%-15%). Reported rates of major bleeding between 6-12 months were between 2% and 5%.

Conclusions

In this systematic review, we provide a comprehensive and structured summary of the best available evidence on recurrence and bleeding risk between 6-12 months after cancer-associated VTE. VTE recurrence remains common beyond 6 months and continuation of different anticoagulation strategies has an acceptable safety profile indicated by lower bleeding rates. These findings support guideline recommendations to continue anticoagulation treatment beyond 6 months in patients with active cancer.